2. Mangatawa catchment consents for earthworks, storm water ...

Mangatawa Drain Flood Bypass and TEM 

Stormwater AEE

NZ Transport Agency and Tauranga City Council 

Mangatawa Drain Flood Bypass and TEM Stormwater AEE 

This report has been prepared for the benefit of the NZ Transport Agency (NZTA) and Tauranga City Council 

(TCC). No liability is accepted by this company or any employee or sub-consultant of this company with 

respect to its use by any other person. 

This disclaimer shall apply notwithstanding that the report may be made available to other persons for an 

application for permission or approval or to fulfil a legal requirement. 

Quality Assurance Statement 

Project Manager: Tm Haig 

Prepared by: Michael Seabourne 

Reviewed by: Christine Ralph 

Approved for issue by: Alan Powell 

Revision Schedule 

Rev. 

No 

Date Description Prepared by Reviewed by Approved by 

Status: Final April 2009 

Project Number: 3932036 

NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE




Contents 

1. Introduction........................................................................................................................... 1 

1.1 Background .............................................................................................................. 1 

1.2 Joint Application ....................................................................................................... 2 

1.3 Structure of the Report ............................................................................................. 2 

2. Background............................................................................................................................ 3 

2.1 TEM and State Highway 2.......................................................................................... 3 

2.2 The Mangatawa Drain ............................................................................................... 4 

2.3 Floods in May 2005 .................................................................................................. 4 

2.4 Existing Statutory Approvals ..................................................................................... 5 

2.4.1 TEM Designations previously gained by New Zealand Transport Agency..... 5 

2.5 Current NZTA Programme......................................................................................... 6 

2.5.1 TEM Design and Build Contracts................................................................ 6 

2.6 Current TCC Programme........................................................................................... 6 

2.6.1 Wairakei Catchment .................................................................................. 6 

2.6.2 Maranui and Mangatawa Catchments......................................................... 7 

3. Application Forms .................................................................................................................. 9 

4. Activity Status ...................................................................................................................... 38 

4.1 Regional Water and Land Plan ................................................................................. 38 

4.2 Regional Coastal Plan - Variation of Consent .......................................................... 40 

TCC and TEM Stormwater Treatment Wetland....................................................................... 41 

4.3 District Plan Activity Status ..................................................................................... 41 

Chapter 24: Transportation Activity and Other Network Utility Rules ....................... 42 

Stormwater Treatment Wetland ............................................................................................ 42 

5. Site Description.................................................................................................................... 43 

5.1 The Locality ............................................................................................................ 43 

5.2 Land Use ................................................................................................................ 44 

5.3 Zoning.................................................................................................................... 44 






5.4 State Highway 2...................................................................................................... 45 

5.5 Social Environment ................................................................................................. 45 

5.6 Cultural .................................................................................................................. 45 

5.7 Archaeological........................................................................................................ 46 

5.7.1 Summary of Results ................................................................................ 46 

5.7.2 Archaeological Significance ..................................................................... 46 

5.7.3 General Considerations ........................................................................... 46 

5.8 Topography............................................................................................................ 47 

5.9 Geology.................................................................................................................. 47 

5.10 Ground Conditions ................................................................................................. 47 

5.11 Contaminated Land................................................................................................. 47 

5.12 Land Drainage ........................................................................................................ 48 

5.12.1 Catchments............................................................................................. 48 

5.12.2 Catchment Hydrology.............................................................................. 49 

5.13 Ecology................................................................................................................... 50 

5.13.1 Mangatawa Drain .................................................................................... 50 

5.13.2 Maranui Swale......................................................................................... 51 

5.13.3 Stormwater Treatment Wetland ............................................................... 52 

5.13.4 Special Ecological Site - Salt-marsh and Mangrove (SES) .......................... 55 

5.13.5 Rangataua Bay......................................................................................... 58 

5.13.6 Conclusion.............................................................................................. 59 

6. Alternatives Considered ....................................................................................................... 63 

6.1 Further Engineering Options Considered................................................................. 64 

6.1.1 Outlet and Discharge Points .................................................................... 65 

7. Description of the Proposal ..................................................................................................67 

7.1 Mangatawa Flood Bypass Activities ......................................................................... 67 

7.1.1 Increased Drain Storage .......................................................................... 67 

7.1.2 Top Spill Bund......................................................................................... 67 

7.1.3 Bruce Spill Stop Bank............................................................................... 67 

7.1.4 Maintenance Work in Upper Mangatawa Drain ......................................... 68 

7.1.5 Rail Bridge Embankment Stability ............................................................ 68 

7.1.6 Flood Bypass from Maranui to Mangatawa ............................................... 69 

7.1.7 Sandhurst Culvert ................................................................................... 69 

7.1.8 Extension of Maranui Culverts ................................................................. 69 

7.1.9 Maranui Swale Deepening........................................................................ 69 

7.1.10 Lower Mangatawa Drain (from Mangatawa Lane to Tauranga Harbour)..... 70 

7.1.11 Mangatawa Flood Bypass Flood Levels ..................................................... 70 






7.1.12 Stormwater Treatment Wetland ............................................................... 71 

7.2 TEM Roadway Stormwater ....................................................................................... 73 

7.2.1 TEM Stormwater Management Philosophy................................................ 73 

7.2.2 Swales..................................................................................................... 73 

8. Consultation ........................................................................................................................ 75 

8.1 Background – Tauranga Eastern Motorway .............................................................. 75 

8.1.1 Consultation Objectives .......................................................................... 75 

8.2 Mangatawa Public Consultation............................................................................... 75 

8.3 Directly Affected Landowners.................................................................................. 76 

8.4 Individual Landowners ............................................................................................ 76 

8.4.1 MPBI........................................................................................................ 76 

8.5 Tangata Whenua ..................................................................................................... 78 

8.5.1 TEM Project Hui....................................................................................... 78 

8.5.2 Mangatawa Floodway Application Hui...................................................... 79 

8.5.3 Tauranga Eastern Motorway Tangata Whenua Advisory Group ................. 81 

9. Assessment of Environmental Effects ................................................................................... 82 

9.1 Stormwater Management ........................................................................................ 82 

9.1.1 Water Quantity ........................................................................................ 82 

9.1.2 Water Quality .......................................................................................... 83 

9.1.3 Freshwater Ecology ................................................................................. 86 

9.2 Earthworks ............................................................................................................. 89 

9.2.1 Ecological Effects from Construction ....................................................... 89 

9.2.2 Noise and Vibration................................................................................. 91 

9.2.3 Dust........................................................................................................ 91 

9.2.4 Archaeological Effects from Construction ................................................ 92 

9.2.5 Hazardous Substances/Contamination/Probability of Risk ....................... 93 

9.3 Assessment of Stormwater and Earthworks Cultural Aspects ................................... 93 

10. Statutory Assessment........................................................................................................... 95 

10.1 RMA 1991 .............................................................................................................. 95 

10.2 Bay of Plenty Regional Policy Statement (RPS) .......................................................... 98 

10.3 Operative Regional Water and Land Plan (RWLP) – 1 st December 2008.................... 100 

10.4 Bay of Plenty Regional Air Plan .............................................................................. 102 

10.5 Regional Coastal Environment Plan Coastal July 2003............................................ 102 

10.6 Tauranga District Plan........................................................................................... 103 






10.7 Wairakei Urban Development Comprehensive Stormwater Consent........................ 106 

11. Conclusion......................................................................................................................... 107 

11.1 Mangatawa Flood Bypass ...................................................................................... 107 

11.2 TEM Stormwater Management............................................................................... 107 

11.3 Earthworks ........................................................................................................... 108 

11.4 Statutory Conclusion............................................................................................. 108 

List of Figures 

Figure 1: TEM Layout......................................................................................................................3 

Figure 2: Approximate Location of Proposed Works......................................................................43 

Figure 3 Positions of Sampling Stations within the Stormwater Treatment Wetland Area.................55 






List of Tables 

Table 1: Regional Consents required and ownership status of each consent .................................38 

Table 2: Regional Coastal Environmental Plan Consents Required and Ownership Status of each 

Consent ................................................................................................................................41 

Table 3: TCC District Plan General Natural Resource Rules - Maintaining Biodiversity and Protecting 

Ecosystems ...........................................................................................................................41 

Table 4: District Consents Required .............................................................................................42 

Table 5: Rangataua Bay Catchment Sediment Quality Results........................................................51 

Table 6: Species of Birds Observed utilising the wetland and their Principal Habitats ....................54 

Table 7: Sampling Site Locations ..................................................................................................57 

Table 8: Results of Rangataua Bay Sediment Quality Analyses.......................................................58 

Table 9: Summary of Ecological Characteristics ............................................................................60 

Table 10: Hydraulic Results 1% AEP ..............................................................................................71 

Table 11: Stormwater Treatment Requirement..............................................................................72 

Table 12: Summary of Issues Raised.............................................................................................77 

Table 13: Contaminant Discharge Summary ..................................................................................85 

Table 14: Maximum Permitted Ground Vibration Levels................................................................91 

Appendices 

Appendix 1 – Drawing 3932036 ck301 Rev C 

Appendix 2 – Extract from the Tauranga District Plan: Special Ecological Site 13 

Appendix 3 – Drawing 3932036 ck119 Rev F 

Appendix 4 – Drawings 3932036 ck073 Rev G, ck074 Rev E, ck075 Rev F 

Appendix 5 – Bioresearches Report: Ecological Features of some Habitats within Rangataua Bay 

Catchment 

Appendix 6 – Ngaiterangi Cultural Impact Assessment 

Appendix 7 – Archaeological Assessment: Te Maunga to Domain Road, Archaeology BOP 

Appendix 8 – Hydraulic Modelling: Mangatawa Drain/Maranui Swale – Mitigation Options 

Appendix 9 – Drawings 3932036 ck143 Rev C, ck144 Rev E, ck145 Rev E, ck146 Rev E, ck473 

Rev A 

Appendix 10 – Drawings 3932036 ck460 Rev A, ck461 Rev A, ck462 Rev A, ck467 Rev A, ck468 

Rev A, ck469 Rev A 

Appendix 11 – Drawing 3932036 ck431 Rev B 

Appendix 12 – Drawing 3932036 ck227 Rev D 

Appendix 13 – Example Erosion and Sediment Control Plan 

Appendix 14 – Regional Water and Land Plan Activity Status, Rules, Policies and Objectives 

Appendix 15 – Legal Descriptions of Land Parcels Affected by Construction 

Appendix 16 – Existing TCC Discharge Consent Nº 60061 






1. Introduction 

This report seeks consent for the proposed stormwater management activities resulting from the 

construction of the Tauranga Eastern Motorway (TEM) and consent for activities resulting from Tauranga City 

Councils desire to address flooding issues in the Mangatawa catchment. 

Applying for The Environment Bay of Plenty consents jointly allows the New Zealand Transport Agency (NZTA) 

and Tauranga City Council (TCC) to develop a solution that addressed a complex stormwater management 

issue in an efficient manner. This assessment of environmental effects therefore considers the effects of all 

the activities related to this project including construction. 

In addition the proposal also requires District Council consents related to the proposed alteration to the 

stormwater treatment pond including vegetation clearance, earthworks and discharge to the adjacent Special 

Ecological Site. The bundle of regional resource consents sought is divided in the following way: 

• NZTA permit holder for construction aspects; 

• TCC permit holder for long term elements particularly discharges; and 

• The District Council land use consent will run with the land on which the treatment pond is placed. 

1.1 Background 

NZTA is planning to build the TEM, as part of providing transport infrastructure for the ongoing growth of 

Tauranga and the Bay of Plenty. In November 2008 the NZTA applied to the Regional Council for consents for 

earthworks, water take, bridging the Kaituna River and stormwater management excluding this catchment. 

The Hearing was completed on the 18th of December 2008 and a decision has been received. 

TCC manages the stormwater system in urban Papamoa, and needs to reduce the frequency and magnitude 

of spills from the Papamoa Hills and Mangatawa Drain into the Papamoa urban area, where there would 

otherwise be a risk of inundation of many buildings in large floods. 

This application seeks consent to manage the stormwater derived from the proposed motorway. NZTA and 

TCC are working together to improve the reliability of the route by reducing the frequency of flood overflows 

of State Highway 2 (SH2) from the Papamoa Hills and the Mangatawa Drain. 

Beca has been working with both NZTA and TCC, investigating options for reducing the frequency and 

magnitude of spills from the Mangatawa Drain. As this work has progressed, various options have been 

considered and preferred options refined and modelled to confirm their performance. 

Status: Final Page 1 April 2009 





1.2 Joint Application 

This report will assess the combined effects of this project. The various consents required need to be held 

separately by either NZTA or TCC for the purposes of clearly assigning responsibilities for the effects of these 

activities. The consent requirements are split between Tauranga City Council and the New Zealand Transport 

Agency. It is important to understand that in the issuing of any consent, the Regional Council will be 

assigning the responsibility for the effects of the activities related to those consents to either NZTA or TCC. 

The split has been decided and agreed upon by both the organisations applying for consents. 

1.3 Structure of the Report 

The key sections of this report are the description of the proposal which is found in Section 7 and the 

assessment of the environmental effects in Section 9. 






2. Background 

2.1 TEM and State Highway 2 

SH2 is the major road access to Tauranga from the south east – Te Puke, Rotorua, Whakatane, Opotiki, 

Gisborne. SH2 at this location is categorised as a national function State highway by the NZTA, based on 

traffic flows, vehicle composition and the nature of destinations it connects with. It is the main route for 

heavy commercial vehicles heading to the Port of Tauranga from Rotorua and the Eastern Bay of Plenty, 

connecting the economically important central plateau forestry industry with the export port of Tauranga. 

The NZTA is responsible for the TEM and this is a key component of the Tauranga Eastern Transport Corridor. 

The Tauranga Eastern Corridor is the transportation network required to service the existing and predicted 

inter-regional traffic as well as the urban growth of Papamoa East. Papamoa East is the largest growth area 

of the Western Bay of Plenty sub-regional SmartGrowth strategy. The attached Figure 1 shows the layout of 

the TEM in relation to the SmartGrowth land use areas for the eastern corridor. 

Figure 1: TEM Layout 






The urban growth area of Papamoa is predicted to become a city the size of Nelson (40,000 pop.) by 2050. A 

large industrial park is being planned inland from Papamoa East. These developments are designed to 

provide for residents to live, work and play in the area, reducing commuter travel, but there is still a need for 

additional capacity on the inter-regional corridor. 

Currently, traffic volumes on SH2 are up to approximately 21,000 vehicles a day, and the road has a high 

crash rate. The New Zealand Road Assessment Programme (KiwiRAP) has ranked this section of SH2 between 

Te Maunga and Paengaroa as having the second highest number of fatal and serious injury crashes per 

kilometre of State highway in New Zealand. 

Travel times are constrained, with limited capacity for growth. Traffic through Te Puke’s central business 

district is also heavy, and conflicts with local traffic causing safety concerns and an increase in waiting times 

at intersections. There are safety concerns at the Waitangi Township to the east of Te Puke. 

NZTA has the statutory objective under the Land Transport Management Act (2003) to ‘operate the State 

highway system in a way that contributes to an integrated, safe, responsive and sustainable land transport 

system’. The construction of the TEM as part of the Tauranga Eastern Corridor achieves this objective. 

2.2 The Mangatawa Drain 

Tauranga City Council is responsible for managing stormwater so that property and people are protected 

from flood damage, and to minimise adverse effects on the harbour and waterways from stormwater run-off. 

The flooding issue that Council is seeking to resolve is historically associated with the spills across the State 

highway from the Mangatawa Drain. 

The Mangatawa Drain was constructed many years ago, reportedly when the railway was built along the route 

parallel to what is now SH2. The purpose of the drain was to divert flow that previously flowed north into 

what was at the time farm land but is now Papamoa urban area. 

The Mangatawa Drain is about 2,500m long where it is alongside the proposed TEM. The drain is a 

vegetated, earth lined channel that is tightly constrained between the railway (to the south) and the motorway 

(to the north). There is some uncertainty as to who owns the land and is responsible for its maintenance, 

although in the past Tauranga City Council has undertaken maintenance. It is predominantly on railway land 

and partly on road reserve. 

In larger flood events, excess flow spills north across the State highway at two locations into the Papamoa 

urban area. The two locations are identified in this report as “Top Spill”, located near Kairua Road and “Bruce 

Road Spill”, located just west of Bruce Road (although the spill covers several hundred metres of highway in 

the general vicinity of Bruce Road). 

2.3 Floods in May 2005 

In the 18 May 2005 storm extensive ponding occurred in the Papamoa area. The Mangatawa Drain alongside 

the motorway overflowed at two locations. Opus was initially appointed by TCC to undertake investigations 






into the drain performance. They produced three reports 1 and the last was after the May 2005 floods. As part 

of their work a MIKE11 hydraulic model was built. New Zealand Transport Agency (NZTA) has been working 

with TCC to find a solution which will avoid or at least reduce overflows. The aim for NZTA was to avoid if 

practicable the 1% annual exceedance probability (AEP) storm event overtopping and overflowing the 

motorway, while TCC’s aim was to reduce the volume of water that would enter the Papamoa catchment areas 

(Maranui Swale and the Wairakei Stream) such that the design flood level for Papamoa of 4.5m RL (Moturiki 

Datum), as defined in the District Plan, was not exceeded in the 2% AEP storm event. Beca was appointed to 

adopt the Opus hydraulic model and undertake further modelling and engineering work to investigate 

mitigation options, as an extension to the work they were carrying out for NZTA on the TEM. 

2.4 Existing Statutory Approvals 

Currently there are no resource consents for the management of stormwater generated by State Highway 2 or 

for the Mangatawa drain discharge to the Tauranga Harbour. However the Mangatawa Drain is defined as 

Land Drainage canal in the Regional Water and Land Plan 2 . 

The TCC treatment wetland that receives stormwater from the Maranui catchment has consent for discharge 

which needs to be varied as part of this application. 

The over spill into the Wairakei catchment is currently covered by the Wairakei Catchment comprehensive 

consent which is currently subject to appeal. 

2.4.1 TEM Designations previously gained by New Zealand Transport Agency 

The designated corridor for the motorway has been in place since 2004 and was designated in four parts. It 

consists of designations for: 

• Te Maunga Four Laning 

• Te Maunga Service Roads 

• Sandhurst Interchange 

• Tauranga Eastern Arterial. 

The designations are now collectively referred to as the TEM. The designations that relate to this project area 

are Te Maunga four laning and Sandhurst Interchange. 

1 Mangatawa Drain Flood Capacity, September 2000; Mangatawa Drain Flood Capacity: Supplementary Report, July 2001; 

and Mangatawa Drain Flood Assessment, 29 November 2006; all produced by Opus International Consultants Ltd 

2 RWLP Dec 2002, Definitions Chapter, Pg 436. Land Drainage Canal. 






2.5 Current NZTA Programme 

Work has progressed since the corridor was designated. The design of the TEM has advanced to allow NZTA 

to understand the potential effects and to apply for Resource Consents related to the construction of the 

TEM. The next step is to develop Specimen Design and Principal’s Requirements to be used in a contract 

specification to go to tender with. It is anticipated that if Resource Consents are gained and funding 

confirmed, tendering may occur in 2009 with a possible construction start in 2010. 

2.5.1 TEM Design and Build Contracts 

For this project a design and build contract will be used, similar to that employed in the Harbour Link Project 

in Tauranga. A design and build contract is structured to encourage innovation and cost saving in the 

construction of the project. It works by establishing in contract documentation the environmental and 

engineering outcomes and performance criteria for the proposed project. These criteria form the limits in 

which the contractor must perform but allows the contractor to use their experience to suggest new and 

innovative methods for achieving the same outcome. It gives the necessary certainty and flexibility to the 

process so that the environmental, engineering and economic outcomes can be achieved whilst allowing cost 

savings to be made. 

The consent process will set the environmental bottom lines for this project that the contractor will be 

required to adhere to. 

2.6 Current TCC Programme 

Territorial authorities in the Bay of Plenty Region are required to prepare Comprehensive Stormwater 

Consents and Management Plans for existing urban areas and areas identified for future development. The 

Regional Stormwater Strategy has identified 11 comprehensive catchments in Tauranga City each requiring a 

consent with lodgement dates from 2006 through to 2010. TCC has applied for the first of these 

comprehensive catchment consents (for Papamoa/Wairakei Catchment discussed in clause 2.6.1 2.6.2 below) 

and is currently working with Environment BOP to review the number of comprehensive catchments and 

prepare a revised programme for lodging the consent applications. 

2.6.1 Wairakei Catchment 

An application for the Papamoa/Wairakei Comprehensive Catchment was lodged with Environment BOP in 

2006 and is being processed in conjunction with the Papamoa East (Wairakei) Plan Change. The application 

has been required to consider not only the current urban area but the full urbanization of the Wairakei and Te 

Tumu areas over the next 50 years. 

The key issue has been flood management in a catchment with a limited outlet to the ocean. The long term 

proposal is a high level outlet to the Kaituna River to be constructed in conjunction with the commencement 

of the development of the Te Tumu area around 2021. In order to manage high winter water levels in the 

existing rural land in Te Tumu in the interim pumping excess water to the Kaituna is proposed. 






While the plan change appeals have not yet been entirely resolved, the majority of the plan change has been 

accepted and is expected to be resolved in the near future. Key to this application is that spills in to the 

Wairakei catchment from the Mangatawa catchment across the state highway have been planned and 

accommodated in this comprehensive consent. This design level or amount of flooding has influenced the 

design of the Mangatawa Drain flood way structures that will be described further in this report. 

2.6.2 Maranui and Mangatawa Catchments 

For the purposes of this application two stormwater catchments; the Mangatawa and Maranui are affected by 

the Tauranga Eastern Motorway (TEM) and the Mangatawa Drain Flood Bypass Structures. A central issue in 

these catchments and for the TEM project is the flooding across the State highway and subsequently the 

effects of flooding in the Maranui sub catchment and Wairakei catchment. 






3. Application Forms 

See notes to applicant (last pages of form) before 

proceeding with application form. 

Pursuant to section 88 of the Resource Management Act 1991, the undersigned hereby 

makes application for resource consent(s). 

1 Full name of applicant(s): 

This is a joint application – Refer to Table 1 for permit holder for each consent 

Company Name: 

New Zealand Transport 

Agency 

Tauranga City Council 

Contact Person: Kevin Reid Graeme Jelley 

Postal Address: 

PO Box 430, Seventh 

Avenue, Tauranga 3140, NZ 

91 Willow Street, Private Bag 

12022, Tauranga 3110, NZ 

Business phone: 07 9276009 07 577 7000 

Facsimile number: 07 578 2909 07 571 8917 

Email: kevin.reid@nzta.govt.nz graeme.jelley@tauranga.govt.nz 

2 Details of consultant 






Company Name: 

Contact person: 

Postal address: 

Beca Infrastructure Limited 

Christine Ralph / Mike Seabourne 

32 Harington St, PO Box 903, Tauranga 

Business phone: 07 578 0896 

Email: 

christine.ralph@beca.com, michael.seabourne@beca.com 

All correspondence (including invoices for charges) relating to this application(s) should be 

sent to: 

Applicant: 

Consultant: 

3 Name and address of owner/occupier of the site relating to application 

The legal descriptions of the site are contained in Appendix 15 

4 Consent(s) being applied for from Environment Bay of Plenty: 

Land use 

Form 1 

Beds of lakes and rivers (use, place, alter or remove structure in river, 

stream or lake; disturb bed of river, stream or lake (excluding shingle 

extraction); deposit substance in on or under bed of river, stream or 

lake). 

Form 2 Land disturbing activities (earthworks, quarrying, vegetation clearance / 

harvesting / burning) 

Form 3 

Shingle extraction 

Water (including coastal) 

Form 4A 

Form 4B 

Form 5 

Form 6 

Take surface water (includes intake structure) 

Take groundwater 

Dam/divert/use water 

Geothermal - take and discharge 

Discharge (including coastal) 

Form 7 

Form 8 

Form 9 

Discharge contaminant to air 

Discharge contaminant or water to water 

Discharge contaminant to land 






Form 10 

Form 11 

Onsite effluent discharge 

Discharge farm dairy effluent 

Coastal (see point 4 of information sheet for explanation of the coastal marine area). 

Form 12 

5 Location description of activity: 

General (occupancy; disturb foreshore or seabed; plant foreshore or 

seabed; deposit substance, remove natural material, reclaim or drain; 

place, remove or alter structure). 

On or generally about the State Highway 2 between the end of Truman Lane and Domain 

Road. This includes lands owned by Mangatawa Papamoa Blocks Incorporated near or 

about the Mangatawa Drain to the Tauranga City Council Stormwater Wetland. 

Site plan 

Please provide a site plan showing any works relating to the proposal, area surrounding the 

site including the names of current owners and occupiers of adjoining property. A lot map 

from the district council will assist in identifying potentially affected parties. 

• See description of the environment provided in application 

6 In which district is the activity located: 

Tauranga District 

Do you also require resource consent(s) from a district council? Yes No 

Type of consent required: 

• Significant amounts of earthworks and vegetation removal are required as part of the 

proposal. These activities are non complying activities subject to Rule 14.1 (b) and (c) of 

the Tauranga District Plan 

• Stormwater detention ponds and associated earthworks and structures under Table 24-1 

in the Industrial Business Zone are controlled activities. 

Have these been applied for? 

• These activities will be applied for as part of this application 

7 Refer to relevant activity form. 

• Form 1, Form 2, Form 5, Form 8, Form 9 

8 Is this application to replace an existing or expired consent? 

Yes 

9 Duration of consent 

No 

• Please see Table 1 for consents being applied for and duration of those consents. 

10 DEPOSIT FEE 

A deposit fee of $774.00 (including GST) is payable with this application. A GST invoice 

marked ‘PAID’ will be issued on receipt of payment. Processing of the application will not 






begin until the deposit fee has been paid. Additional charges are usually incurred for the 

majority of consents that are not minor. Staff can give an indicated range of expected costs. 

Important Note 

Information Privacy Issues 

The information you provide in this application is regarded as official information. It is 

required under the provisions of the Resource Management Act 1991 to process this 

application and to assist in the management of the regions natural and physical 

resources. 

The information will be held by Environment Bay of Plenty, Quay Street, Whakatane. 

This information is subject to the provisions of the Local Government Official 

Information and Meetings Act 1987 and the Privacy Act 1993. 

Failure to provide this information will mean that Environment Bay of Plenty will be 

unable to process your application. 

I have read and understand all of the information contained on this application form 

including the requirement to pay additional costs that will be itemised. 

Signature ______________________________________ Date 

_______________________ 

Signature ______________________________________ Date 

_______________________ 






Form 1 

Beds of lakes and rivers 

Question 7 

Assessment of effects on the environment (AEE) 

Section 88 of the Resource Management Act 1991 requires all applications for 

resource consents to include an assessment of the actual or potential effects that the 

proposed activity may have on the environment and the ways in which any adverse 

effects can be mitigated. The Fourth Schedule of the Act lists the matters that should 

be included in such assessments and a summary is printed on the back of the 

application form. 

You must fully complete this section or your application cannot be processed. 

The information you supply should be detailed according to the scale, scope and 

effects of the proposed activity. 

Applicants for small scale proposals having minor effects should be able to supply 

sufficient information by filling in the spaces provided. More complex proposals with 

more significant effects will need to address the following matters (in accordance with 

the Fourth Schedule) as a separate document. 

If the AEE is presented in the format of a report, it must address the following matters, 

if appropriate. 

If you are unsure how to complete this section please contact an environmental 

consents officer at Environment Bay of Plenty. 

1 Description of activity (tick appropriate box) 

Use erect / reconstruct / place / alter / extend / remove or demolish any structure or 

part of any structure in, on, under, or over the bed. 

Excavate, drill, tunnel, or otherwise disturb the bed 

Introduce or plant any plant or any part of any plant (whether exotic or indigenous) in, 

on, or under the bed 

Deposit any substance in, on, or under the bed 

Reclaim or drain the bed 

Other 

Please describe the proposed activity in detail (dimensions, purpose, materials to be used, 

reason for the works) 

See application 






Please provide: 

a) Structural plans, to scale on good quality paper of minimum A4 size. Show side view 

and plan view. 

b) Design details and calculations. 

Please describe how the construction / disturbance / removal will be carried out (e.g. 

machinery to be used, access to site, staging of works etc) 


c) A cross section of the proposed site. 

d) Cross sections 50 metres upstream and downstream of the site. 

Note: A cross section involves the following measurements: 

• the width between the top of each bank. 

• the width across the bed of the waterway 

e) The height of each bank above the bed of the waterway. 

2 Description of site 

Describe the physical attributes of the sites e.g. topography, ecology, bed materials, wildlife 

habitats, cultural, scientific features. It would be useful to include photographs. 


Please provide any hydrological data, if available. These include: stream flow and gradient, 

catchment size in hectares and catchment characteristics, e.g. steep, forested catchment or 

easy pastoral catchment. 


3 Assessment of effects 

Describe the actual or potential effects that the proposed activity / operation could have on 

the environment 

Effects of immediate activity / construction: 


Effects of the completed works or structure on the riverbed both upstream and 

downstream: 


Effects on fish passage: 







Effects of the works/structure in extreme events (e.g. flooding). Please provide an 

assessment and any supporting calculations: 


Any other effects: 


What methods or actions will be used to reduce or prevent any identified environmental 

effects. e.g. grassing and planting of fill batters, metalling of approaches, stabilisation of 

abutments by crib walling. 


Assessment of any alternative options considered and reasons why these are not proposed: 


Details of any monitoring proposed: 


4 Persons likely to be directly affected: 

For your application to be considered for non-notification, you must gain the written approval 

of all persons who may be affected by the proposal. Please specify below those parties who 

may be affected (or interested by your proposal). 

Persons who may be interested or affected and consultation undertaken 

State any contact made with neighbouring land owners and occupiers and organisations 

such as the Department of Conservation, Eastern Region Fish and Game Council, local iwi 

and community groups. Where possible, record any comments made by these parties and 

outline your response to them. A list of people and organisations who you consider may be 

interested or affected should also be supplied wherever possible. 


Note: Environment Bay of Plenty can provide a form for the written approval of affected persons. 






Form 2 

Land disturbing activities 

(earthworks, quarrying, vegetation 

clearance, harvesting, burning) 

Question 7 


Section 88 of the Resource Management Act 1991 requires all applications for resource 

consents to include an assessment of the actual or potential effects that the proposed 

activity may have on the environment and the ways in which any adverse effects can be 

mitigated. The Fourth Schedule of the Act lists the matters that should be included in such 

assessments and a summary is printed on the back of the application form. 


The information you supply should be detailed according to the scale, scope and effects of 

the proposed activity. 

Applicants for small scale proposals having minor effects should be able to supply sufficient 

information by filling in the spaces provided. More complex proposals with more significant 

effects will need to address the following matters (in accordance with the Fourth Schedule) 

as a separate document. 

If the AEE is presented in the format of a report, it must address the following matters, if 

appropriate. 

If you are unsure how to complete this section please contact an environmental consents 

officer at Environment Bay of Plenty. 

1 Description of the proposal 

a) What is the nature of the activity you propose to undertake? 

• Activity related to the management of TEM stormwater and associated works. 

• Activity related to Flood mitigation measures for the Mangatawa catchment and associated 

works 

• Also see “Description of the Proposal” and “Construction Methodology” in application. 

b) What is the scale of the proposal? 

The Earthworks required for the TEM project has been applied for in a previous application. The 

earthworks required for this application are associated with the Mangatawa Floodway construction 

and Stormwater wetland construction and are referred to specifically in the text of this document. 

The total volume of earthworks required to be undertaken is approximately between 45,000m³ - 

60,000m³ for the TEM component of the works only. See section 9.2. 






c) When will the activity be undertaken, and for how long will it occur: 

The design of the Motorway has advanced to allow NZTA to understand the potential effects of 

constructing the Motorway and to apply for Resource Consents related to the construction of the 

Motorway. The next step is to develop Specimen Design and Principal’s Requirements to be used 

in a contract specification to go to tender with. It is anticipated that if Resource Consents are 

gained and funding confirmed, tendering may occur in 2009 with a possible construction start in 

2010. 

d) Proposed works and construction methods: 

• See “Description of the Proposal” and “Construction Methodology” in application. 

e) Details of engineering design associated with proposal: 

(include calculations and plans if appropriate) 

• See project description in application 

f) Cross sections/long sections of any cut/full areas over 2.0 metres in height: 

• See application and appendices 

2 Description of the receiving environment 

Our environment is made up of many components. Completing this section helps identify issues 

relating to the proposal. Please describe the following aspects of the environment in the immediate 

vicinity of the proposal and locate/identify them on a map where practical. 

2.1 Description of the natural environment 

a) Geology and soils (described in detail to at least 1 metre depth below the expected maximum 

excavation): 

• See description of the environment in application 

b) Upstream and Downstream Catchment characteristics: 

Watercourses/Coastal Marine Area (name, size, proximity to proposal, perennial or ephemeral): 


Drainage patterns/size of catchments: 


c) Topography (identify sloping areas, gullies, steep erodible features): 


d) Vegetation types/values: 


e) Ecological features (including vegetation type and extent, the presence of fauna): 







f) What is the nature of the watercourses and receiving environment, in terms of water quality? 


2.2 Description of the human and built environment 

a) Any built structures such as bridges, culverts, roads, buildings etc: 


b) Neighbours (location/proximity to proposal): 


2.3 Natural and cultural heritage 

a) Does the receiving environment or site have any natural or cultural heritage values (e.g. 

archaeological/historic sites, significant landscapes – give location/proximity to proposal)? 


b) Does the receiving environment or site have any amenity values (consideration should be given to 

the recreational use of the site and the receiving environment)? 


d) Have you consulted with Tangata Whenua? (consultation with Tangata Whenua is important in 

determining any values that may be present on the site and within the receiving environment, and 

how these can be managed): 


e) Is the proposed activity located in an area of significant natural heritage identified in the Bay of 

Plenty Regional Council’s Regional Policy Statement or Regional Plans? 


3 Effects of the proposal 

a) Describe the actual or potential effects that the proposal may have on the environment (Having 

considered all of the above matters, how will the proposed activity affect the values of the receiving 

environment and site? e.g., sediment contaminants, dust, natural and cultural heritage values, 

Tangata Whenua values, Amenity values, landscape areas or other contaminants): 

• See assessment of effects in application 

b) What is potential erodibility of the soils of the site: 


c) What is the estimated sediment generating potential of the site (this should include an assessment 

of slopes greater than 10 degrees with aspects not north facing): 







4 Methods used to avoid/remedy or mitigate these environmental effects 

For each of the effects identified above, describe the measures you will take to avoid / reduce / 

remedy them: 


4.1 Erosion and sediment control plans 

Erosion and sediment control plans must establish clearly which control measures are intended to 

prevent erosion and off site sedimentation and how they relate to the proposal. Making the effort 

to produce comprehensive plans which are easy to follow (e.g. use colour for cut/fill areas, extent 

of earthworks etc) will save time and money in processing the application. 

The information included in erosion and sediment control plans should correspond to the scale and 

significance of the proposal. Small–scale proposals having minor effects may supply sufficient 

information by drawing a sketch plan in the space provided. For more significant proposals, 

detailed plans should be drawn to show the erosion and sediment control measures intended for 

each stage of the proposal. 

Refer to Environment Bay of Plenty erosion and sediment control guidelines for earthworks. 

• See description of the proposal and appendices application 

a) Schedule of Works 

Describe the estimated timing of each stage of the earthworks including the installation/removal of 

erosion and sediment controls, and any other relevant works. 

Stage 

Description 

Expected Start 

Date 

Expected 

Completion 

Date 

1 See description of the proposal in application 2010 2015 

b) What erosion control measures are proposed and what are the expected efficiencies of these 

measures? 


c) What sediment control measures are proposed and what are the expected efficiencies of these 

measures? 


4.2 Dust control plan 






Dust control plans must establish clearly which control measures are intended to prevent 

emissions of dust particulates. Making the effort to produce comprehensive plans which are easy 

to follow will save time and money in processing the application. 

The information included in dust control plans should correspond to the scale and significance of 

the proposal. 

a) What dust control measures are proposed and what are the expected efficiencies of these 

measures? 


5 Alternatives and mitigation 

a) Where it has been determined that the proposed activity will result in a significant adverse effect on 

the environment, can the impacts of the proposed activity be reduced or avoided by adopting an 

alternative methodology, or changing the end use of the site? 


6 Monitoring 

a) What, if any, monitoring do you propose to carry out to ensure that the discharge does not have 

any adverse effect? 



For your application to be considered for non-notification, you must gain the written approval of all 

persons who may be affected by the proposal. Please specify below those parties who may be 

affected (or interested by your proposal). 

• See consultation section in application 








Form 5 

Dam / divert / use water 

Question 7 















appropriate. 



Part A: To dam water 

Part B: To divert water 

Part B — To Divert Water 

1 Is the diversion: 

existing 

or proposed? 

If the diversion relates to a new activity a land use consent may also be required. 

If the diversion is in the coastal marine area a coastal permit to divert water is required. You can 

make the application on this form. A coastal permit to erect any structures and occupy the coastal 

marine area is required for a new diversion. 

2 Why are you diverting water? 






(e.g. stormwater control, river works, stream realignment, etc.) 

• To control the spill of flood waters over the State Highway at 2 locations - See application and 

appendices for details. 

3 What is the name of the watercourse to be diverted? 

• Mangatawa Drain 

4 What is the rate at which water will be diverted? 

• The flow rate of the diversion is not a significant effect of this activity and does not need to be 

assessed in this manner. The application project description and AEE sections will outline the 

effects of this application. 

5 Will the diversion be: 

intermittent 

or continuous? 

If intermittent, what will be the maximum operating period? 


6 Does the diversion also involve: 

Taking water? 

Yes 

No 

Damming water? 

Yes 

No 

Discharging? 

Yes 

No 

Any Structures? 

Yes 

No 

If you answered Yes to any of 6 above, a separate consent application may be required. 

7 Where your diversion could have a significant adverse effect on the environment a more detailed 

environmental assessment is required in accordance with the Fourth Schedule of the Resource 

Management Act 1991. 

7.1 Will the diversion have an effect on water availability to downstream users and/or affect access to 

neighbouring properties? 

Yes 

No 






7.2 Within a reasonable distance up or downstream of the diversion are there any: 

1 Obvious signs of biota Yes No 

(e.g. fish, eels, insect life, aquatic plants)? 

2 Areas where food is gathered from the stream Yes No 

(e.g. watercress, eels, wild fowl, kaimoana)? 

3 Wetlands Yes No 

(e.g. swamp areas)? 

4 Waste discharges Yes No 

(e.g. from rural sources, industries, sewerage plants, etc)? 

5 Recreational activities carried out Yes No 

(e.g. swimming, fishing, canoeing)? 

6 Areas of particular aesthetic or scientific value Yes No 

(e.g. scenic waterfall, rapids, archaeological sites)? 

7 Areas or aspects of significance to Iwi? Yes No 

7.3 If you have answered yes to 7.1 and any part of 7.2 above, describe what adverse effects your 

diversion may have and the steps you propose to take to mitigate these. If the adverse effect is 

significant describe alternative locations or methods you have considered for undertaking the 

damming. 

• See assessment of effects section in application 

8 Have you provided any means for fish to bypass the diversion 

(e.g. fish ladders, elver tubes, etc) 

Yes 

No 

Please describe: 

• Existing fish passage will not be impeded by this proposal. See assessment of effects section 

in application for details. 

9 Describe the bed of the watercourse in the vicinity of the diversion site 

(e.g. is it gravelly, muddy or sandy?) 

• The bed of the Mangatawa Drain is predominantly sandy. See assessment of effects section in 

application for details. 

10 Will the diversion cause flooding or other problems to neighbouring properties? 

Yes 

No 

Please describe: 






• The incidence of flooding should decrease generally. See assessment of effects section in 

application for details. 

11 Please attach your calculations which show that the diversion design is adequate, including 

design flood flows, return periods, etc. 

• See Mangatawa drain options report in application appendices 

12 Have you discussed your diversion with any potentially affected parties? 

(e.g. neighbours, water users, the Fish and Game Council, Department of Conservation, etc.) 

Yes 

No 













Form 8 

Discharge contaminants or water to water 

Question 7 















appropriate. 



1 Description of activity 

a) Where are discharged contaminants sourced from? (tick as appropriate) 

Sewage treatment plant, servicing 

Industrial premises, (specify type) 

Water treatment 

Other (specify) State highway 

If you ticked sewage treatment plant or industrial plant or industrial premises give description of 

type of process. 

2 Nature of the discharge and sensitivity of receiving environment 

a) Describe the contaminant including, where appropriate: 

Temperature: See project description in application 

pH: 

See project description in application 






Suspended Solids: 


BOD5: 


Faecal Coliforms: 


Enterococci: 


The chemical content, including heavy metals or toxic substances, nitrates, ammonia and 

dissolved reactive phosphorus: 


b) Is the contaminant treated in any way before discharge? 

Yes 

No 

If Yes, describe treatment 


c) What is the name of the water body into which the discharge is made (e.g. at the discharge site 

name of stream, river, lake, bay, harbour)? 

• Rangataua Bay, Tauranga Harbour 

Is this in the coastal marine area? Yes No 

What is the water quality in the water body? 

• See project details in application for details 

d) Discharge rate information: 

• For the details regarding Maximum flow rate, Maximum daily flow, Average dry weather flow 

and Average wet weather flow, please see the project description in the application. 

For non stormwater discharges, is the discharge: N/A 

What will be the maximum discharging period? 

• See project description in application for details. 

e) Does the discharge also involve: diversion of natural water Yes No 

discharge to air Yes No 

piping across a waterway or water body Yes No 

any structure in waterway or water body Yes No 






If you answered Yes to any of the above, a separate consent application may be required. 

3 Assessment of effects on the environment 

Where your discharge could have a significant adverse effect on the environment a more detailed 



a) Comment on the possible effect the discharge may have on the quality of the receiving 

environment and users: 


b) Within a reasonable distance downstream, down groundwater gradient or in the vicinity of the 

discharge are there any: 

1 Obvious signs of biota (e.g. fish, eels, insect life, aquatic plants) Yes No 

2 Areas where food is gathered Yes No 

3 Water abstractions Yes No 



6 Areas of particular aesthetic or scientific value (e.g. archaeological sites) Yes No 

7 Areas or aspects of significance to Iwi Yes No 

If you have answered yes to any of the above, describe what effects your discharge may have and 

the steps you propose to take to avoid or mitigate these. 


4 Alternatives 

a) What alternative methods of disposal or discharge locations have you considered? 

• See project description of the detailed options assessment undertaken as apart of this project. 

Please the technical report appendix for 

b) Why did you choose the proposed method of disposal and location point? 


5 Maintenance and contingency 






a) How will the equipment controlling the discharge be operated and maintained to prevent equipment 

failure, and what measures will be implemented to ensure that the effects of any malfunction are 

remedied? 

• See project description in application for detail 

6 Monitoring 

a) What, if any, monitoring do you propose to carry out to ensure that the discharge does not have 


• See project description in application for detail 






State any contact made with neighbouring land owners and occupiers and organisations such as 

the Department of Conservation, Eastern Region Fish and Game Council, local Iwi and community 

groups. Where possible, record any comments made by these parties and outline your response to 

them. A list of people and organisations who you consider may be interested or affected should 

also be supplied wherever possible. 

Note: Environment Bay of Plenty can provide a form for the written approval of affected persons. 

See Application 






Form 9 

Discharge contaminants to land 

Question 7 















appropriate. 



1 Description of activity 

a) Where are discharged contaminants sourced from? (Tick as appropriate) 

Sewage treatment plant, servicing 

Piggery 

Industrial premises, (specify type) 

Water treatment 

Other (specify) State Highway 

If you ticked sewage treatment plant or industrial plant or industrial premises give description of 

type of process. 

2 Nature of the discharge and sensitivity of receiving environment 

a) Describe the contaminant: 

Temperature: See Application 

pH: 







Suspended Solids: 


BOD5: 


Faecal Coliforms: 


Enterococci: 


The chemical content, including heavy metals or toxic substances, nitrates, ammonia and 

dissolved reactive phosphorus: 


b) Is the contaminant treated in any way before discharge? 

Yes 

No 

If Yes, describe treatment 


c) What is the name of the water body into which the discharge is made (e.g. at the discharge site 

name of stream, river, lake, bay, harbour)? 


Is this in the coastal marine area? (See note 4 on application form) Yes No 

What is the water quality in the water body? 


How deep is the groundwater at the discharge site? 

What are the soil types at the discharge site? 


Rapid draining 

Free draining 

Good drainage 

Moderate drainage 

Moderate to slow drainage 

Any bore logs attached? 

Yes No 

Poor drainage 

Has the groundwater flow direction been determined? 

Yes 

No 






If Yes, what direction? See Application 

What are the ground contours like? (e.g. flat, moderate, steep, undulating, etc) 


Method of application: 

Contaminants to be discharged 

into land 

onto land 

How is the contaminant discharged? 


d) Discharge Rate Information: 

Maximum flow rate: 

Maximum daily flow: 

Average dry weather flow: 

Average wet weather flow: 





Is the discharge: continuous or intermittent 

What will be the maximum discharging period? 


e) Does the discharge also involve: 

diversion of natural water 

Yes 

No 

discharge to air 

Yes 

No 

piping across a waterway or water body 

Yes 

No 

If you answered Yes to any of the above, a separate consent application may be required. 

3 Assessment of effects on the environment 






Where your discharge could have a significant adverse effect on the environment a more detailed 



a) Comment on the possible effect the discharge may have on the quality of the receiving 

environment and users: 


b) Within a reasonable distance downstream, down groundwater gradient or in the vicinity of the 

discharge are there any: 

1 Obvious signs of biota (e.g. fish, eels, insect life, aquatic plants) Yes No 

2 Areas where food is gathered Yes No 

3 Water abstractions Yes No 



6 Areas of particular aesthetic or scientific value (e.g. archaeological sites) Yes No 

7 Areas or aspects of significance to Iwi Yes No 

8 Shallow groundwater Yes No 

9 Springs Yes No 

If you have answered yes to any of the above, describe what effects your discharge may have and 

the steps you propose to take to avoid or mitigate these. 


4 Alternatives 

a) What alternative methods of disposal or discharge locations have you considered? 


b) Why did you choose the proposed method of disposal and location point? 


5 Maintenance and contingency 

How will the equipment controlling the discharge be operated and maintained to prevent equipment 

failure, and what measures will be implemented to ensure that the effects of any malfunction are 

remedied? 







6 Monitoring 

What, if any, monitoring do you propose to carry out to ensure that the discharge does not have 















Environment Bay of Plenty 

PO Box 364 

Whakatane 

File ref. 

SEEN 

SEEN 

Free Phone: 0800 ENV BOP 

(0800 368 267) 

Free Fax: 0800 ENV FAX 

(0800 368 329) 

Website: envbop.govt.nz 

Office Use Only 

Application to Change or Cancel Condition(s) of Consent 

Resource Management Act 1991 (s.127) 

See notes to applicant (last pages of form) before 

proceeding with application form 

Pursuant to section 127 of the Resource Management Act 1991, the undersigned hereby makes 

application to change or cancel condition(s) of a resource consent other than any condition relating to 

the duration of the consent, and understands that section 88 to 121 apply with all necessary 

modifications. 

1 Full name of consent holder: 

(person(s) to whom the resource consent is issued) 

Company Name: 

Contact Person: 

Postal Address: 


Graeme Jelley 

91 Willow Street, Private Bag 

12022, Tauranga 3110, NZ 

Business phone: 07 577 7000 

Facsimile number: 07 571 8917 

Email: 

graeme.jelley@tauranga.govt.nz 






Environmental Planning 

Application Form 

For all application types (except Temporary Events) 

Site Location 

Planner check 


Street Address : SH 2 – Approximately Te Maunga to Domain Rd 

Suburb : Papamoa 

Legal Description : See Appendix 14 

Applicant Details 


91 Willow Street 

Private Bag 12-022 Tauranga 

Phone 07 577 7000 

Fax 07 577 7034 

Website 

www.tauranga.govt.nz 

GST No. 51-938-283 

Applicant Name : Kevin Reid, New Zealand Transport Agency 

Address of Applicant : See below 

Property Owner : See application for details Occupant (if applicable) : 

Address for Service 


Agent Name : New Zealand Transport 

Agency 


Postal Address : 

PO Box 430, Seventh 

Avenue, Tauranga 3140, 

NZ 

91 Willow Street, Private 

Bag 12022, Tauranga 

3110, NZ 

e-mail Address : kevin.reid@nzta.govt.nz graeme.jelley@tauranga 

.govt.nz 

Phone & Fax No’s : 07 9276009 07 577 7000 

07 578 2909 07 571 8917 

Type of Application/s (tick relevant boxes) 







4. Activity Status 

This project is complex and seeks to address issues related to flooding and stormwater in the 

Papamoa/Mangatawa area. As such, to assign responsibility for each activity that is required by this proposal 

we have outlined the consents required as part of this project and the agency responsible for that consent. 

The duration shown in the table refers to the suggested duration of the consent and reflects the temporary 

predominantly construction related activities versus the long term operational activities. 

The consents required are shown in the Table 1 and for the purposes of this application the table describes the 

activities to be undertaken generally from East to West as the catchment flows. 

4.1 Regional Water and Land Plan 

The consents required under the operative Regional Water and Land Plan are shown in the table below. 

Table 1: Regional Consents required and ownership status of each consent 

NOTE: All plan references made in this table refer to Plan 3932036-CK301 Rev C attached as Appendix 1. 

Mangatawa Flood Bypass and TEM Stormwater 

Consent Required Status Activity Plan 

Ref 

Proposed 

Consent Holder 

10yrs 

35yrs 

Regional Consents Required 

Land and Soil Disturbance Activities – Rule 1C, Form 2 

Earthworks Discretionary Construction of an earth bund @ 

Top Spill & Barrier @ Bruce Road 

2,4, NZTA 

Land and soil 

disturbance by 

vegetation clearing 

Restricted 

Discretionary 

Mangatawa Drain works - 

Vegetation Clearance 

3 NZTA 

Earthworks Discretionary Mangatawa Drain works – 

Installation of flood protection 

structures at Rail Bridge 

Earthworks Discretionary Mangatawa Drain works - Flood 

storage east of Kairua Road 

Earthworks Discretionary Drain widening between Bruce 

Road and Maranui Swale for flood 

protection. 

5, 6 NZTA 

1 NZTA 

NZTA 

Earthworks Discretionary Mangatawa Drain works - 10 NZTA 








Ref 

Proposed 


10yrs 

35yrs 

Construction of bund and flood 

storage area (Flood Bypass) on 

lower Mangatawa Drain 

Earthworks Discretionary NZTA component of TCC 

Treatment Pond Enlargement 

Discharges to Water and Land – Rule 48, Form 8, Form 9, Variation 

17A 

NZTA 

Discharges to Water or 

Land 

Discretionary 

Discharge (spill) from Mangatawa 

Drain across SH 2 to Land (in flood 

event) 

TCC 

Discharges to Water or 

Land 

Discretionary 

Discharge from Maranui Swale to 

harbour via culverts at Ch 6850 

into Mangatawa Drain (in flood 

event) 

9 TCC 

Discharge of Stormwater 

to Water or Land 

Restricted 

Discretionary 

Discharge from TCC Treatment 

Pond to harbour 

14 TCC 

Damming and Diversion of Water – Rule 48 

Diversion of water 

(Surface Runoff) 

Discretionary Operation of a Bund & Barrier in 2 

locations 

2,4 TCC 

Diversion of water 

(Surface Runoff) 

Discretionary 

Through 2 culverts at Mangatawa 

Lane (Ch 6850) 

9 TCC 

(in flood event) 

Activities in the beds of rivers streams and lakes – Rule 68, 71, Form 1 

Activity in the Bed Discretionary Mangatawa drain works (potential 

for temporary bed disturbance) 

Activity in the Bed Discretionary Mangatawa Drain widening to 

increase capacity (Ch 9000-9400 

east of Kairua Road) 

Activity in the Bed Discretionary Mangatawa Drain realignment at 

railway (includes erosion 

protection, gabion baskets) 

3 NZTA TCC 

1 NZTA TCC 

5, 6 NZTA 

Placing Culverts –Rules 59 to 59D, Form 1 

Culverts 

Restricted 

Discretionary 

Installation of culverts at Ch 6850 

from Maranui Swale to Mangatawa 

Drain 

9 NZTA 

Culvert Extensions 

Restricted 

Discretionary 

Extension of culverts under Kairua 

Road 

11 NZTA 

Culvert Permitted Install an 1800 dia culvert at 

Ch 5900 on MPBI land in an open 

12 TCC 








Ref 

Proposed 


10yrs 

35yrs 

drain 

Culvert Permitted Install a 1200 dia culvert at 

Ch 5900 on MPBI land in an open 

drain 

Modification to Culvert Permitted Ch 5700 upgrading of TCC culvert 

size from 750 to 1200 dia 

Modification to Culvert Permitted Install typical 450 dia culverts 

across SH2 between Ch 5250 and 

Ch 10850 

12 NZTA 

15 TCC 

16 NZTA 

* DOG = Deed of Grant – Required to undertake works on Ontrack Land 

4.2 Regional Coastal Plan - Variation of Consent 

The TCC application seeks a coastal permit for the increase in volume discharging to the harbour from the 

lower Mangatawa Drain and for an increase in discharge from an already consented discharge from the 

stormwater treatment wetland. 

An outlet runs into the Special Ecological Site 13 (SES) 3 and fresh water drains into the Coastal Marine Area 

(CMA). Rock weirs and earth bunds have been designed to contain the stormwater to the outlet channel 

however storm water will enter the SES. This outlet currently has a resource consent for discharge and this 

application seeks vary the conditions in this consent. 

Note, the current and the proposed future Maranui stormwater outlet both have a rock weir at the point of 

discharge to SES area, then the water flows through the SES area to the harbour, although most of the SES area 

is tidal so is potentially part of the harbour. 

There are no rules pertaining to stormwater discharge into an ecological area, however rule 9.2.4(a) of the 

Regional Coastal Plan applies. The discharge into the CMA is discretionary activity subject to the conditions 

set out in the existing consent. This application seeks to increase the volume and flow rate of this discharge. 

3 See Appendix 2 For location of SES 13 






Table 2: Regional Coastal Environmental Plan Consents Required and Ownership Status of each Consent 

TCC and TEM Stormwater Treatment Wetland 

Consent Required Status Activity 

Variation to existing Regional Coastal Consent RC 60061 

Plan 

Ref 

Proposed 


10yrs 35yrs 

Variation to discharge 

into the CMA 

Variation 

Increase in the volume of 

discharge from Tauranga City 

Council treatment wetland, RC 

60061. 

TCC 

From 3.9 Cubic metres a second, 

except when the 24 hour duration 

1 in 5 year return storm event is 

exceeded, to 13.4 cubic metres a 

second 

Discharges into the CMA Discretionary Discharge from lower Mangatawa 

drain to harbour. 

9 TCC 

4.3 District Plan Activity Status 

The proposed enlargement to the stormwater treatment wetland is located immediately north (outside) of 

Special Ecological Site 13s described in Table 3. The proposed works are outside the SES area and as such the 

rules apply to activities within or adjacent to the SES. 

Table 3: TCC District Plan General Natural Resource Rules - Maintaining Biodiversity and Protecting 

Ecosystems 

Appendix 14A: Special Ecological Site Register 

Map 

No. 

Eco. 

Site 

ID 

General Description 

ES13 12 Head of Rangataua Bay, northwest 

of sewage treatment plant 

Natural Heritage Values 

Estuarine wetland with transition 

vegetation sequence of mangroves 

through freshwater wetland. 

Habitat of banded rail and North 

Island fernbird, habitat of high quality. 

Significant amounts of earthworks and vegetation removal are required as part of the proposal. These activities 

are non complying activities subject to Rule 14.1 (b) and (c) which state: 






(b) Notwithstanding any rule to the contrary in the Plan, any activity that involves the removal, 

deposition, movement or disturbance in any 12- month period from within or adjacent to any Special 

Ecological Site of more than 10m³ earth/soil is a non-complying activity. 

(c) Notwithstanding any rule to the contrary in the Plan, any activity that involves the removal or loss in 

any 12-month period from within or adjacent to any Special Ecological Site of more than 20m² of 

indigenous vegetation is a non-complying activity. 

Chapter 24: Transportation Activity and Other Network Utility Rules 

Stormwater detention ponds and associated earthworks and structures under Table 24-1 in the Industrial 

Business Zone are controlled activities. The matters council reserves its control over include: 

24.3.2.1 

(a) District-wide rules contained within the Plan (see Chapters 11 to 18) 

(b) Imposition of financial contributions in accordance with Chapter 26 Financial Contribution Rules 

(c) Imposition of conditions in accordance with Section 108 of the Resource Management Act 1991. 

Table 4: District Consents Required 

Stormwater Treatment Wetland 

Consent Required Status Activity 

District Consents Required 

Land Use - Network 

Utility Rules 

Earthworks 

Vegetation Clearance 

Controlled 

Non 

Complying 

Non 

Complying 

Stormwater detention ponds and 

associated earthworks and 

structures under Table 24-1 in the 

Industrial Business Zone are 

controlled activities 

Construction of the Stormwater 

Wetland adjacent to an SES 

Vegetation removal for the 

Stormwater Wetland adjacent to an 

SES 






5. Site Description 

The purpose of this report is to assess the effects of a proposed stormwater management system for the TEM 

and the management of flooding across the highway. 

5.1 The Locality 

The catchment area relevant to the project includes the Mangatawa, Wairakei and Maranui catchments as 

shown in Appendix 3 as drawing 3932036–CK119 Rev F. The water generally flows from the Mangatawa 

catchment into the harbour, or in spill situations into the Maranui and Wairakei Catchments. As shown on 

drawings 3932036-ck073 to 3932036-CK075 (shown in Appendix 4), the area that works will be undertaken 

is approximately from chainage 5250 to 10800. 

Figure 2: Approximate Location of Proposed Works 

Project 

Area 






5.2 Land Use 

The subject area is located at Te Maunga within the Papamoa West Urban Coastal area. The site is 

approximately 5 kilometres in length, starting east of the Te Maunga intersection at Bay Park Stadium, and 

finishing near the Domain Road roundabout. The existing carriageway varies between 2 and 3 lanes with a 

100kph speed limit. Inland and to the south west of the State highway the East Coast Main Trunk Railway line 

runs parallel to the road. 

To the north of SH2 between chainage 5250 and 8300 there is predominantly residential subdivisions then 

followed by rural farmland to chainage 10800. On the southern side of the road the land is rural farmland 

separated by the State highway and East Coast Main Trunk railway (ECMT). 

There is an industrial development proposed by Mangatawa Papamoa Blocks Incorporated (MPBI) on the 

southern side of the State highway at approximate chainage 5700 to 6850. 

Papamoa has increased in population by over 600% since 1981. This rapid urban, residential commercial, light 

industrial and educational development has highlighted stormwater and flooding problems in the area for the 

new residential developments. 

5.3 Zoning 

The proposed site is within the jurisdiction of Tauranga City Council. The road itself is designated for a future 

four lane State Highway (part of TEM). 

The area to the north of SH2 is zoned Residential A from Te Maunga to approximately Bruce Road and then 

Rural to the Domain Road intersection. To the south from Te Maunga, the land is zoned Industrial Business and 

then Rural from approximately Mangatawa Lane. 

In the proposed project site there are several features of note from the District Plan: 

• The Maranui swale is designated as C116 shown with an underlying Residential A zone. However it is 

shown on the District planning maps as Green Belt zone. 

• The Special Ecological Site 13 is adjacent to proposed works about the existing TCC stormwater treatment 

wetland (shown in Appendix 4) 

• The Flood Hazard Policy Area covers much of the land south of the alignment. 

The increased discharge from the TCC stormwater treatment pond will discharge to the Coastal Marine Area 

which is administered by the Regional Council. The area is also noted as an Area of Significant Conservation 

Value for Banded rail, Pukeko, New Zealand kingfisher, White-faced heron and notated in the Regional Coastal 

plan as SSCMA-28. 






5.4 State Highway 2 

State highway 2 provides a strategic link with Rotorua and the farming, horticulture and forestry industry with 

the Port of Tauranga. It is also a section of the Pacific Coast Highway, a popular scenic route for travellers, 

campervans, caravans and holidaymakers. The link to the Port of Tauranga affects the types of vehicles which 

frequently use this stretch of road including heavy vehicles, tractors, sprayers and vehicles associated with 

these industries. 

State Highway 2 is also a utility corridor carrying water, sewerage, electricity, Telecom and high voltage 

cabling. These utility providers have been engaged as part of the TEM resource consent process (see 

application for details) and ongoing talks with these utility providers are taking place to identify opportunities 

to upgrade, maintain or relocate this infrastructure. 

5.5 Social Environment 

This area has attracted many residents seeking an urban coastal lifestyle and this has driven the demand for 

residential development to the north. By contrast however many of landowners adjacent to the eastern end of 

the site are/were farmers who have lived in the area for many years and they still place a large importance on 

rural amenity. It is this rural land that floods during high rainfall events and there is recognition from these 

landowners that this will happen. 

There is a general understanding amongst landowners that the trends in development in the Tauranga City and 

Papamoa areas create growth pressures. This has resulted in their land being required increasingly by 

infrastructure providers experienced by landowners as a result of infrastructure requirements. This being said 

most landowners consulted did not object to the motorway project but wanted to understand the details of the 

project (in most cases stormwater) and to be comfortable with the outcomes proposed. 

5.6 Cultural 

The iwi and hapu have an acute interest in the area because of historical and cultural associations. 

For this application NZTA has consulted with Ngaiterangi, Nga Potiki and Ngati Pukenga, Ngati He and Ngai 

Tukairangi about effects of this proposal. The outcome of this consultation is provided in Section 7. 

The Nga Potiki, Tamapahore Marae is situated on an elevated land overlooking the State highway to the South 

East of Te Maunga. This is one of the few sites that overlook the proposed roading development. Land to the 

west of the Marae is Maori land title owned by Mangatawa Papamoa Block Incorporated. 

Tauranga Harbour is known to tangata whenua as Te Awanui. Te Awanui is the rohe moana of three iwi - Ngāti 

Ranginui, Ngāiterangi, Ngāti Pūkenga. Most of the marae of these iwi are located close to the harbour margins. 

The mauri of the harbour is extremely important for the customary relationship tangata whenua have with the 

harbour, in particular customary food gathering. 






5.7 Archaeological 

An archaeological assessment was undertaken during the TEM resource consent phase of the project for the 

road alignment in this location. An additional assessment was undertaken to include all the works proposed in 

this document and the results are summarised below. This area includes the proposed works in the stormwater 

treatment wetland for MPBI and the Tauranga City Council proposed upgrade to the Maranui swale. These 

assessments are attached as reports in Appendix 6. 

5.7.1 Summary of Results 

There are seven recorded archaeological sites within 300m of the proposed construction corridor. None of the 

seven sites falls within the affected properties; however, there remains a possibility that unrecorded 

subsurface archaeological sites are present within the affected areas which may be disturbed by ground 

disturbance associated with the construction of the Tauranga Eastern Motorway. There are no previously 

recorded archaeological sites and no unrecorded archaeological sites were within land affected by this 

proposal. However Pre-European occupation on the eastern edge of the wetland and on raised ground on the 

eastern side of Mangatawa Lane was likely to have been extensive. The area was a poorly drained wetland and 

would have been a source of construction materials such as raupo and food such as birds and eels. The 

collection of such resources rarely leaves an archaeological record, however, swamp and wetland environments 

often contain artefacts made form organic materials such as wood and flax as the anaerobic conditions of 

wetlands provide an environment that can preserve buried organic materials that rarely survive elsewhere. 

Many wooden and organic artefact assemblages have been recovered from wetland sites throughout the Bay of 

Plenty. Wetland areas within the construction corridor and the proposed works to construct the Flood Bypass 

have the potential to contain such artefacts especially given the high concentration of archaeological sites on 

the surrounding hill country and dune plain. 

5.7.2 Archaeological Significance 

This part of the Bay of Plenty is rich in archaeological evidence of Maori occupation, the majority of recorded 

archaeological sites relating to the period before the arrival of Europeans. The recorded sites may be 

significant individually because of the archaeological information they contain relating to the history of Maori 

occupation in the area, but they also gain significance as components in a wider archaeological landscape. The 

nature and sequence of occupation over time is best understood with reference to the full range of sites within 

the area and the relationship between them. 

Any subsurface archaeological sites that may be present within the construction corridor may have the 

potential to add to our understanding of the nature and antiquity of the surrounding pre European Maori 

cultural landscape. 

5.7.3 General Considerations 

The archaeological assessment undertaken considers archaeological values and does not include an 

assessment of Maori values. Such assessments can only be made by the tangata whenua. It should be noted 

that archaeological survey techniques (based on visual inspection and minor sub-surface testing) cannot 

necessarily identify all sub-surface archaeological features, or detect waahi tapu and other sites of traditional 

significance to Maori, especially where these have no physical remains. 






5.8 Topography 

The Papamoa Hills area is the dominating feature in this catchment and falls in a northerly direction to the 

ECMT across rolling rural farmland. Once at the ECMT the topography is generally flat and low-lying as this 

area was once Papamoa swamp land that was shaped by the former course of the Wairakei Stream. 

Travelling westwards from Domain Road along SH2 the topography is low-lying as described above, although 

there is a series of ridges that the ECMT and SH2 cross. From Mangatawa Lane the land to the south is flat and 

low lying out to Rangataua Bay in the Tauranga Harbour. 

5.9 Geology 

From the existing Te Maunga roundabout to Mangatawa Lane the route is essentially underlain by Foredune 

Sand and Alluvium, with the Fluvial Terrace at depth. The thickness of the Foredune Sand varies depending on 

the position of its south western boundary in relation to the route alignment. The base of the alluvium is not 

anticipated to vary significantly. 

From Mangatawa Lane to east of Parton Road the route is underlain by varying thicknesses of Peat, Alluvium 

and Fluvial Terrace. The ridges of Fluvial Terrace and intervening low lands reflect a historical topographical 

surface formed of the Fluvial Terrace. The low lands having been subsequently in-filled, firstly with Alluvium 

and more recently with Peat. 

5.10 Ground Conditions 

Geotechnical investigations were undertaken in 2006/07 for the TEM. One key issue of significance to this 

project relates to the significant depth, low strength and high compressibility of the recent peat and alluvial 

sediments and how these ground conditions affect the stability and settlement of the earthworks for the 

stormwater treatment pond. 

Other areas that have required consideration included the volcanic soils that underlie parts of the route, the 

high groundwater level and the significant depth of loose or soft sediments which the structures will be 

founded over. 

5.11 Contaminated Land 

To date the desktop assessment has shown there is no significant contaminated ground material at this 

location. However, the limited information known regarding the current and historic land uses along the TEM 

corridor suggest that soil contamination cannot be precluded and field investigations to assess the likelihood 

of encountering contaminated land will be undertaken before construction. Potentially contaminative activities 

that may have been undertaken within the scheme corridor could include the following (possible associated 

contaminants shown in brackets): 






• Farmland (e.g. sheep dips that may have used persistent chemicals containing arsenic, dieldrin, aldrin and 

lindane and DDT; offal pits; farm tips etc); 

• Horticultural land (persistent chemicals used in pesticides/herbicides such as DDT); 

• Railway land (e.g. hydrocarbons); 

• Flood plains (e.g. contaminants associated with runoff from land); and 

• Areas of unknown fill (e.g. contaminants vary according to the source of the fill material). 

Further to these activities, where stormwater is currently collected within grass swales and drainage channels, 

it is likely that the build up of contaminants in the soils within these areas has occurred. 

Investigations will need to be undertaken with the aim of enabling the potential risks associated with any 

contamination (if found to be present) to be assessed such that appropriate management mechanisms can be 

defined and implemented. A programme of land use review and intrusive site investigating is programmed to 

take place before construction commences in order to characterise site contamination. 

5.12 Land Drainage 

Much of the route is low-lying and serviced by land drainage works. In the Te Maunga area drainage is 

currently through soakage or the TCC piped system. A major drain, the Mangatawa drain, flows east to west 

between the current SH2 and East Coast Main Trunk (ECMT) railway, draining the existing SH2 and the 

Papamoa Hills catchment to the south. This discharges to the Harbour at Rangataua Bay. This drain has 

insufficient capacity, and in large floods it spills north across SH2 into the Papamoa urban area. 

5.12.1 Catchments 

There are three distinct catchments important to this proposal along this section of motorway up to Domain 

Road. The principal ones are Mangatawa (south of the TEM), Maranui and Wairakei north of the TEM, in the 

west and east respectively). These catchments are shown on the plan 3932036-ck119 in Appendix 3. 

a. Maranui Catchment 

The Maranui Catchment contains a mix of residential and rural land and the flow path for this catchment is 

through the Maranui swale through the Stormwater Treatment Wetland to Rangataua Bay. Perhaps the most 

significant aspect of the catchment is its large areas of undeveloped residentially zoned land. The implications 

are important for stormwater generation and runoff. 






b. Wairakei Catchment 

The Wairakei Catchment covers most of Papamoa and is a sensitive catchment to stormwater runoff. It is 

covered by a comprehensive consent that this application has taken account of. 

The Wairakei comprehensive stormwater management consent has included in its calculations an expected 

spill over from the Mangatawa catchment as part of the conditions of consent for the 48 hour 50 ARI storm 

event. 

c. Mangatawa Catchment 

The Papamoa hills area is the major catchment contributing to the Mangatawa Drain. The southern part of the 

catchment flows directly into the drain and thence without treatment into the harbour, at Rangataua Bay. The 

current SH2 runoff in this catchment is partly to the Mangatawa drain, and partly to the Maranui swale. For the 

proposed TEM this will change, with both the southern and northern carriageway draining into the Maranui 

swale and being treated in the Maranui Pond. 

5.12.2 Catchment Hydrology 

The Mangatawa Drain is about 2,500m long where it is alongside the proposed Tauranga Eastern Motorway 

(TEM). The drain has a vegetated, earth lined channel that is tightly constrained between the railway (to the 

south) and the motorway (to the north). There is some uncertainty as to who is responsible for its 

maintenance, although in the past Tauranga City Council has undertaken maintenance. It is generally located 

on either road reserve or railway land. 

In larger flood events excess flow spills north across the motorway at two locations, and into the Papamoa 

urban area. The two locations are identified in this report as “Top Spill” and “Bruce Road Spill” (although the 

spill covers several hundred metres of highway in the general vicinity of Bruce Road). 

While the discharge can be volumetrically large, it is generally spread as a shallow overflow (a few hundred 

millimetres deep) or ponding across several hundred metres length of highway, and has resulted in highway 

closure in the past. The most recent closure was in May 2005, and lasted for 14 to 18 hours. The frequency of 

spills appears to be about 5 yearly on average at present. TCC has updated their design rainfall figures and 

these have been applied to this investigation and modelling. These design rainfall figures are based on 

predicted climate changes to 2055. With the climate adjusted rainfall figures the frequency of spills is 

predicted to increase to about 3 yearly. 

In addition to closing the motorway, the spills discharge into developing urban areas on the northern side of 

the motorway, with potential consequences for TCC for flood risk management. 

The Top Spill discharge flows to the Wairakei Stream, where there is significant existing urban development, 

plus plans for growth. This stream predominantly relies on ground soakage, with additional discharge to 

Harrisons Cut and the Grant Place discharge, so is sensitive to additional flood flow volumes. The Bruce Road 

Spill discharges to TCC’s Maranui Swale (across private land), and conveys urban stormwater along the 

northern side of the highway. It then travels under the highway and the railway to the wetland treatment 

ponds, before discharge to the Tauranga Harbour at Rangataua Bay. The swale was originally designed without 






accounting for climate change, or for the effects of the Mangatawa Spill, and therefore will need significant 

upgrading to meet maximum flood level standards in the urban area. 

5.13 Ecology 

5.13.1 Mangatawa Drain 

The Mangatawa drain flows within a well-defined channel, northwest along the southern side of State Highway 

two (SH2). The drain veers southwest past Mangatawa Lane and discharges to Rangataua Bay. The channel is 

predominantly shaded by the steep banks as the riparian vegetation is minimal, generally consisting of rank 

grasses and weeds, and the occasional tree. 

One site was sampled (April 2008) within the upper Mangatawa drain between Mangatawa and Domain Road 

(Site 5; E: 2798350 N: 6383240). At this site various components of the aquatic ecosystem were sampled and 

sediment and water quality samples were collected for laboratory analysis. 

At the time of sampling the drain had formed ponded habitats at both ends of the culvert beneath Kairua 

Road, and some of the bank vegetation had been cleared as a result of recent instream works. 

a) Sediment Quality 

Sediment quality data were compared with the ANZECC (2000) guidelines for the common metals, copper, lead 

and zinc. Levels recorded in the upper Mangatawa drain at Site C fell below the lower Interim Sediment Quality 

Guidelines (ISQG) for metals, indicating that the likelihood of adverse effects on instream organisms would be 

low. 

Hydrocarbon levels within the upper Mangatawa drain were also below the laboratory detection limit, however 

no guidelines exist for hydrocarbons for the protection of aquatic life. 

b) Water Quality 

Overall, the upper Mangatawa drain at Site 5 had good water quality as determined by spot measurements, 

with the water being cool (16oC), having high levels of dissolved oxygen (8mg/L & 81%) and moderate 

conductivity (107 μS/cm), however clarity was poor (0.2m) (Table 5). 






Table 5: Rangataua Bay Catchment Sediment Quality Results 

Laboratory measurements of surface waters for common metals, nutrients and bacteria, indicated elevated 

concentrations of the bacterium Escherichia coli (2400 NPM/100ml) suggesting faecal contamination of the 

upper Mangatawa drain. As the drain receives flows from agricultural land, it is likely that farm runoff has 

contributed to these elevated concentrations. No guidelines exist for bacteria in relation to aquatic life; 

however such a concentration is in excess of the guideline levels for contact recreation in freshwaters (MfE, 

2002). It is accepted that this waterway is unlikely to be used for contact recreation. 

c) Aquatic Fauna 

Aquatic fauna (macro invertebrates & fish) within Mangatawa drain at Site 5 were limited, and no rare or 

threatened species were recorded. The macroinvertebrate community had low diversity (11 taxa) and was 

dominated by the common freshwater snail (Potamopyrgus antipodarum), which is tolerant of degraded habitat 

quality. One taxa from the generally sensitive EPT group (Ephemeroptera,Plecoptera,Trichoptera), of insects 

was recorded, namely the caddisfly larvae Triplectides obsolete (Trichoptera). This species is not considered to 

be especially sensitive to nutrient or organic enrichment. The Macroinvertebrate Community Index (MCI) score 

was 58 and indicative of ‘poor’ instream conditions (Stark & Maxted, 2004). 

In terms of fish, only two native species, namely inanga (Galaxias maculatus) and common bully 

(Gobiomorphus cotidianus) were recorded in low numbers (total n = 4). While only a low diversity of fish was 

recorded within the upper Mangatawa drain (Site 5), a more diverse range of native fish (n = 7) has previously 

been recorded from an unnamed tributary draining the Papamoa Hills (Source New Zealand Freshwater Fish 

Database). This suggests that the Mangatawa drain is important as a migration route for native fish using the 

upper catchment. 

5.13.2 Maranui Swale 

The Maranui swale also flows within a well-defined channel, northwest along the northern side of SH2. The 

swale enters a culvert beneath SH2 and then flows southwest through an elongated pond (Stormwater 






Treatment Wetland) that has been extensively planted with native vegetation. The pond discharges to 

Rangataua Bay through an area that has been identified by Environment Bay of Plenty as having significant 

ecological value - Special Ecological Site - SES (Environment Bay of Plenty, 2003). 

5.13.3 Stormwater Treatment Wetland 

The stormwater treatment pond is sited within a rectangular block of almost level land between SH2 and the 

Rangataua Bay shoreline and sewage ponds. In its irregular outline this pond is an enlargement of a former 

natural depression. The pond is a specifically designed and constructed artificial pond developed by the 

Tauranga City Council. The water-level of the pond was about a metre below the ground surface at the time of 

the assessment. The depth of the pond is unknown. No sign of prolonged flooding up to the bank tops or 

beyond was apparent. 

The soil-forming substrate comprised mainly sand, but thin layers and patches of peat were also present. No 

buried wood was seen in the pond’s banks or in the sides of the Maranui Drain. The remainder of this 

rectangular block is vegetated to its boundaries, as discussed below. 

a) Vegetation 

The water of the pond was dark brown-stained by the peat. No floating aquatics, such as duckweed (Lemna, 

etc) were recorded in the pond. A covering of parrot’s feather (Myriophyllum brasiliense) was evident for 1-2m 

out from the bank of the pond. A much smaller amount of Potamogeton suboblongus was present in places. 

The pond’s banks are a metre or so high. They are stable despite their sandy nature, and are mostly thickly 

vegetated. In places their cover is predominantly of jointed rush (Apodasmia similis) and searush (Juncus 

kraussii), along with a lesser amount of bachelor’s button (Cotula coronopifolia) and Triglochin striatum. In 

other places, perhaps particularly where flax (Phormium tenax) comes right to the upper edge of the bank, 

there are dense growths of pampas grass (Cortaderia selloana). (It appears that herbicide may be being used to 

control this weed). 

The remainder of the block is a managed cover, partly of mown grass paths and clearings and partly of a tall 

scrub dominated by cabbage trees (Cordyline australis). The largest cabbage trees (up to a dozen) reach 13 m 

or more tall and 1 m or more in basal diameter. The majority of these trees are multi-trunked. It appears that 

at least the largest individuals, (and possibly also several of the lesser stature ones), have persisted from a 

former situation as relics in pasture. (A few such veterans persist in the pasture adjoining to the east). Only a 

small amount of shrinkage of any underlying peat seems to have occurred around these trees. 

Under the broken upper layer of these 5-13 m tall cabbage trees there was a dense cover of native shrubs and 

small trees, particularly Coprosma repens and C. robusta, and numerous (very vigorous) bushes of flax and the 

surface of the ground was covered by leaf litter. 






The mown grass areas were generally dominated by tall fescue. On the seaward side of the cabbage tree scrub 

there was a large damp open area of this grass that contained a few cabbage trees and large clumps of 

pampas grass. The limited diversity of this scrub vegetation, and also the near absence of weeds such as 

Chinese privet and honeysuckle, indicate that (except for some of the larger cabbage trees) the vegetation that 

surrounds the pond is mostly a planted one. [The only historical information located was the topographical 

sheet NZMS 1 “Tauranga”, 3rd edn, 1965. This (Figure 2.1) shows the site (and beyond) as a rectangular block 

of scrub. Possibly however there was some subsequent clearance of all but the cabbage trees, before the pond 

was formed]. 

b) Avifauna 

The avifauna was assessed in a walkover of these areas and at various locations their avifaunal characteristics 

noted. Recorded calls were played of spotless crake, fernbird and banded rail using a Johnny Stewart MS512 

Wildlife Caller with an S2500 15 watt speaker and amplifier. Calls for spotless crake were played at several 

points beside the aquatic habitat of the Stormwater Treatment Wetland and the SES while; fernbird and banded 

rail calls were played within the rushmarsh and mangrove habitat of the SES. 

Species of birds observed utilising the site and their principal habitats are shown in Table 6. A total of 15 

species was recorded with the higher diversity applying to the stormwater treatment area as a result of its 

abundant and flowering flax together with cabbage trees and native shrubs. Of the fifteen species, six were 

native, one endemic and eight introduced. One species that is considered to be of conservation concern was 

recorded. North Island fernbird was present in the SES – it is rated as “sparse” (at risk) on a national basis. 

A total of 13 species was recorded in these areas, a diversity that may have been enhanced as a result of 

abundant flax flowers that were being utilised as a food source by several species. All the birds recorded in 

this area were common or abundant species as follows: 






Table 6: Species of Birds Observed utilising the wetland and their Principal Habitats 

c) Herpetofauna 

The availability of native reptile habitat was visually assessed within the stormwater treatment wetland on 28 

November 2008. The available habitat within the wetland was relatively open, with flax (Phormium tenax), 

Coprosma spp., pampas and rank grassland patchily abundant. These characteristics provide ideal habitat for 

terrestrial skinks, and some gecko species. Thirty sampling stations were laid throughout Te Maunga wetland 

on 26 November 2008, in areas most likely to provide lizard habitat (e.g. bush edges, alongside vegetation, 

log piles etc.). Sampling stations consisted of 5-clustered (n = 150) artificial refuges (ARs). ARs used in this 

survey were 500 mm x 500 mm corrugated Onduline© sheets (distributed by GBS Group Ltd). Onduline© is an 

organic, bitumen-saturated material used in reptile surveys throughout New Zealand, due to its light weight 

and suitable thermal properties (Lettink & Cree 2007, Wilson et. al 2007). ARs were placed out one month prior 

to inspection to allow time for colonisation by target species. All sampling stations were checked four times 

(9th, 20th, and 29th January, and 4th February) during the survey period. 

Site visits for AR checks were under warm (sunny or cloudy) conditions, between 10 am and 12:30 pm. 






A total of 22 Rainbow skinks were recorded from 12 sampling stations. Rainbow skinks were visually 

abundant. Six copper skinks were also recorded from five sampling stations at the SMA during the survey 

(Figure 3). 

Figure 3 Positions of Sampling Stations within the Stormwater Treatment Wetland Area 

Key: Yellow dots: No lizards present; Green dots: Rainbow skinks; Red dots: Copper skinks. 

d) Aquatic Fauna 

Aquatic fauna (macro invertebrates & fish) within the stormwater treatment wetland were limited to ten 

macroinvertebrate taxa and two native fish species; no rare or threatened species were recorded. The 

macroinvertebrate community was dominated by the common freshwater snail (Potamopyrgus antipodarum), 

which is tolerant of degraded habitat quality and no taxa from the generally sensitive EPT group of insects 

were recorded. The MCI score was 59 and indicative of ‘poor’ instream conditions (Stark & Maxted, 2004). 

5.13.4 Special Ecological Site - Salt-marsh and Mangrove (SES) 

The salt-marsh–mangrove SES area extends southwards from the southern boundary of the stormwater pond 

block out to the rubble causeway of the sewage treatment ponds, and also extends eastwards about 250 m to 

where the large Mangatawa Drain discharges into Rangataua Bay. This point is also where seawater enters the 

SES. 

The SES is very low-lying, except for slightly elevated ridges of spoil along the sides of old drains (which tend 

to run parallel to the original northwest-southwest grain of this landform). The intertidal surface is sandy 

towards the land, but muddy in the mangrove–dominated zone seawards. 






a) Vegetation 

The salt-marsh occupies the landward half of this area, and mangrove the seaward half. There is a distinct 

gradation in the salt-marsh vegetation: a landward community of sea-rush and open sandy areas with patches 

of glasswort (Sarcocornia quinqueflora) and Samolus repens gives way seawards to a marsh dominated by 

jointed rush. Salt-marsh ribbonwood (Plagianthus divaricatus) is conspicuous as an emergent towards the 

western end of the searush zone, as youthful-looking bushes of c.1-1.5 m tall. Salt-marsh ribbonwood and 

sea-rush are also common along the foot of the rubble berms that define the western and southern edges of 

most of the SES. Native species of much less cover in the SES include Cotula coronopifolia, Triglochin striatum, 

Selliera radicans, Isolepis cernua, I. nodosa, Lobelia anceps, Juncus pallidus and Baumea juncea. The mangrove 

canopy is a nearly continuous one, and increases slightly in height seawards, reaching c.1.5 m high along the 

tidal inlet just inside the shore-parallel bund of the sewage ponds. Judging by the considerable amount of 

lichen on their branches, conditions are less than ideal for mangroves. 

The SES seems to have no especially noteworthy botanical features and an increase in the amount of treated 

stormwater discharged through it seems likely to result only in changes to the zonation of the dominant 

species only. 

b) Avifauna 

The SES is Site No.13 in Owen (1993), which is the source reference for the Tauranga District Plan. One pair of 

banded rail plus a juvenile were observed in that survey (1990) with Pukeko, NZ kingfisher, mallard and whitefaced 

heron. No fernbirds were reported and the habitat quality was described as moderate – stock damage; 

rubbish tip leachates; rats and feral cats common. Banded rail (Gallirallus philippensis assimilis; moho-pereru) 

is also considered to be sparse (i.e. at risk) on a national basis. In this survey fernbird was recorded in marsh 

ribbonwood – searush – jointed rush habitat adjacent to the access-track from the stormwater management 

area and adjacent to the Vector Gas pipeline route. Fernbirds were both seen and heard on either side of the 

access track. 

Fernbird calls were also played throughout the rushmarsh habitat but no further birds were located. Accessible 

areas of silt and sand substrate were inspected for banded rail foot-prints and recorded calls were played 

throughout both the rushmarsh and mangrove – dominated habitat; no footprints were found and no calls 

elicited. 

In the 1990 survey (Owen, 1993) a pair of banded rail had been observed in this area and four individuals were 

recorded in similar habitat near the end of Tip Lane together with fernbirds. The combination of rushmarsh 

habitat abutting low, dense mangroves would provide good potential habitat and it would be unusual if banded 

rail did not utilise the area at least on an intermittent basis. 

Other birds observed using the habitat were harrier, NZ kingfisher, pukeko (common throughout), welcome 

swallow and white-faced heron. In addition, five pied stilt and two grey reed herons were observed feeding on 

the intertidal flats around the channel edges and two paradise shelduck were observed resting on exposed 

intertidal sand. 

Overall the rushmarsh – mangrove habitat is a high value area for marshbirds and is presently in an 

undisturbed condition – the wetland vegetation has recovered following installation of the gas pipeline, and 

farm stock has been excluded. 






c) Herpetofauna 

The availability of native reptile habitat was visually assessed within the Special Ecological Site 13 (SES, 

Tauranga District Plan) on 28 November 2008. The SES consisted of saltmarsh and mangrove, and was 

considered unsuitable for native lizards. 

d) Water Quality 

The water quality being discharged from the stormwater treatment wetland through the special ecological site 

was generally characterised by elevated levels of some nutrients and bacteria. Elevated concentrations of the 

total nitrogen, nitrate and total phosphorus were recorded downstream of the stormwater treatment wetland, 

within the special ecological site (Site W1a), and were in excess of the ANZECC (2000) upper guideline limits. 

As the inorganic nitrogen and phosphorus species tested were below the relevant guidelines levels, with the 

exception of nitrate, it is likely that the majority of nutrients present in the system are in an organic form, and 

are therefore less readily assimilated by macrophytes. 

High bacterial counts recorded at the outlet from the stormwater treatment wetland (Site W1a) were in excess 

of the guideline levels for contact recreation in freshwaters (MfE, 2002). No specific guidelines have been 

established for bacteria in relation to the protection of aquatic life and it is accepted that this waterway is 

unlikely to be used for contact recreation. 

The number of Escherichia coli at the outlet from the stormwater treatment wetland (Site W1a) exceeded the 

lower MfE (2002) guideline, which indicates faecal contamination. Farm runoff is one possible source of 

contamination within these waterways, given the historical farming landuse of the area surrounding Maranui. 

Table 7: Sampling Site Locations 






e) Aquatic Fauna 

Aquatic fauna (macroinvertebrates & fish) within the special ecological site were limited to seven 

macroinvertebrate taxa, four native fish and one introduced fish. No rare or threatened species were recorded. 

The macroinvertebrate community was dominated by the common freshwater snail (Potamopyrgus 

antipodarum) and the estuarine amphipod (Melita awa), which are considered tolerant of degraded habitat 

quality. No taxa from the generally sensitive EPT group of insects were recorded. The MCI score was 88 and 

indicative of ‘fair’ instream conditions (Stark & Maxted, 2004). 

5.13.5 Rangataua Bay 

Rangataua Bay, located in the upper southern arm of Tauranga Harbour, receives stormwater from the 

stormwater management area (treatment pond) and the Mangatawa drain. The sediments at the mouth of the 

Mangatawa drain are relatively coarse grained sands with a small component of silts and clays. 

The intertidal flats supported a sparse population low mangrove plants, the pneumatophores of which 

supported the barnacle Chaemosipho columna . A sparse population of burrowing mudcrabs (Helice crassa) 

and occasional mudsnails (Amphibola crenata), turret shell (Zeacumantus lutulentus), topshell (Diloma sp) and 

whelks (Cominella sp.) were recorded in the coarse sands. Burrows in the sand indicated the presence of 

populations of estuarine worms and amphipods, however, no populations of edible shellfish such as cockles or 

pipis were found in this area of the Bay. Several small patches of the alga Ulva luctuca were observed on the 

intertidal sands. Four sediment quality samples were collected and were analysed for metallic, persistent 

organic and nutrient concentrations. The results of these analyses are presented as Table 8. 

Table 8: Results of Rangataua Bay Sediment Quality Analyses 

A suite of metals and metalloids were analysed for in the Rangataua Bay sediments and all of these parameters 

were detected in low concentrations in the sediments, well below the respective ANZECC interim sediment 

quality guidelines. 






Concentrations of total nitrogen and total phosphorus were analysed in each of the sediment samples collected 

from Rangataua Bay. Total nitrogen concentrations were somewhat variable with a slightly elevated 

concentration recorded from Site 2 in the main channel as the Mangatawa Drain discharged across the 

intertidal flats. The total phosphorus concentrations in the sediment samples suggest an attenuation effect 

with a reducing concentration of total phosphorus with an increasing distance from the Mangatawa Drain 

across the intertidal flats of Rangataua Bay. Together these nutrient results suggest that the Mangatawa Drain 

may provide slightly elevated concentrations of total nitrogen and phosphorus to Rangataua Bay, however, the 

variation in concentration is not high and these results are not indicative of serious nutrient input to the upper 

reaches of Tauranga Harbour. No sediment quality guidelines for total nitrogen or phosphorus are listed in the 

ANZECC guidelines. A wide range of haloethers, nitrogenous organic compounds, organochlorine pesticides, 

polycyclic aromatic hydrocarbons, phenols, plasticisers and other halogenated organic compounds were 

analysed for in the sediment quality samples. In none of the samples were any semi-volatile organic 

compounds found in concentrations above the minimum detection limit for the analytical methods used. 

The Mangatawa Drain, the stormwater management area and their respective catchments do not contribute 

significant quantities of metallic or persistent organic contaminants to the intertidal area of Rangataua Bay and 

the upper reaches of the Tauranga Harbour. There is some suggestion of slightly increased nutrient input into 

this part of the harbour, however, any such nutrient inputs are not currently significantly impacting upon the 

ecological function of either Rangataua Bay or the upper Tauranga Harbour. 

5.13.6 Conclusion 

The stormwater treatment wetland is of moderate significance but only on a local basis, as it contains a 

relatively large area of flax – cabbage tree – shrubland habitat, a type that does not appear to occur elsewhere 

in the Te Maunga to Mangatawa area. Nevertheless it only supports species that would also occur in other 

types of adjacent habitats around the upper part of Rangataua Bay. Calls of spotless crake (Porzana tabuensis 

plumbea; puweto) were played at four locations adjacent to the existing meanders but no response was 

elicited. The presence of crakes (sparse; at risk) is unlikely given the lack of any significant riparian rush, Carex 

or raupo fringe that would provide cover and nesting habitat. Most of the fringing aquatic vegetation consists 

of Myriophyllum only. 

In summary, the stormwater treatment wetland provides habitat that is of moderate value but only in a local 

context and no species of national conservation concern was recorded. The rushmarsh – mangrove habitat of 

SES No.13 is considered to have high ecological values in a regional context and contains fernbird, a species 

considered to be at risk nationally, while its use by a second at risk species, banded rail, is also likely. This 

area should be avoided by any major works associated with modification to the existing stormwater 

management area. 

The Mangatawa drain and Maranui waterway (swale, wetland and significant ecological site) are both typically 

open waterways, with cool to warm water and variable levels of dissolved oxygen, clarity and conductivity. The 

variable levels of conductivity are considered to reflect the presence of saline waters within the lower reaches 

of both the Mangatawa drain and the Maranui waterway. Elevated counts of E. coli bacteria were also recorded 

in both waterways and reflects the agricultural land use. While overall the water quality of the Mangatawa drain 

was reasonably good, with the water for the most part being cool and well oxygenated, although discoloured 

on occasions, that of the Maranui swale was poor, with low levels of dissolved oxygen and poor visual clarity 

(0.1m). 




Table 9: Summary of Ecological Characteristics 



Mangatawa Maranui Roadside 

Site 

5 

(upstream) 

1 1a 

(downstream) 

2 

(upstream) 

2a 2b 2c 

(downstream) 

3 

(side 

swale) 

4 

Survey date Apr ‘08 Apr ‘08 Oct ‘08 Apr ‘08 Oct ‘08 Oct ‘08 Oct ‘08 Apr ‘08 Apr ‘08 

Habitat 

Average width (m) 1.7 2.4 6.5 3.0 3.5 Pond 4.5 2.5 1.2 

Average depth (m) 0.25 0.24 0.2 0.22 0.20 - 0.25 0.23 0.16 

Dom. substrate type Sand Mud/Gravel Mud Mud Cobble - Mud/sand Mud Mud 

Aquatic Vegetation 

Glyceria 

Willow 

weed 

Curly 

Pondweed 

Glyceria 

Nitella 

Watercress 

Willow weed 

Glyceria 

Nitella 

Glyceria 

Ludwigia 

Parrots 

feather 

Pondweed 

Willow 

Weed 

Curly pondweed 

Ludwigia 

Oxygen weed 

Parrots feather 

Pond weed 

Starwort 

Curly 

pondweed 

Parrots 

feather 

Starwort 

Mangroves 

Ulva 

Ludwigia 

Pondweed 

Willow 

weed 

Duckweed 

Parrots 

feather 

Willow 

weed 

Water Quality 

Temperature ( o C) 16.0 14.6 19.1 13.8 20.9 20.8 21.3 15.3 16.7 

Oxygen saturation (%) 81 29 91 5 68 70 95 12 17 

Dissolved 

(mg/L) 

oxygen 

8.0 2.8 8.4 0.5 6.0 6.4 8.3 1.2 1.6 

Conductivity (μS/cm) 107 130 175 198 190 627 773 - 204 

Visual clarity (m) 0.2 0.8 0.5 0.1 0.4 0.5 0.4 0.2 0.1 


Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE



Mangatawa Maranui Roadside 

Site 

5 

(upstream) 

1 1a 

(downstream) 

2 

(upstream) 

2a 2b 2c 

(downstream) 

3 

(side 

swale) 

4 

Macro invertebrates 

No. of taxa 11 11 10 10 6 10 7 11 13 

Dominant taxa Snail Seed shrimp Snail Damselfly 

Chironomid 

midge larvae 

Snail 

Amphipod & 

Snail 

Damselfly 

Damselfly 

% EPT 15 33 - < 1 - - - 0 < 1 

MCI-sb 58 59 67 62 73* 59 88 58 64 

Fish 

No. of species 2 2 3 1 4 2 4 2 0 

No. of fish 4 3 24 1 - 16 15 3 - 

Species recorded 

Common 

bully 

Inanga 

Common 

bully 

Giant bully 

Eels 

Common 

bully 

Giant bully 

Gambusia 

Eels (a) 

Bullies (o) 

Inanga (o) 

Gambusia (c) 

Shortfin eel 

Common 

bully 

Shortfin eel 

Common 

bully 

Inanga (o) 

Gambusia (c) 

Gambusia 

Inanga 

- 


Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE



Both of these waterways provide habitat for a small range of native fish (Mangatawa: n = 4; Maranui: n = 3) 

and common macroinvertebrates. No rare or especially sensitive species were recorded. Previous records of 

native fish indicated that there are six diadromous (migrating between fresh and saltwater) species within the 

upper catchment of the Mangatawa drain, suggesting that the Mangatawa drain is important as a migration 

route. Longfin eel (Anguilla dieffenbachii) were recorded from a tributary draining the Papamoa Hills in 2001. 

This species is diadromous and is considered to be ‘in decline’ on a national basis (Hitchmough et al., 2007). 

All of the native species recorded within the Maranui waterway are also considered to be diadromous; however 

these species are considered ‘not threatened’ by the Department of Conservation (Hitchmough et al., 2007). 






6. Alternatives Considered 

An investigative process was developed to find possible solutions to manage the stormwater derived from the 

proposed TEM and to reduce the frequency of spills across the State Highway. The process is outlined in 

Section 8 Consultation. For the purposes of this report we refer to the activities related to the flooding issue 

as the Mangatawa Flood By-pass and the issues related to the TEM roadway are referred to as the TEM roadway 

stormwater. 

To address these issues there are three overarching philosophies that could be adopted: 

• Leave the situation as it is; 

• Prevent spill across SH 2 completely in up to a 100 year storm; 

• Balanced spill option – managed spill and mitigate effects. 

Retaining the existing situation is not a desirable option, because it involves an unacceptable level of risk to 

urban areas of Papamoa, including the proposed developments in the Maranui catchment, e.g. on the Asher 

Block. In addition it allows regular spills across the TEM resulting in frequent road closures. 

Preventing a spill across SH2 requires that the full design flood would need to be conveyed in the Mangatawa 

Drain. Given the tight corridor available between the Railway and SH2, this would require the drain to be either 

concrete lined, or at least to have full structural retaining walls both sides over most of its length. This is 

unlikely to gain consent because of the adverse aesthetic and environmental effects it would have on the 

waterway and discharge point and is not viable because of the significant cost. 

It has therefore been concluded that the best approach is the balanced spill option whereby the frequency and 

volume of spills is reduced allowing the character of the existing Mangatawa Drain to be retained, combined 

with improving its flow capacity with some specific works and improved ongoing maintenance. This will 

reduce the risk of flooding across the SH2 and reduce the risk to Papamoa urban area to acceptable levels. 

There are a number of outcomes that the project seeks to achieve in respect of the proposed Mangatawa Drain 

improvements. 

(a) Reduced frequency and volume of flooding across the highway to the north; 

(b) An overflow volume discharged to the Wairakei catchment that is no more than was assumed for the TCC 

comprehensive stormwater consent for that catchment; 






(c) A maximum flood level in the Maranui catchment of 4.6mRL (Moturiki Datum) in the 1% AEP 4 storm; 

(d) Provide for stormwater quality treatment for the runoff from the fully developed Maranui catchment, the 

proposed TEM and the development of the MPBI industrial zoned land, to protect the quality of the 

Harbour at Rangataua Bay; 

(e) Any works on the Mangatawa Drain or any flood ways should be appropriately landscaped to achieve a 

multipurpose and aesthetically pleasing outcome, compatible with proposed adjacent development; 

(f) Any works on the Mangatawa Drain should be environmentally appropriate, and include consideration of 

current and traditional uses, including for whitebaiting; 

(g) A cost effective and affordable solution. 

We have considered the form that the Mangatawa Drain should take, considering the multiple purposes for 

which the corridor would need to serve. The identified objectives and actions are: 

• Stable drain banks, reduced risk of erosion; 

• Riparian planting adjacent to the channel for cover and bank protection; 

• Access for whitebaiting and other stream-related activities; 

• Provide floodway capacity, while retaining multi-use capability for most of the time when there is no 

flooding (e.g. grassed area for picnicking, specimen trees, etc); 

• Access for long term maintenance. 

6.1 Further Engineering Options Considered 

The “Balanced Spill Option” as described above was further investigated during the concept design stage and 

various flood mitigation measures were considered resulting in three options being identified and investigated. 

These were: 

1. Prevent spill across the State Highway east of Kairua Road, allow spills opposite Bruce Road 

2. Prevent spill across the State Highway opposite Bruce Road, allow spills east of Kairua Road 

4 The Tauranga District Plan specifies minimum building platform levels for the Papamoa area, based on a 2% AEP design flood level of 

4.5mRL established some years ago. In recent work by TCC for the comprehensive catchment consent for Wairakei/Papamoa 

Catchment, TCC has also considered the 1% AEP storm, and a design flood level of 4.6mRL. These two values are reasonably 

consistent in terms of the design solution to achieve them, with the 1% AEP storm being the more severe event. Because the 

Mangatawa spills to Wairakei catchment, we have adopted the higher (1% AEP) storm as the basis for design, consistent with that 

catchment, but have also used the 1% AEP storm for the target performance in the Maranui catchment. 






3. Similar spill at both Kairua and Bruce Roads 

Option 3 provided the best cost and hydraulic performance requiring assessment and inclusion of the 

requirements of the Maranui catchment. 

Taking into account the effects of the Maranui catchment with the preferred options alone, the following 

information is required: 

1. Increase the Maranui swale storage capacity 

2. Provide additional outlet capacity from the swale to the harbour 

3. Utilise natural available storage in the Bruce Road rural area 

6.1.1 Outlet and Discharge Points 

At present the Mangatawa/Maranui catchment flood discharge points to the Rangataua Bay are at the outlet of 

the Mangatawa Drain and via the Maranui wetland term. As part of the assessment, four outlet options were 

considered and this is shown in drawings in the attached technical report in Appendix 8. 

1. Pipe the overflow north to the coast at Papamoa Beach through undeveloped land. An approximately 

1.8km long large box culvert is required with potentially a new outlet to the sea. The construction and 

land costs along with the effects on the coast area would be unacceptable and will make this option 

prohibitive; 

2. Pipe the flow west following the railway down the centre of Truman Lane and beyond and out to the 

harbour. This option would require a 2.6 km long large box culvert to the harbour. The same reasons 

as for the above point 1 will make this option prohibitive; 

3. Maranui flood bypass: Take the overflow down Maranui swale to the culvert crossing the State Highway 

and add two additional pipes adjacent to an existing current Maranui culvert; 

4. Mangatawa flood bypass: Leave the existing Maranui outlet as it is, and provide the overflow capacity 

through two pipes back to the Mangatawa drain immediately west of Mangatawa Lane. 

Those four options were narrowed to two principal options based on feasibility and cost, namely Options 3 and 

4 above. More detailed rationale for these decisions can be found in the Options report in Appendix 8. 

In comparing these outlet options, the Mangatawa flood bypass had more merit overall. 

The positives of Option 4 are: 

• The required flood corridor becomes a potential area for recreation at the lower Mangatawa drain location. 

• Leaves more space for the treatment wetland. 






• Has less effect on Special Ecological Site 13. 

• Lower cost overall. 

• Can be integrated with the MPBI development and aesthetics and use of the area and over all uses less land 

than other options. 

• Appears to fit within the riparian area shown on the MPBI development concept, so no change to the 

usable area of the development. 

The aspects where the Mangatawa flood bypass has less merit are: 

• Additional space is required along lower Mangatawa drain for the flood bypass. However less is required 

along the Maranui flood bypass. 

Drawings showing these works in detail are attached 3932036-ck143 to 3932036 ck146 (also Appendix 9). 

The Mangatawa flood bypass (Option 4) is considered to be the preferred option. 






7. Description of the Proposal 

The elements of the proposal that are the subject of this application are the works related to the construction 

and operation of the stormwater management system of the TEM and the works related to the construction 

and operation of the Mangatawa Flood Bypass. These stormwater control devices are linked by the way they 

operate together to manage stormwater in day to day and flood events, but are separate in the issues they 

designed to address. 

The description below addresses each package of activities separately. 

7.1 Mangatawa Flood Bypass Activities 

The following is a summary of the key features of the flood bypass proposal and is further detailed in the 

technical report attached as Appendix 8. 

7.1.1 Increased Drain Storage 

On the eastern side of Kairua Road, enclosed between the rail track and the motorway, a storage area will be 

created by excavating approximately 21,000m 3 - 28,000m³ over an area of 1.2 ha (this will involve excavating 

a set distance from the current railway track allowing for possible track duplication, at a 1V in 5H batter to a 

level set above the current drain). The current drain will serve as the main channel with the new storage area 

set above normal (dry weather flow) water level. The creation of this additional storage will require excavation 

in the drain, conveying of the excavated material and the regrassing of the newly shaped drain and flood plain. 

7.1.2 Top Spill Bund 

Currently there is an earth bund that starts from the rail track where the catchments of the Papamoa hills drain 

under the rail track. This bund will be strengthened and extended and will follow the drain alignment on the 

northern side. 

The bund will be 3 metres wide at the top with a 1 in 3 slope with a total estimated fill volume of 3,000 m 3 – 

4,000m 3 . The bund will follow the rail track alongside the State Highway from chainage 9500 to a highpoint at 

chainage 8950. The bund is designed to be overtopped periodically and therefore will require reinforcement 

and regular maintenance. An earth bund was chosen as it will be easier to maintain with a 3 metre wide top 

and appropriately vegetated batters. The creation of the earth bund will require importing material and 

working alongside the current drain. 

7.1.3 Bruce Spill Stop Bank 

For the Bruce Spill Stop Bank a stop bank will be constructed between the highway and drain from CH7300 to 

CH8700. This may take the form of a concrete crash barrier. The barrier will be designed to operate to allow 

for over topping. 






The height of the barrier above the drain varies and approximately follows the grade of the road. On average 

the barrier is 0.7m high above finish road level. 

7.1.4 Maintenance Work in Upper Mangatawa Drain 

The current drain is overgrown with shrubs and long grass and weeds. It is proposed to remove the current 

vegetation and replant the drain with suitable species of grass and low-growing frangible native plants that 

will aid hydraulic conveyance. 

The bed of the drain is undulating and it’s proposed to level the bed to a more uniform grade. The excavation 

required is in the order of 100 m 3 to 200m 3 

It is noted that currently the drain contains parrots feather and reed sweet grass which are invasive weeds that 

block waterways. This proposed work will result in the removal of this weed in this locality but there will also 

be a requirement for ongoing maintenance to control the weed. 

7.1.5 Rail Bridge Embankment Stability 

The Mangatawa Drain adjacent to and beneath the rail bridge located just east of Mangatawa Lane will be 

modified. The existing drain alignment at the lower rail bridge has to flow through two 90 degree bends when 

passing under the rail bridge. Erosion of the embankments is evident especially on the upstream side of the 

rail bridge. 

The fluctuation of the water levels in the drain, fast flowing water and lack of ground cover can potentially 

worsen erosion. The modelling work undertaken has indicated this section of the drain to be a pinch point 

resulting in high hydraulic losses through this section of the drain. This causes water to backup and increases 

the upstream water level and spills. 

To reduce bank erosion and to reduce the hydraulic losses through this section, it is proposed to improve the 

alignment of the drain cross-section profile and improve the alignment by having smoother transitions before 

and after the railway bridge. The following drain profile is suggested for this purpose: 

1. Bottom width, 8 metre wide 

2. Side batters, 2v in 1h 

3. Top width, 12 metre wide 

The drain profile below the rail bridge will be kept the same and engineering works will be carried out on the 

sides to improve the stability. A combination of “Gabion” walls and “Reno” mattresses are proposed for this 

work. 

“Gabion” walls and “Reno” mattresses are proposed to create a stable cross-section profile that would be able 

to convey flood flow and improve embankment stability. The improving of the drain alignment would occur 

approximately 100m upstream and downstream from the rail bridge and no work is proposed on the bridge 

structure. 






Underneath the bridge itself the drain banks will require structural strengthening to maximise the flood flow 

capacity. This will require works such as providing a tied back, shot crete (sprayed concrete) wall. 

The total volume of earthworks for this activity is 13,000 m 3 – 14,000 m 3 

7.1.6 Flood Bypass from Maranui to Mangatawa 

It is proposed to install two 2.1m diameter pipe culverts under the highway and railway track that will link the 

Maranui swale to the Mangatawa drain. The location of the discharge point in the Mangatawa Drain will be just 

upstream of the Mangatawa Lane Bridge, the Maranui swale will potentially spill 6 times a year over a weir into 

these pipes and flow to the Mangatawa Drain. This bypass would provide an additional flood outlet for the 

Maranui Catchment and a weir will control the flow in such a way as to direct all water up to a third of a 50% 

AEP (water quality event) storm event to the existing outlet for treatment in the Maranui treatment pond. Any 

storm event bigger than the water quality event will spill over the weir to the Mangatawa Drain and thus 

provide additional capacity during flood events for water to drain away. The volume of excavation required at 

this location will be approximately 2200m 3 -3100 m 3 . 

7.1.7 Sandhurst Culvert 

A 1.8 metre diameter culvert under the proposed Sandhurst Interchange will convey Maranui swale flows past 

the interchange. The culvert is estimated to be 70m long with concrete inlet and outlet structures. 

Constructed in conjunction with interchange construction. 

7.1.8 Extension of Maranui Culverts 

The current Maranui swale drains to the treatment pond through a 1.8 metre diameter culvert that is 260 

metres long and passes under SH2 and the rail track. The culvert discharges 120 metres upstream of the 

treatment pond in an open drain. To remove the open drain and release the land for development it is 

proposed to change the current open drain to a culvert. The culvert will be extended with the same size 

culvert up to the stormwater treatment area with a new concrete outlet structure. The proposed extension is 

80 metres long and will require a total amount excavation between 1,500m 3 and 2,000m³. In addition the 

existing 1200mm dia culvert will be realigned to discharge directly into the wetland as shown on drawing 

3932036 ck431, Works C. 

A 750mm dia culvert will be installed to convey stormwater from the TEM alignment to the stormwater 

treatment wetland. This will be installed on or about ch_5800 and will connect an existing pipe to the new 

pipes leading the wetland area. The volume of excavation required for this area is 1,600m 3 – 2,000m 3 . 

7.1.9 Maranui Swale Deepening 

Deepening the Maranui swale will create additional storage capacity within the swale. This will provide for the 

increased runoff from future urban development and the impact of the climate adjusted rainfall. While the TEM 

and the flood management strategy will utilise the swale, additional storage in the swale will only be required 

when the Maranui catchment area is developed further. This aspect of the project is not needed at this time 

and therefore the earthworks related to this activity will not be applied for in this application. Consent will be 

sought at the time of construction. 






The swale bed would need to be deepened by approximately 0.75m. 

7.1.10 Lower Mangatawa Drain (from Mangatawa Lane to Tauranga Harbour) 

The existing lower Mangatawa drain flows in a south western direction to the Rangataua Bay. The drain is 

approximately 800m long, measured downstream from Mangatawa Lane to the Bay. The first 200m of the 

drain has a steep embankment on the eastern side that slopes down to a defined channel which flows on 

average 2.5m wide. On the western side of the channel is a floodplain of about 3m wide after which the 

embankment slopes up to the existing higher ground that is currently being used for farming purposes. 

The lower Mangatawa drain (from chainage 6800 to the harbour) will be modified to create more flood storage 

on the banks of the drain. The existing spoil by the drain will be removed. 

In addition, a stopbank will be created on both sides of the drain to protect the MPBI land from flooding from 

the drain. It will involve the removal of non native trees and trimming of the spoil and replanting with native 

vegetation. 

These stopbanks will be re-vegetated to improve amenity in this area. Maintenance of the drain will be 

undertaken by TCC in future and provision has been made for access of maintenance vehicles. 

The flood corridor and stop bank will continue as far as the ecological sensitive area by the harbour. After this 

point the flow will spread out and flow at a lower level and velocity to the harbour. 

The drain improvements include the following: 

• Planting native grasses along the drain edge. 

• Planting native trees along the drain on both sides outside the 1% AEP storm event flood level. 

• Providing flood plains and batters covered in grass. 

• Provide access for maintenance. 

• Provide a walking track. 

Drawings of the lower Mangatawa drain are attached as Appendix 11 drawing number 3932036-ck431 Rev B. 

7.1.11 Mangatawa Flood Bypass Flood Levels 

The floodwater travelling from Maranui swale to Mangatawa drain via a flood overflow outlet near Mangatawa 

lane. will only be used in larger storm events, exceeding the motorway “first flush” stormwater quality storm. 

Current modelling forecasts predict that the culverts may be used up to 6 times a year. Up to about the 10 year 

storm the flow would only include runoff from the Maranui catchment and the TEM, with no Mangatawa spill 

flow included. Above the 10 year flood, there would be Mangatawa spills also included in the discharge. 






The water levels, peak flow rates and velocity for the preferred option for the 100 year flood are given in the 

table below. These have been determined with a hydraulic model of the drainage system. 

The following table summarises the 1% AEP results along the Maranui floodway at the stormwater treatment 

wetland and lower Mangatawa drain. The current day to day flows along the Mangatawa Drain will remain the 

same. The peak rate however can be higher than the present due to the drain capacity improvements. 

Table 10: Hydraulic Results 1% AEP 

Mangatawa Drain 

Maranui floodway 

Corridor 

Peak flow 

Peak Water 

Peak 

Corridor 

Peak flow 

Peak water 

Peak 

width 

rate 

level (m) 

velocity 

width 

rate 

level (m) 

velocity 

(m) 

(m 3 /s) 

(m/s) 

(m) 

(m 3 /s) 

(m/s) 

Unmitigated 

Current situation 

Mitigated 

Proposed 

A - At drain chainage 3,287m 

B – At extended culvert outlet 

5 17.39 1.82 0.99 24 9.10 1.88 1.45 

25 A 46.92 3.03 1.5 12 B 6.51 1.64 1.35 


The current Stormwater Treatment Wetland is owned by TCC and on land leased from MPBI. It is for the 

treatment of stormwater generated from residential areas within the Maranui catchment. This project will 

maximise the use of this area to treat and discharge stormwater generated by the TEM. In addition to this the 

wetland will be able to accommodate discharges from the MPBI industrial zoned land at Truman lane, and MPBI 

industrially zoned land between Truman Lane and the Mangatawa Drain. 

The final shape and design of the stormwater treatment wetland will be dictated by the developments that are 

proposed to use it. In this instance if the MPBI land is developed to its industrial zoned capacity, the pond 

needs to be enlarged beyond its lease area. An area that could be used is between SES13, the existing 

wetland, and the proposed MPBI development. If MPBI land remains undeveloped the pond will remain within 

the current TCC leased area. 

The design will be able to treat and discharge stormwater to accepted regional water quality levels. Detailed 

drawings and information of this wetland can be found in Appendix 10. 

• The total volume of earthworks required for NZTA TEM works in the proposed stormwater treatment 

wetland is approximately 4,500m³ - 5,500m 3 . This is the subject of this application. 

• The total volume of earthworks required for TCC works in the proposed stormwater treatment wetland is 

16,000m³ - 20,000m 3 . This will be the subject of a future application. 

• The total volume of earthworks required for the MPBI portion of the stormwater treatment wetland is 

17,000m³ - 24,000m 3 . This will be the subject of a future application. 






Overall the total volume of earthworks required for the stormwater treatment wetland is approximately 

45,400m 3 . 

In the future design of the wetland and staging of the works required the following principles have been 

agreed by TCC, NZTA and MPBI achieve an acceptable stormwater treatment area: 

1. Maximise the use of the current lease area 

2. Retain as much of the established trees and plants as possible 

3. Not to encroach on the Special Ecological Site 13 located on the south of the treatment area 

4. Be capable receiving and treat stormwater from TCC’s residential areas, MPBI proposed industrial land 

and the TEM 

5. Not to encroach on the existing and proposed TCC pipeline easements along the western boundary 

6. Apply ARC TP10 design standards for the upgrading of the wetland. 

The following Table shows the stormwater runoff for the water quality storm events and the percentage split 

between the various parties. 

Table 11: Stormwater Treatment Requirement 

Party 

Pervious area 

(km 2 ) 

Impervious area 

(km 2 ) 

Catchment area 

(km 2 ) 

Volume required 

(m 3 ) 

TCC 

0.79 1.75 2.54 12,941 

(Maranui and Arataki) 

MPBI 

0.01 0.45 0.46 11,635 

(Industrial) 

TEM 

0.04 0.15 0.19 3,247 

(Motorway) 

Total 0.84 2.35 3.19 27,823 

The current available leased area is too small for the stormwater treatment required for all developed land 

scenarios as shown above. There is a potential 5 ha low lying area available east of the current pond area, 

enclosed between MPBI southern boundary and the Special Ecological Site. The additional treatment area 

extends into that land and is shown in the technical report attached as Appendix 10. The report shows the 

layout and cross-section drawings for the extended treatment area. 






7.2 TEM Roadway Stormwater 

The package of activities this part of the report refers to are between chainage 5250 – to 10850 in the 

Mangatawa catchment. This part of the report describes the devices and design related to controlling and 

treating the stormwater generated by the road up to the point it leaves the swales to discharge to the 

surrounding land/drains or water. 

It should be noted that NZTA has received consent (albeit appealed to the Environment Court) for stormwater 

resource consents for the remaining three catchments that are affected by the TEM, i.e. Te Maunga, Bell Road 

and east of the Kaituna River. The stormwater system that is subject to this application is shown in 

Appendix 3. 

7.2.1 TEM Stormwater Management Philosophy 

The main method for stormwater management is to use swales for stormwater treatment, attenuation and 

conveyance, with discharge into the existing drainage network. In this area ALL the stormwater generated by 

the road will be treated and attenuated in swales on the northern side of the alignment. Water will be collected 

in catch pits from the southern side of the road and piped to the swales which represent a change from the 

present situation where the water from the existing Sate Highway drains into the Mangatawa Drain. 

The following summary sets out the principal elements of the approach proposed for the TEM component of 

this proposal. 

1. Treatment and conveyance in Maranui catchment using the TCC drainage system; 

2. Swales in the Wairakei catchment providing treatment in accordance with TP10, plus flood storage in 

accordance with the TCC Wairakei stormwater discharge consent (currently subject to appeal); 

3. Fit in with existing land drainage system as far as practicable; 

4. Discharge frequently to existing streams or drains, to avoid the concentration of large flows at fewer 

discharge points; 

5. Design using Tauranga City Council (TCC) updated rainfall values that account for climate change 

(2055); 

6. Design consideration up to 1% Annual Exceedance Probability (AEP) storm, but with pipe systems 

designed for the 10% AEP storm with the balance as secondary flow. 

7.2.2 Swales 

The drainage system will generally consist of kerb and channel on the southern side of the proposed TEM 

collecting runoff and piping it north at regular intervals under the TEM to swales along the northern side. 

Within the Wairakei catchment (from chainage 8,200 to 10,850), these swales will provide treatment and 

attenuation before discharge with a pond within the designation North West of the Domain Road interchange. 

Within the Maranui catchment, the swales are principally for conveyance, as the treatment will occur in the 






Maranui stormwater wetland, and the Maranui swale has significant capacity to accept the flows. In the section 

east of Bruce Road (chainage 9200 to 9,950) the swales will provide attenuation as they will be discharging 

initially to an existing drainage system which then joins the Maranui swale. West of Bruce Road discharge will 

be direct to the Maranui swale, as a separate TEM swale system is not necessary. 

The swales will be at relatively flat grades, often less than 1%. Given that the land being traversed is either 

peat or soft alluvial silts (using wetland swales at or near groundwater level) the flat grades are not expected to 

be a problem in terms of ponding of water. However, the swales and associated pond at the Domain Road 

interchange will provide attenuation of flood peak flows from the motorway, and have been designed to meet 

the requirements of the TCC comprehensive catchment consent for Wairakei catchment. Some restriction of 

outlet flows from the swales to the receiving drains is needed to achieve a neutral effect on peak flows and 

fully mobilise the in-swale storage. A drawing of a typical road side swale is also provided in Appendix 12 

Drawing 2036-ck227 Rev D. 

Between chainage 5700 and chainage 7900 the TEM will drain directly to the Maranui swale and receive 

treatment in the enlarged TCC wetland at the end of Truman Lane (see Appendix 4 drawing no: 3932036- 

ck073). 






8. Consultation 

8.1 Background – Tauranga Eastern Motorway 

Consultation for the TEM project began during the designations phase of the project from 1998 – 2000. 

During that process the community, Tangata Whenua, stakeholders and landowners were consulted on the 

proposed arterial. In 2007 the community was consulted about changing the classification of the Arterial route 

to Motorway. 

In 2008-2009 the same communities were consulted on the project resource consents for earthworks, 

bridging, water take and stormwater management. A full programme of newsletters, open days, hui and 

individual meetings has occurred. 

It is clear from the current consultation programme that the majority of landowners, community and 

stakeholder groups’ concerns have been recorded and addressed through the original designation and 

classification processes. When informed of the purpose of this round of resource consent consultation, in 

general the responses supported the TEM project and wanted to see its construction completed as soon as 

possible. 

8.1.1 Consultation Objectives 

Consultation for this Mangatawa Stormwater consent targeted four directly affected groups – MPBI, other 

directly affected land owners, Tangata Whenua, and the wider community. The objectives of this consultation 

process were to inform people of the proposed methodology for constructing and operating the motorway, 

management of the stormwater to reduce the effects of flood spills across the State Highway 2, and to receive 

their opinions on the project. Their feedback and responses are recorded as follows. 

8.2 Mangatawa Public Consultation 

The NZTA issued a project newsletter on the 17th of November 2008 which was mailed out to approximately 

2500 residences in the wider catchment area as well as approximately 500 to the directly affected parties, 

adjacent landowners, affected stakeholders, Iwi, Hapu and other parties. The newsletter was a two sided A4 

flyer detailing the proposal and outlining some options, and included a conceptual diagram of the existing and 

proposed drainage for the Maranui swale and Mangatawa drain. It also invited recipients to an Open Day 

where the project team and client would be present with additional information about the project to answer 

questions and receive feedback from the public. This Open Day was held on Thursday 4th December 2008. 

The public were given two weeks from the Open Day to provide feedback. Six people in total attended the 

Open Day and made no formal comment. 






8.3 Directly Affected Landowners 

All landowners on the northern and southern side of the Mangatawa drain and Maranui swale from chainage 

5900 to 10800 were contacted and offered a meeting for consultation about the potential effects from this 

application. Meetings were held between 11th and 22nd of February 2009 with individual landowners at a site, 

date and time of their choice. 

Two Cottage meetings were held on the 4th and 9th of December 2008 with landowners adjacent to the 

project area to inform them of the latest developments in the project, how these will affect them and for the 

technical team to consider their concerns. Only 3 people attended in total and they expressed positive 

comments about the project. These landowners were also invited to the public Open Day held on Thursday 4th 

December 2008. 

The names of the land owners invited to cottage meeting can be provided if required. 

8.4 Individual Landowners 

Individual landowners directly affected by the existing drainage were consulted in separate meetings. NZTA 

has endeavoured to address all the concerns that arose at these meetings as well as providing information. 

These landowners were also invited to the public Open Day held on Thursday 4th December 2008. All invitees 

were given two weeks opportunity to provide feedback on the project. The names of the owners can also be 

provided if required. 

The owners of the land raised concerns that centred on the way the NZTA and TCC were going to deal with the 

flooding issues in the area. A summary of the issues raised were: 

• Water residence times after flooding, i.e. the time it takes for floods to recede 

• Culvert heights, flow paths and drains blocking 

• Lack of drain maintenance in the Mangatawa Drain 

• Swale planting (no trees in them so they can be maintained) 

8.4.1 MPBI 

MPBI owns the land adjacent to the Tamapahore Marae on which they propose industrial development. The 

site also includes an existing drain which takes the flood waters to the harbour as well as draining the site 

itself. NZTA and TCC have consulted with MPBI in 2008 and 2009 to provide feedback on the options for this 

proposal. Meetings have been held with the MPBI Board, technical advisers and MPBI’s engineers who provided 

input and reviewed the Options Study Report dated March 2009. 






The meetings were held on: 

• 15 Feb 2008 – TEM Overview. 

• 8 July 2008 – TEM Interchange. 

• 21 Aug 2008 Workshop – TEM and TCC stormwater application. 

• 9 Sep 2008 – Mangatawa drain and possible mitigation measures. 

• 18 Dec 2008 - TEM and TCC stormwater application. 

• 29 Jan 2009 – TEM + TCC Stormwater and roading issues. 

A summary of issues raised at these meetings relevant to this proposal are outlined below. 

Table 12: Summary of Issues Raised 

Issues raised 

Possible flow path for flood waters west through 

TCC Land. 

Protection of the future develop-ability of MPBI 

land. 

Construction of an Earth Bund along Mangatawa 

Drain to protect building platforms. 

Concern for potential removal of whitebait habitat 

and eel holes. Riparian enhancement of lower 

Mangatawa Drain after works are completed to 

retain whitebait and eel habitat. 

Requested the extension of the Maranui swale 

outlet pipe to wetland to increase developable area. 

Drain maintenance. 

Existing stormwater treatment pond designed as a 

wetland to protect water quality of harbour. 

Accommodation of MPBI stormwater from future 

industrial land in wetland design. 

Connection of Truman lane stormwater to 

treatment wetland. 

Response 

Discounted by options selection process as 

technically difficult and costly 

Provision of the bund next to the Mangatawa Drain 

and the extension of the culvert from the Maranui 

Swale to the wetland. 

Included in the over all design concept and will be 

part of the construction of the TEM. 

Included in the over all design concept and will be 

part of the construction of the TEM. 

Included in the over all design concept. However 

not planned as part of the construction of the TEM. 

TCC to undertake maintenance 


only the TEM component will be part of the 

construction of the TEM. 










The proposal has the potential to benefit the planned future development of MPBI and the proposed 

developments along Truman Lane. Including the effects of the MPBI industrial developments in this 

stormwater assessment gives MPBI the potential to gain consent for its future stormwater discharge into the 

harbour from its development as part of this process. 

8.5 Tangata Whenua 

The TEM project crosses environments that are of cultural significance to many iwi and hapu. As such, during 

the Notice of Requirement/Designation phase between 1998 and 2000, which included alignment option 

selection and assessment of the environmental effects of the preferred alignment, the assessments were 

undertaken in consultation with the Tangata Whenua parties. 

The summary record of consultation provided with this application is built on consultation undertaken during 

the designation phase, the regional resource consent phase of the TEM between Domain Road and Paengaroa 

for stormwater and the regional resource consent phase between Te Maunga and Paengaroa for earthworks. 

Te Arawa have always requested copies of newsletters and minutes as a watching brief and indicated that they 

no longer wanted direct involvement in consultation about the resource consents required for the TEM project. 

8.5.1 TEM Project Hui 

The Beca team has also made a presentation to the Combined SmartGrowth Tangata Whenua Forum. Initial 

calls and hui were held in the December 2007 – January 2008 period to determine the nature of the 

consultation then two additional technical meetings were held with each hapu. The exceptions to this process 

were Te Arawa who advised that they did not wish to be involved in the hui but would be kept informed of the 

process by mail. Nga Potiki intend that the same process is followed albeit with the Hui a Hapu beginning in 

May 2008. 

Following the initial hui with an introduction to the project and the agreement as to how the consultation 

would be undertaken, the first hui a hapu described; 

• the earthworks process and the significant volumes of material that are to be moved about the alignment 

and brought in from elsewhere, 

• the stormwater management system, 

• the Kaituna River Bridge, and 

• Alterations to the Designation bands. 

A draft of the Principal's Requirements that define the contractors' responsibilities for environmental 

management during construction was circulated for information. Copies of the archaeological surveys 

undertaken of the route and supplied in the assessment of environmental effects for the Designation were 

supplied to those that requested additional copies (to that originally received). On the basis of the feedback 

received from the first round of meetings a joint hui and bus trip was undertaken on the 25 th March to provide 

familiarisation of the alignment as well as discussing further the earthworks process during construction. 

The Second hui a hapu discussed: 

• The cultural response to the earthworks proposed. 






• Stormwater management under the ARC guidelines and the behaviour of stormwater in wet and dry swales. 

• Water take for dust suppression. 

• Draft landscape plans particularly vegetation species. 

• Support for a project specific TEM Tangata Whenua Advisory Group (TEMTWAG). 

The Tauranga Eastern Motorway Tangata Whenua Advisory Group was formed to facilitate discussion and 

agreement on cultural matters associated with the project. The formation of protocols and agreements 

regarding earthworks is one such possible outcome. 

8.5.2 Mangatawa Floodway Application Hui 

The following Iwi and Hapu have an interest in this specific proposal and a record of their views is summarised 

below: 

1. Ngaiterangi Iwi; 

2. Nga Potiki Hapu; 

3. Ngati Pukenga Iwi; 

4. Ngati He Hapu; 

5. Waitaha; 

6. Ngai Tukairangi Hapu. 

Ngaiterangi 

A cultural impact assessment undertaken for the TEM project and Ngaiterangi instructed that it be used for this 

assessment and is provided in Appendix 5 of the application. On receipt of this Assessment of Environmental 

Effects they may have additional responses which will be recorded and provided to EBOP and TCC. 

Nga Potiki 

A hui was held with Nga Potiki on 14th October 2008 regarding the Mangatawa Floodway and TEM project. 

The hui discussed the options and possible solutions concerning reducing flooding in the Wairakei and 

Maranui catchments while managing the stormwater generated by the TEM. 

Some of the concerns relevant to the effect of this application raised at this hui are summarised as follows: 

• An interest in the species of vegetation used in swales to be sure they are native. 

• The source of the fill for earth works and a concern that it not be waahi tapu. 

• The volume of water in the Mangatawa Drain and the potential for increased flooding of the MPBI land. 






• The quality of stormwater discharge and its effects on Tauranga Harbour. 

• One suggestion was that the stormwater from the TEM be conveyed westwards to the other side of the Bay 

Park Stadium to a TCC pond and wetland before reaching the harbour. This option was considered by the 

engineers and discounted due to cost and feasibility of achieving this outcome as shown in the attached 

options report. 

Ngati Pukenga 

A hui was held with Ngati Pukenga on 15th of February 2009. Representatives of the hapu met with members 

of project team, NZTA and TCC. The following issues were raised. 

• Water quality of the discharge to the harbour 

• Flooding effects on the farmlands beside the State highway especially Kairua Rd flooding 

• The significance of harbour shellfish and the need to protect the habitat 

• Long term effects of stormwater run off sedimentation contamination 

• White baiting and the fish spawning periods for white bait on the lower drain and opportunity to encourage 

the fishery there by enhancement 

• Mangatawa catchment land flooding residence times 

A copy of the AEE will be provided and should any additional consultation responses be received that will be 

forwarded to EBOP and TCC. 

Ngati He 

Ngati He was contacted regarding the Mangatawa application on the 9 th February 2009. They requested to be 

sent a newsletter regarding the proposal for dissemination at a hapu meeting and the draft application when 

finalised. A copy of the AEE will be provided and should any additional consultation responses be received that 

will be forwarded to EBOP and TCC. 

Waitaha 

At the TEM Tangata Whenua Advisory Group meeting in February Waitaha requested a copy of the AEE and may 

provide comment. 

Ngai Tukairangi 

Ngai Tukairangi representatives were contacted on the 19 th of December 2008 and sent information to present 

at an internal hapu meeting. Members of the hapu were asked to express any concerns with the proposal and 

contact the project team. No concerns were raised with the project team and the hapu representatives were 

sent more material in case other members became interested. 






8.5.3 Tauranga Eastern Motorway Tangata Whenua Advisory Group 

A series of joint Tangata Whenua forums were organised and held in May, July, September, October, November, 

and December 2008, and February 2009 where representatives from the following iwi and hapu were in 

attendance to discuss the earthworks protocol for the project and the NZHPT application: 

1. Ngaiterangi; 

2. Nga Potiki; 

3. Ngati Pukenga; 

4. Te Arawa; 

5. Waitaha; 

6. Tapuika; and, 

7. Ngati Whakaue. 

The TEM TWAG group discussed the final changes to the Earthworks protocol at the December 1 st 2008 

meeting. While this application has been discussed and presented to this group in only a minor way, the Hapu 

affected by the application have been met with separately as described above. It is envisaged that the 

Earthworks Protocols will be applied to the site. This provides continuity for the project as a whole with the 

rest of the TEM project consents. 






9. Assessment of Environmental Effects 

This assessment considers the effects of the proposal in its entirety dealing with the works related to 

stormwater and earthworks. 

9.1 Stormwater Management 

Stormwater has the potential to adversely affect receiving watercourses. Flow volume can affect flooding in 

areas within a given catchment. 

The construction of the TEM and Mangatawa flood bypass has two potential effects on stormwater and 

receiving environments: 

• Water quantity and associated flood risk, including both drain capacity and ponding in low-lying areas; 

• Water quality (non point source pollution) caused by the discharge of contaminants associated with 

highway traffic, particularly including sediment, hydrocarbons and heavy metals. 

9.1.1 Water Quantity 

The existing flood risk in this area is described in the technical report attached to this document (Appendix 8). 

In the 18 May 2005 storm extensive ponding occurred in the Papamoa area. The Mangatawa Drain alongside 

the motorway overflowed at two locations. 

The aim for NZTA is to reduce as much as practicable the frequency of stormwater overtopping and 

overflowing the motorway, while TCC’s aim is to reduce the volume of water that would enter the Papamoa 

catchment areas (Maranui and the Wairakei). In practice, full containment is not practicable. 

The flood risk assessment undertaken for the stormwater management system proposed for the TEM has used 

update data for climate change (2055) and as such the effect of flood risk has been addressed 

comprehensively. 

TEM Roadway Stormwater 

The TEM will increase the volume of runoff in this catchment and the road embankment will remove some 

existing flood storage, although the latter effect is less than minor. The combination of these has the 

potential to have an adverse effect in relation to flood risk. 

The stormwater in this area spills across State Highway 2 from Mangatawa to Maranui. From the road, the 

stormwater traverses into swales which treat and attenuate the water in day to day events before discharging 

to drains. Once the water has spilled into the Mangatawa catchment it will make its way overland (as it does 

currently) to the Maranui Swale. At this point 2 x 2100 culverts will be placed underneath the TEM to convey 






excess flood waters from the Maranui swale south into the lower Mangatawa drain at Mangatawa Lane. These 

will be set so the ‘first flush’ stormwater travels to the TCC wetland via the Maranui Swale and the remaining 

diluted flood waters will travel down the Lower Mangatawa Drain. This element of the proposal is vital to this 

proposal as it conveys water in large scale flood events away from the Treatment wetland preventing potential 

damage to that facility from extreme flood events. 

This element of the proposal reduces the flood risk to the Papamoa catchments (Wairakei and Maranui) from 

the present situation. 

Mangatawa Flood Bypass 

i. Upper Mangatawa Drain (Domain Road – Bruce Road) 

The primary aim of the Mangatawa bypass is to control the number of motorway closures and the volume of 

water spilling into the Maranui and Wairakei catchments without negatively affecting the surrounding 

environment. 

The frequency and volume of water spilling across the motorway will decrease with the proposal. It is forecast 

that the spill occurrence will decrease from approximately 3 yearly events (at present with climate change) to 

8. With the proposed mitigation measures the flooding across the motorway is expected about every 10 years. 

The effect of diverting this flood volume on the Mangatawa drain is considered to be minor and will have 

positive effect on the Maranui and Wairakei catchments. 

ii. 

Lower Mangatawa Drain (Bruce Road – Rangataua Bay) 

While there will be reduced risk of flooding in the Wairakei and Maranui catchments, there is potentially 

increased flood risk on the low lying land near the lower Mangatawa Drain (below Mangatawa Lane), south of 

the railway. 

The mitigation measures required to address this issue is to remove spoil and widen the flood plain and to 

provide an earth bund to contain the additional flow particularly the extra peak volume of water and convey it 

to the Rangataua Bay. Once past this area the discharge of the Mangatawa Drain to the harbour becomes 

diffuse, within the SES 13. 

The creation of capacity for flow in the lower Mangatawa Drain will provide the necessary mitigation to reduce 

the effects of increased volume and flow rate of water to no more than minor. 

9.1.2 Water Quality 

The following information has been taken from the Bioresearches Report: Ecological Features of Some Habitats 

within Rangataua Bay Catchment (attached as Appendix 5) and the Tauranga Eastern Motorway Resource 

Consent application. The following focuses on the ecological effects of the TEM project and in turn the 

enlargement of the stormwater treatment pond at Te Maunga. 






The water quality in the area is influenced by the source of the water. The Mangatawa Catchment in the 

Papamoa Hills lies within Western Bay of Plenty District. It is likely that the water quality is influenced by the 

rural runoff in this area but this proposal will not address that issue. However the existing State highway 2 as 

mentioned drains directly to the Mangatawa Drain and it is proposed to pipe this water to swales on the 

northern side of the alignment for treatment and attenuation. This represents a net improvement for the 

Mangatawa drain in terms of water quality. 


The southern side of State highway 2 currently drains directly to the Mangatawa drain and surrounding land 

drains. In addition the surrounding land use is predominantly rural which adds nutrients to the existing runoff 

from the area in the Mangatawa Drain. 

The stormwater generated by the road has the potential to contain contaminants, which can adversely affect 

receiving environments. The concentration of contaminants in stormwater varies during a storm, from storm to 

storm, and from catchment to catchment. 

Stormwater from high traffic areas has a greater potential to contain significant levels of contaminants and 

levels of contaminants in stormwater can change over time, for example as traffic volumes increase. 

The following are some of the contaminants that can be found in roadway derived stormwater. 

(a) Suspended sediments: These are soil, organic particles, and breakdown products of the built 

environment entrained in stormwater flow. 

(b) Oxygen demanding substances: These are soil organic matter and plant detritus which reduce the 

oxygen content of water when they are broken down by chemical action and by bacteria. 

(c) Metals: A variety of trace metal compounds are carried in stormwater in both solid and dissolved 

forms. The most commonly measured metals of concern are zinc, lead, copper and chromium. Metals 

are persistent; they don’t decompose and they accumulate in sediments, plants and filter feeding 

animals such as shellfish. 

(d) Hydrocarbons and oils: The hydrocarbons in stormwater are generally those associated with vehicle 

use. They may be in the form of a free slick, oil droplets, and oil emulsion and in solution or absorbed 

to sediments. 

(e) Litter: Litter in stormwater is often referred to as gross pollution. It has a high visual and amenity 

impact, but limited effect on public health and ecological standards. 

In addition to the above contaminants, stormwater discharges have other physical and chemical effects which 

affect aquatic organisms and change how contaminants react. These include increased temperature, altered 

pH, reduced dissolved oxygen, and changes to alkalinity, hardness and conductivity. 

From chainage 5900 to chainage 7900 the TEM discharges to the Maranui swale directly. The Maranui swale 

does not provide treatment as such but this water will be treated in an enlarged stormwater treatment wetland 

near the end of Truman Lane. This wetland will treat the stormwater to the ARC TP 10 level. 






From chainage 7900 to 9550, within Maranui catchment and east of Bruce Road, the discharge will be to a 

farm drainage system that subsequently discharges to the Maranui swale. This water will also receive 

treatment in the stormwater treatment wetland. The use of swales for initial conveyance will also provide some 

treatment before discharge to the farm drains. 

Within the Wairakei catchment, swales will be used for treatment to remove contaminants, before discharge to 

the farm drainage system. This is because there is no formal treatment provided in the TCC drainage system 

downstream of this discharge. Swales will improve the stormwater quality by reducing contaminant loadings in 

the water. Low velocity in the swales will facilitate the settling of sediments and the vegetative growth will trap 

additional suspended sediment. The swales in this section will be planted with wetland species, as they will be 

set at the drainage system level in peat soils, and will normally be wet. 

The swales will be an effective stormwater treatment measure and will provide treatment for the TEM 

stormwater runoff in accordance with ARC TP10. This level means that the treatment in the swales will reach 

around 75-80% removal rate if the ARC standards are applied. 

The contaminant loads from the footprint of that part of the TEM project for which consent is being sought are 

summarised in the following table. 

Table 13: Contaminant Discharge Summary 

Receiving Environment 

Total Contaminant Loads (kg/yr) 

Sediment Copper Zinc 

Wairakei catchment 

from TEM 

Current 1,988 0.3 1.1 

Proposed 567 0.1 0.4 

Change 1,421 

⇓ 

0.2 

⇓ 

0.7 

⇓ 

Rangataua Bay from 

TEM 

Current 12,510 1.3 5.5 

Proposed 3,948 0.8 2.7 

Change 8,562 

⇓ 

0.5 

⇓ 

2.8 

⇓ 


Maranui catchment 

Current 11,680 14.0 9.6 

Proposed 5,840 9.3 5.3 

Change 5,840 

⇓ 

4.7 

⇓ 

4.3 

⇓ 


MPBI Industrial 

Current 22,600 1.8 6.8 

Proposed 13,560 23.5 13.6 

Change 9,040 

⇓ 

21.7 

⇑ 

6.8 

⇑ 






Receiving Environment 

Total Contaminant Loads (kg/yr) 

Sediment Copper Zinc 

Total 

Current 48,778 17.4 23.0 

Proposed 23,916 33.8 21.9 

Change 24,862 

⇓ 

16.4 

⇑ 

1.1 

⇓ 

It can be seen from the above Table that overall there is a reduction in contaminant discharge from the TEM 

and Maranui catchment due to the increased treatment of storm water over the existing system. The current 

TCC Maranui urban area is not fully treated to the TP10 standard; however, after the works it will be fully 

treated to that standard. MPBI has not yet been developed, so there will be an increase in metals as a result of 

industrial development, despite treatment. At present the TEM is partially treated and the proposed treatment 

more than offsets the increased area and traffic. 

With the appropriate measures in place, adverse environmental effects of the stormwater system on hydrology, 

flood risk and water quality will be mitigated and overall will be no more than minor. 


Water quality was measured by Bioresearches at several locations and there is only one site in the Mangatawa 

Flood Bypass area. Water quality information regarding this site is presented in the above sections. 

The Mangatawa Drain currently discharges directly into the Tauranga Harbour and spills across State highway 2 

at Kairua and Bruce Roads during significant flood events. This proposal will redirect much of this rural runoff 

overspill down the Mangatawa drain and is not expected to have any significant effects in relation to water 

quality. In addition to this when water overtops the stopbanks the water will travel across the State highway to 

the Maranui swale and back to the Mangatawa drain via 2 x 2100 culverts. This will only occur in significant 

flood events and will not significantly affect the quality of the water entering the drain. 

The effects on water quality arising from the Mangatawa flood bypass structures will have a less than minor 

effect on the receiving environments. 

9.1.3 Freshwater Ecology 


The main concern with regards to the effects on the ecology of the freshwater habitats is the potential to cause 

temporary negative effects on the downstream receiving environments, through sediment inputs from 

construction and maintenance operations. Excess sediment loads can affect macro invertebrate communities 

and have the potential for direct and secondary effects on fish communities. Such effects can be minimised 






through the use of appropriate sediment control devices, as outlined in the Bay of Plenty Regional Council’s 

Erosion and Sediment Control Guidelines for Land Disturbing Activities (2001). 


As with the proposed TEM roadway Stormwater option, a main concern is the potential to cause temporary 

negative effects on the downstream receiving environments, through sediment inputs from construction and 

maintenance operations. In addition during operation the flood control structures that convey water need to 

be able to allow for fish passage. This also applies to the upstream migration of native fish and any instream 

works should be carried out, outside of key migration periods. 

The temporary negative effects caused by excess sediment loads should be minimised through the use of 

appropriate sediment control devices, as outlined in the example erosion and sediment control plan attached 

as Appendix 13. This has been informed by the Bay of Plenty Regional Council’s Erosion and Sediment Control 

Guidelines for Land Disturbing Activities (2001). 

With respect to the freshwater ecology of the Mangatawa Drain, as the proposed activities will result in an 

increase in the amount of riparian vegetation present, this will be of benefit to the aquatic habitats within the 

drain, providing shading and cover for fish and macro invertebrates, and increase the potential for the drain to 

act as a pathway for native fish inhabiting the upper catchment. As the riparian planting will be largely 

confined to the lower reaches of the drain it is unlikely to result in a significant change to the water quality of 

the existing drain. 

Stormwater Treatment Wetland 

i. Vegetation 

The element that has the potential to have the most significant effect on the ecology of the area, because of 

the quality of the existing habitats, is the enlargement of the Stormwater Treatment Wetland and the outlet to 

Rangataua Bay. 

With respect to the vegetation and flora within the stormwater treatment wetland, the enlargement of this 

pond preserves most of the large cabbage trees on this site, then the effect of the overall enlargement on this 

component of the vegetation will be no more than minor. 

As an enlarged bund will separate the salt-marsh of the SES from the treatment wetland this is likely to 

promote the growth of the jointed rush which already dominates this area of the pond. The planting of Carex 

in the pond and the forebay has the potential to provide nesting habitat. With respect to the Baumea, shown on 

the planting plans in both the stormwater pond and the forebay, this could grow to such a degree as to 

eventually fill the pond system, and therefore has the potential to lower the overall capacity of the pond. 

Provision needs to be made for several ramps down to water level to allow periodic cleaning of the pond. 

With respect to the potential effects of this proposed development and increased discharge of treated 

stormwater into Rangataua Bay examination of existing data on the sediment quality and ecology of the bay 

(Section 6) indicates that the proposed increased discharge to the Bay will not have a significant adverse effect 

of the water, sediment and overall ecology of the Bay. 






The sediment quality in Rangataua Bay is high (concentrations of trace metals, and hydrocarbons less than the 

guideline values for the protection of aquatic ecosystems or less than the limit of detection), even though this 

section of the Bay has been receiving untreated stormwater from the existing highway. The quantity of 

sediment that will be discharged into Rangataua Bay following treatment will be reduced by about 51% and the 

zinc loads discharged to Rangataua Bay will also reduce by about 4.8%. These reductions represent a net 

improvement in the discharge of contaminants to Rangataua Bay. The annual copper loads being discharged 

to Rangataua Bay will increase by about 94%, however, because sediment copper concentrations in Rangataua 

Bay are below guideline values the increase in copper is unlikely to cause these guidelines to be exceeded. 

This increase in copper concentrations will not have a significant adverse effect on the sediment quality of the 

Bay. 

The proposed enlargement of the treatment pond will not encroach on the Special Ecological Area therefore 

most of the more significant vegetation within the existing pond area will be retained. The effect of the 

proposed development on both the vegetation and the avifauna is therefore no more than minor. 

The proposed discharge to Rangataua Bay is unlikely to have significant adverse effects despite an increase in 

copper concentrations, though a monitoring programme that includes sediment copper concentration in 

Rangataua Bay may be appropriate to ensure copper concentrations do not accumulate to levels exceeding 

guidelines. 

ii. 

Herpetofauna 

Rainbow skinks are an introduced species from eastern Australia and are locally abundant within the Tauranga 

area. The rainbow skinks within storm water treatment wetland were visually estimated to be abundant. 

Because this species is not native to New Zealand, their protected status is currently under review. Rainbow 

skinks are unlikely to be of conservation concern and should not warrant any mitigative effort. 

Copper skinks are a protected endemic species. Given the survey effort, the six individuals located within 

storm water treatment wetland suggest that there is a low to medium-density population onsite, which should 

warrant mitigative effort. This would involve a small-scale pre-construction rescue and relocation of native 

skinks into adjacent or nearby areas of suitable and secure habitat. This action should not require a formal 

translocation, however the Department of Conservation and affected iwi should be consulted. The following 

recommendations should be considered: 

• Retained habitat will require isolating with a silt fence to prevent relocated skinks from returning into 

footprint habitats 

• Retained habitat will require instalment of additional refuges, including small log piles to provide for a 

possible increase in density of skinks within these areas. 

• Retained habitat will require enhancement with additional plantings of low-lying scrub-type plants and 

grasses. Enhanced areas should not be restricted to island areas surrounded by water. 

Predator control would also required until at least such time as any additional plantings have established and 

relocated lizards have re-established micro territories. 






9.2 Earthworks 

The Earthworks for the construction of the TEM embankment and associated swales has been assessed and 

considered at a hearing finishing on December 18th 2008. This application will address the earthwork effects 

related to the construction of the Mangatawa Catchment Stormwater management. 

The total volume of earthworks required to be undertaken is approximately between 45,000m³ - 60,000m³. 

NOTE: This excludes the works which will be subject to a separate resource consent application. 

The effects of earthworks and construction can result in increased, erosion, sedimentation, nutrient levels in 

riparian margins and waterways as well as more human effects such as increased noise, dust and vibration. 

This can have an adverse have an adverse effect on ecological values, cultural values, natural character and 

landscapes. 

9.2.1 Ecological Effects from Construction 

For this proposal there is a potential temporary adverse effect on the ecology of the freshwater habitats in the 

downstream receiving environments, through sediment inputs from construction and maintenance operations. 

During construction the main activities with the potential to generate harmful ecological impacts are: 

1. Works in the bed of the upper Mangatawa Drain 

2. Construction of the stormwater treatment wetland 

3. Construction of the earth stopbank on the Lower Mangatawa Drain 

NZTA and TCC will seek to manage and mitigate these effects through establishing environmental bottom lines 

in its contract documents with the contractor. 

It is recognised that the upper and lower drain has significant importance to the local community. The use of 

the drain to eel and catch white bait was raised during consultation and to support this activity works in the 

bed of the stream will be undertaken outside fish spawning periods to lessen the impacts of this disturbance. 

Works to improve and stabilise the drain alignment past the railway bridge, using gabion baskets and reno 

mattresses, will be undertaken as quickly as possible to minimise disturbance. The banks of the drain will be 

re-established and planted as soon as is practicable after the activity takes place and it is proposed that any 

complaints and or issues that the community may have be dealt with quickly and directly with the contractor 

through a complaints phone line set up for this project. 

The result of these mitigation measures will mean that the effects of this activity will be no more than minor. 

The construction of the stormwater treatment wetland will take place next to the SES as described in the 

project description. Using a Construction Management Plan (CMP) as defined below will address many of the 

issues related to earthworks for this and other earthworks activity. 






An overarching CMP will identify the effects of this work, how the contractor will avoid, remedy or mitigate the 

effects including compliance with the Outline Plan, Resource Consent conditions and Designation conditions. 

The Construction Management Plan (CMP) includes the preparation of an Erosion and Sediment Control Plan 

(ESCP) which will cover how erosion and sedimentation will be managed and mitigated, as well as including 

stormwater management techniques. 

The ESCP will comply with the guidelines set out in the EBOP Erosion and Sediment Control Guidelines for Land 

Disturbing Activities (September 2001). An example Erosion and Sediment Control Plan is provided in 

Appendix 13. This will be developed by the Contractor for approval of EBOP before works can commence on 

site. 

The inputs shall as a minimum include the following: 

• Locality map; 

• Site plan showing the extent of earthworks, type and location of erosion and sediment controls and off site 

sources of runoff; 

• The design for erosion and sediment control ( in accordance with the EBOP Erosion and Sediment Control 

Guidelines for Land Disturbing Activities (September 2001); 

• Engineering drawings and specifications; 

• Details of stabilisation measures; 

• Contingency plans; 

• Construction schedule; and 

• Monitoring and maintenance schedules. 

With regards to herpetofauna, habitats surrounding the wetland were not surveyed, but it is likely that copper 

skinks will be present in areas of scrub vegetation and rank grasses. It is considered unlikely that skinks or 

other native reptile species will be present within grazed pasture or other areas consisting of short grasses. 

The habitats in which the earthworks will be undertaken predominantly comprise grazed and cropped farmland 

that contain no vegetation and flora, wildlife, copper skinks around wetland and amphibians of note, these 

earthworks will have a less than minor effect on the terrestrial habitats of the area. 






9.2.2 Noise and Vibration 

The construction of this project will result in additional noise and vibration through the use of construction 

machinery. NZTA will minimise construction effects such as noise, and vibrations and traffic disruption in the 

following way. 

The Contractor will prepare and implement a Construction Noise Management Plan (NMP). The NMP shall aim 

to minimise any adverse effects from noise during construction, and shall include: 

• The implementation of the principles contained in NZS 6803:1999 and the Outline Plan and Resource 

Consents during the construction of the motorway and local roads; 

• Means to ensure that the Resource Consent requirements are achieved. 

A Vibration Monitoring and Control Plan will be developed to minimise possible nuisance from construction 

works at adjacent sensitive building and/or occupants. Maximum permitted ground vibration levels shall be in 

accordance with the following table: 

Table 14: Maximum Permitted Ground Vibration Levels 

Item 

Type of Building or Structure 

Peak Particle Velocity 

(mm/s) 

1 Historical buildings monument and buildings of special 

value or significance. 

2 Houses and low rise residential buildings, Commercial 

buildings not included in (3) below 

3 Commercial and industrial buildings or structures of 

reinforced concrete or steel construction 

2 

10 

25 

The above limits are relevant to damage only. With regards to human sensitivity the Contractor will determine 

maximum permitted ground vibrations in consultation with the affected owner or occupier. The proposed 

noise and vibration arising from the TEM earthworks will be managed and mitigated to have a less than minor 

effect on the surrounding environment. 

9.2.3 Dust 

The suppression of the dust over the site will be an ongoing task throughout the duration of the earthworks. 

Where practicable, early establishment of vegetation over exposed areas will be completed, particularly if sites 

need to be left for settlement. Other means of suppressing dust may include the use of water carts, sprinklers 

and dust suppressants. 

Before commencing work on site the Contractor will be required to prepare a Dust Suppression Plan (DSP) to 

the approval of EBOP. The DSP and its implementation shall satisfy all Resource Consent Conditions and 

include as a minimum: 






• Information on the proposed work programme; 

• Identification of likely sources of dust; 

• Management procedures that will minimise dust emissions; 

• Plant, equipment or other measures that will be used to control dust; 

• Identify the contact person responsible for dust management; 

• Proposed source of water and expected quantities required. 

• The Contractor shall keep on site a complaint register and clearly record all complaints they receive about 

dust nuisance. The register shall record: 

• The date, time and duration of the dust emission leading to the complaint; 

• The location of the complaint and source of dust emission; 

• Weather conditions, wind conditions and direction at the site when the event occurred 

• The corrective action undertaken; 

• Persons notified, and when, of the corrective action. 

The proposed dust arising from the TEM earthworks will be managed and mitigated to have a less than minor 

effect on the surrounding environment. 

9.2.4 Archaeological Effects from Construction 

The proposed construction corridor for the Tauranga Eastern Motorway between Te Maunga and Domain Road 

will not impact on previously recorded archaeological sites. No previously unrecorded archaeological sites 

where identified during the April 2008 archaeological survey. In any area where many archaeological sites 

have been recorded in the general vicinity it is possible that unrecorded subsurface remains may be exposed 

during ground disturbance associated with the project. Should sites be located in the course of road 

construction, an Authority from the NZHPT would be required before work could proceed. 

An Authority will be applied for in advance of earthworks as a precaution so that delays can be avoided. This 

Authority will cover areas that are not already covered in the NZHPT Authority associated with the TEM 

alignment works, namely; within the Mangatawa Flood Bypass Area located between Mangatawa Lane and Tip 

Lane. If sites are present they will be recorded and if necessary investigated under the conditions of the 

Authority from the NZHPT, to mitigate their destruction in the course of road construction. 






9.2.5 Hazardous Substances/Contamination/Probability of Risk 

The major risk from hazardous substances is where the contaminant can enter a water way during 

construction. 

The operation of plant and machinery in this environment has the potential to result in adverse effects on the 

environment through things such as accidental spills of fuels and chemicals. Before beginning works on any 

site, the Contractor prepare and implement an Environmental Safety Plan (ESP) that shows what measures will 

be taken to protect the environment from accidental spills. 

Further, the Contractor must have in place all contingency and emergency plans and procedures before 

starting work. 

All machinery and plant shall be operated in a manner that ensures spillage of fuel, oil and similar 

contaminants are prevented during refuelling, machinery servicing and maintenance. Refuelling and 

lubrication activities shall be carried out so that any spillage can be contained and not enter any stream, 

tributary or wetland. 

The risks associated with contamination from hazardous substances arising from the TEM earthworks will be 

managed and mitigated to have a less than minor effect on the surrounding environment. 

9.3 Assessment of Stormwater and Earthworks Cultural Aspects 

A record of consultation is included in this report and details the concerns expressed by Hapu and Iwi in 

regard to this proposal. 

In summary the issues raised during Tangata Whenua consultation include: 

• Water quality of the stormwater discharge 

• Flooding effects 

• Kairua Road flooding 

• The significance of harbour shellfish 

• Long term effects of stormwater run off sedimentation contamination and effect on Tauranga Harbour 

• White baiting on the lower drain and opportunity to encourage the fishery 

• Protection of the eel fishery 

• Mangatawa catchment land flooding residence times 






• Species of vegetation used in swales 

• Source of the fill for earth works 

• Volume of water in the Mangatawa Drain 

Mitigation measures addressing these issues are as follows: 

i. Planting strategies for the TEM swales will include wetland vegetation appropriate for the swale 

environments which will assist in the treatment of the stormwater prior to discharge to the receiving 

watercourses. 

ii. 

Planting within the riparian margins of the Mangatawa Drain will aim to enhance the habitats where 

practicable through native, non-invasive species. 

iii. 

TEM TWAG has prepared a detailed earthworks protocol which will apply to this area as well as the 

remainder of the project site. 

iv. 

Modelling undertaken in the development of the stormwater management system design has 

incorporated flood levels adjusted for climate change to ensure appropriate treatment and controlled 

discharge rates to the harbour. 

v. Maintenance of the TEM swales will not utilise sprays and vegetation will be replaced as required (likely 

to be approximately every 20 years). An asset management plan will be maintained by NZTA for the 

ongoing maintenance of the system. 

vi. 

Appropriate measures will be taken to ensure that the TEM and TCC culverts are designed to ensure that 

passage for fish throughout the existing watercourses is maintained and works in the Mangatawa Drain 

will be undertaken outside of the spawning periods as defined the by the RWLP. It is not proposed that 

fish passage be provided from the storm water treatment wetland or the Mangatawa drain up into the 

Maranui Swale as these areas are not ecologically significant. 

vii. The treatment provided by roadside swales and the enlarged TCC treatment pond will reduce the 

contaminants entering the Mangatawa Drain and Rangataua Bay from existing developments and the 

TEM developments. 

The potential of the Mangatawa drain for food gathering purposes was raised during the consultation as 

important to Nga Potiki and other users of the drain. Preventing the stormwater from the TEM alignment from 

entering the upper and lower Mangatawa Drain, and the proposed recreation and access improvements on the 

Lower Mangatawa Drain will provide positive benefits to the users of the lower waterway in these aspects. 

NZTA is continuing dialogue with Nga Potiki and all other Tangata Whenua groups through the TEM TWAG as 

the project proceeds into final contract design and construction. 

These actions reduce the effects of the proposal to a no more than minor level. 






10. Statutory Assessment 

10.1 RMA 1991 

Part II Section 5 Purpose 

1. The purpose of this Act is to promote the sustainable management of natural and physical resources. 

2. In this Act, “sustainable management” means managing the use, development, and protection of natural 

and physical resources in a way, or at a rate, which enables people and communities to provide for their 

social, economic, and cultural wellbeing and for their health and safety while – 

• Sustaining the potential of natural and physical resources (excluding minerals) to meet the reasonably 

foreseeable needs of future generations; and 

• Safeguarding the life-supporting capacity of air, water, soil and ecosystems; and 

• Avoiding, remedying, or mitigating any adverse effects of activities on the environment. 

Comment 

The sustainable management of the State highway physical resource has been considered alongside the 

potential environmental effects of the construction an operation of the highway. The proposed motorway 

enables the community to provide for its current and future social and economic well being, improves the 

health and safety of the current users of the existing SH 2 while avoiding remedying and mitigating the 

potential harmful effects on the life supporting capacity of air, water, soil and ecosystems. 

The effect of this proposed activity will also reduce the incidences of spills across the motorway providing 

greater route security for the State highway. It will also reduce the incidences of water entering and flooding 

the Maranui and Wairakei Catchments reducing the effects of surface water from the Papamoa Hills. The 

mitigation measures proposed reduce any potential effects to a less than minor level thereby achieving the 

objectives of the RMA listed above. 

The proposed works are in accordance with those matters listed in Section 5 of the RMA and will enhance the 

ability for communities to provide for their social and economic wellbeing through providing a safer and more 

efficient strategic transport route. 

Section 6 Matters of National Importance 

The following matters of national importance are considered relevant to the applications: 






(a) The preservation of the natural character of the coastal environment (including the coastal marine 

area), wetlands, and lakes and rivers and their margins, and the protection of them from inappropriate 

subdivision, use, and development: 

(c) The protection of areas of significant indigenous vegetation and significant habitats of indigenous 

fauna: 

(e) The relationship of maori and their culture and traditions with their ancestral lands, water sites, waahi 

tapu and other taonga. 

Comment 

The stormwater management system and construction management regimes will avoid, remedy and mitigate 

effects and thereby preserve the natural character of the downstream coastal environment. The Special 

Ecological Area listed in the District Plan will be continued to be protected by enlarging the treatment 

capabilities of the existing stormwater treatment facility thereby maintaining protection of the only significant 

indigenous vegetation on the project area. The proposed Mangatawa Flood Bypass will bypass the SES 13, 

minimising potential effects from flood discharges at this location. Archaeological and cultural protocols 

support the relationship of maori and their culture and traditions with the lands, water, sites, waahi tapu and 

other taonga. 

Section 7 Other Matters 

In achieving the purpose of this Act, all persons exercising functions and powers under it, in relation to 

managing the use, development, and protection of natural and physical resources, shall have particular regard 

to— 

(a) Kaitiakitanga: 

aa) The ethic of stewardship: 

(b) The efficient use and development of natural and physical resources: 

(ba) the efficiency of the end use of energy: 

(c) The maintenance and enhancement of amenity values: 

(f) Maintenance and enhancement of the quality of the environment: 

(i) the effects of climate change: 

Comment 

This proposal meets the parameters of Section 7 listed above by providing for the use, development, and 

protection of natural and physical resources. The proposal was separated from the TEM project because of the 

complex way the stormwater was required to be managed in this area. Constraining elements of the proposal 

included the large urban areas in the Wairakei, Maranui and Arataki catchments, the infrastructural networks in 






the project area and the nearby Marae of Nga Potiki. NZTA has undertaken a lengthy and thorough 

consultation process during the project history. The stewardship ethic and an understanding of Kaitiakitanga 

are present in the project through NZTA’s own organisational values and in its consultation with hapu affected 

by the proposal. This is seen in restriction of works in the Lower Mangatawa Drain to help to protect the 

whitebait and eel fisheries identified by Nga Potiki and other users of the waterway as important. 

In this area there is also opportunity for restoration of the lower Mangatawa Drain and the opportunity for 

newly created recreational areas adjacent to the drain increase the potential amenity of the area. 

The stormwater treatment design and mitigation provisions reduce the contaminants entering the water way 

and highlight NZTA’s desire to maintain and enhance the quality of the environment. 

Furthermore, in providing for an easy free-flowing motorway access from Paengaroa to the Port of Tauranga 

and surrounding environs, there will be more efficient use of energy used in transportation and reduced 

greenhouse gas emissions in comparison to the current State highway. 

Section 8 Treaty of Waitangi 

Section 8 states that: 

In achieving the purpose of this Act, all persons exercising functions and powers under it, in relation to 

managing the use, development, and protection of natural and physical resources, shall take into account the 

Principals of the Treaty of Waitangi (Te Tiriti o Waitangi). 

Comment 

The process of consultation undertaken by NZTA has been extensive and inclusive. Not only in the current 

resource consent processes but in the original Designation process the project has been discussed with 

representatives from Iwi and hapu from the area. The NZTA has attempted to undertake a partnership 

approach to the Project and has facilitated the creation of the TEM TWAG as a forum for the resolution of 

construction issues. 

District Council – Land Use Consent 

Section 104D Particular restrictions for non-complying activities 

This section quoted below relates to the consideration of the district land use consent for earthworks adjacent 

to the SES13. 

(1) Despite any decision made for the purpose of section 93 in relation to minor effects, a consent authority 

may grant a resource consent for a non-complying activity only if it is satisfied that either— 

(a) the adverse effects of the activity on the environment (other than any effect to which section 

104(3)(b) applies) will be minor; or 

(b) the application is for an activity that will not be contrary to the objectives and policies of— 

(i) the relevant plan, if there is a plan but no proposed plan in respect of the activity; or 






(ii) the relevant proposed plan, if there is a proposed plan but no relevant plan in respect of the 

activity; or 

(iii) both the relevant plan and the relevant proposed plan, if there is both a plan and a proposed plan 

in respect of the activity. 

(2) To avoid doubt, section 104(2) applies to the determination of an application for a non-complying activity. 

Comment 

In relation to the District Plan the non complying element of the proposal relates to the earthworks and 

removal of vegetation required by the redesign of the stormwater treatment wetland. The wetland needs to be 

redesigned to accommodate stormwater generated from the TEM, the future developed Maranui residential 

area, the proposed Truman Lane industrial area and some of the Arataki catchment. This will require 

earthworks significantly greater than the threshold set adjacent to the SES. 

These activities will provide better environmental outcomes for the SES by improving water quality in the 

Harbour and reducing the potential for sediment to enter the Harbour. 

To reduce the likelihood of effects on the SES, the earthworks activity will be undertaken in accordance with 

the example Erosion and Sediment Control Plan that is submitted as part of this consent. The plan provides 

guidelines and environmental criteria that the contractor will be required to meet to mitigate the potential 

effects of this activity to a less than minor level. Compliance with these guidelines will be embedded in the 

contracting documents being the Principals Requirements. 

Removal of vegetation in the Stormwater Treatment Wetland is required to redesign the pond to achieve the 

ARC TP10 treatment level for stormwater. The design however has retained existing vegetation as much as 

practicable but some removal is expected. The wetland will be re-vegetated with appropriate species to 

mitigate some of the lost vegetation. Given the temporary nature of this loss and NZTA’s and TCC’s 

undertaking to restore where possible, the effects of this activity are considered to be less than minor. 

Commentary on the objectives and policies of the district plan regarding the non complying activity is detailed 

in section 10.6 

10.2 Bay of Plenty Regional Policy Statement (RPS) 

These resource consent applications for earthworks, water take, structures and stormwater discharge do not 

challenge the intent the objectives and policies listed in the RPS, in particular: 

Maori Culture and Traditions -Objective 5.3.2(a): 

Recognition of and provision for the relationship of Maori and their culture and traditions with their ancestral 

lands, water, sites, waahi tapu, and other taonga. 






Comment 

NZTA’s representatives have undertaken extensive consultation during the TEM process, starting with the 

designation phase and continuing through to the current phase. Throughout this process, NZTA staff and 

consultants have been aware of the historical and cultural importance of ancestral lands, water, sites, waahi 

tapu, and other taonga to iwi and hapu affected by the Project. 

As part of this application Tauranga City Council has taken part in all consultation, attended meetings and hui 

to answer questions and queries regarding the Mangatawa Floodway proposal. NZTA and TCC have developed 

a relationship with affected hapu and iwi and throughout the Project have listened, discussed and incorporated 

iwi and hapu interests in the project. An example of this process is in the preparation of the protocol and the 

intention to provide training for monitoring of earthworks for the project and the restriction of works in the 

lower Mangatawa Drain as much as possible. 

Water Quality -Objective 8.3.1(a): 

Water quality is maintained, and where practicable enhanced, to a level sufficient to safeguard aquatic life, to 

sustain the potential for water resources to be used and developed to meet existing and reasonably 

foreseeable future needs, and to provide for the protection of aesthetic or cultural values associated with 

water. 

Comment 

Water quality is maintained by the extensive use of wet swales along the proposed motorway and the swales 

will be designed using the ARC TP10 as the level of treatment required. The TEM alignment will drain to a 

surrounding network of swales though catch pits and pipes removing the current roadway water from the 

upper Mangatawa Drain approx ch 7900. The TEM from this point drains directly into the Maranui swale and 

will be treated by the enlargement of the Tauranga City Council wetland to meet this objective. 

Land- Objective 6.3.1(a): 

The adoption of sustainable land use and management practices. 

Comment 

The stormwater management system will enable the continuance of the rural and urban activities alongside the 

operation of the new motorway. The floodway is designed to provide flood protection to residentially zoned 

land in Papamoa. The sustainable land use practices laid out in the District Plan for residential areas require 

this basic protection. 

In addition the TEM Construction Management Plans will be crucial to ensuring that the construction methods 

will support the life-supporting capacity of soil and protect the quality of water in the farm drains and local 

streams and rivers. 

Contaminated Sites -Objective 12.3.4(a): 

The significant adverse effects of site contamination are avoided, remedied or mitigated. 






Comment 

A desk top study has been conducted by Beca for contamination from previous land-use practice. It is 

intended that provision for a more detailed contaminated sites study be included in the TEM Principal’s. 

Requirements and undertaken during the construction phase of the Project. Specific conditions requiring 

further investigations and measures relating to contaminated land in this proposal will be included. 

10.3 Operative Regional Water and Land Plan (RWLP) – 1 st December 2008 

The RWLP provides for the integration of the management of land and water resources in the Bay of Plenty 

Region. There are a number of Objectives, Policies and Rules contained in the RWLP which are relevant to 

these resource consents. These are briefly discussed in the following paragraphs and they are quoted for 

completeness in Appendix 14. 

Chapter 2.0 - Kaitiakitanga 

The RWLP contains a number of provisions relating to Kaitiakitanga, specifically in Objective 4 and Objective 5 

and Policies 14, 15, 17, 18 and 20 and Policy 42. 

As outlined extensive consultation with Tangata Whenua has taken place as part of these consents in addition 

to the consultation undertaken during the designation phase of the Project as described in paragraph 16 

above. Policy 42 is referred to in paragraph 128 below. 

Chapter 3.0 – The Integrated Management of Land and Water 

The RWLP contains a number of provisions relating to the integrated management of land and water, 

specifically in Objectives 8, 10, 13, 14, 17, 19, 22 and cross-reference to Objectives 15.3.1(a) and 16.3.1(a). 

The integrated management of land and water incorporates the values of stewardship of natural resources and 

protecting the life supporting capacity of soils, water and ecosystems, management of riparian margins, and 

the protection of vulnerable areas from erosion. This project maintains the cultural, ecological, amenity, 

natural character and landscape values of the site through careful management and the extensive consultation 

through out the entire process up to these consents. 

With regard to the quality of the water derived from the motorway, the treatment proposed for the stormwater 

involves the best practicable option and will be in accordance with industry standard approaches. It will be an 

improvement on the existing stormwater discharge with respect to the TEM discharge to the Mangatawa drain 

and will be appropriate for discharge to the Tauranga Harbour. 

The ecological assessment undertaken by Bioresearches does not highlight any ecologically sensitive areas or 

species that the proposed activities will significantly affect. While there is Special Ecological Site adjacent to 

proposed works special care has been taken to avoid, remedy or mitigate effects on this area. 

The Maranui swale and outlet to Rangataua Bay, work already undertaken by TCC, provide significant reduction 

in the flood risk to the residential areas of Papamoa and the potential effects from flooding. 






In addition, the mitigation proposed to control the temporary effects of the earthworks on the environment, as 

well as the attenuation and treatment proposed to manage the effect of the stormwater, will be consistent with 

Objectives 10, 17 and 19. The Project will also provide for the beneficial effects of providing a key 

transportation corridor. 

Chapter 4.0 – Discharges to Water and Land 

Discharges of Contaminants or Water to Water, and Discharges of Contaminants to Land and 4.2 Discharge of 

Stormwater. 

Provisions relating to discharges to land and water are contained in the RWLP in Objectives 23, 26, 31, 32, 34 

and Policies 38, 39, 42, 50, 51, 54, 56 and 57. 

The proposed stormwater management philosophy for the TEM is to maintain or enhance the quality of 

stormwater prior to its discharge to the local streams and rivers. Management of stormwater related to 

flooding and treatment were major concerns of surrounding landowners, hapu and most of the stakeholders 

during the consultation process. NZTA has undertaken to meet the ARC TP10 level of treatment for road way 

derived stormwater while mitigating the risk of flooding through attenuation of the stormwater created by the 

motorway. In this way, the Project addresses the concerns of the submitters and affected parties in the 

Project. 

The Mangatawa catchment is predominantly rural and the runoff from this land is likely to contain typical rural 

nutrients and contaminants. Treatment of this runoff is not part of this project and will continue as it does 

currently as the land management practices of this catchment are beyond this projects ability to practically 

control. 

With regard to the accidental spillage of hazardous substances during TEM construction, this will be managed 

through the Environmental Safety Plan which will show what measures will be taken to protect the environment 

from accidental spills. It is intended that these measures will be in place before construction located 

appropriately. 

Chapter 6.0 - Beds of Rivers, Streams, Lakes and Wetlands 

Activities in the Beds of Rivers, Lakes and Streams 

Objectives 55, 57, 58, 59, 73, 74 and Policies 98 to 102, 133, 134 of the RWLP relate to the beds of rivers, 

streams, lakes and wetlands. 

The construction works required in the Upper Mangatawa Drain will have a temporary effect on the ecological 

value of the drain. These works require the drain bed to be lowered through excavation; coffer dams to protect 

the placement of gabion baskets and reno mattresses; and protection of the flow path from the construction of 

the strengthening embankment at the rail bridge. The works will only affect the ecological value of the stream 

for short periods if managed appropriately. 

The principals of the philosophy to mitigate these effects are laid down in the example Erosion and Sediment 

Control Plan in Appendix 13. The drain itself is a highly mobile environment with a sandy bottom and the flora 

and fauna found in this drain will be well used to high levels of sediments from high rain fall events. 






However the fundamental approach for controlling the effects of sedimentation will be to restrict the duration 

of works in the drain to an absolute minimum as to avoid fish spawning and migration periods and reduce the 

impacts of sediment in the drain. 

The re-vegetation of the Mangatawa Drain will help to preserve the preserve the ecological values of the 

receiving drains and rivers and flora and fauna of this drain should be able to establish quickly after 

construction has been completed. 

10.4 Bay of Plenty Regional Air Plan 

The discharge of dust from the site is to meet the permitted activity provisions of Rule 17(e). 

10.5 Regional Coastal Environment Plan Coastal July 2003 

Tauranga Harbour and surrounding lands form the traditional rohe of Ngaiterangi Iwi known as “Mai i nga Kuri 

a Wharei ki Wairakei.” Hapu of Ngaiterangi maintains strong local communities which are dependent on 

maintenance of the life-supporting capacity of the harbour and surrounding land. Maintenance of kaimoana 

and coastal water quality is particularly important. Tauranga Moana is rich in cultural heritage sites for 

Ngaiterangi and other iwi. Many of the sites are of significance to Ngaiterangi te Iwi, while others are 

significant to specific hapu. In addition to the harbour itself the following places have particular significance 

for Ngaiterangi: 

• Te Tahuna o Rangataua (Rangataua Bay) 

There are no rules pertaining to storm water discharge into an ecological area, however Rule 9.2.4(a) of the 

Regional Coastal Plan applies. The discharge into the CMA will be a permitted activity subject to the following 

conditions. If these conditions can not be met the discharge becomes a discretionary activity. 

9.2.4(a) The discharge of stormwater to the coastal marine area is a permitted activity provided that: 

• the suspended solids concentration of the water discharged does not exceed 150 g.m-3; and 

• the water discharged is substantially free of grease, oil, scums and foam; and 

• the maximum discharge does not exceed 80 litres per second for a 20% AEP storm event (5 year return 

period storm). 

9.2.4(b) Except as expressly provided for or prohibited by other rules to this plan, any discharge is a 

discretionary activity. 






Comments 

This assessment shows that the TEM project can treat the water generated by the alignment reducing the levels 

of sediment, copper and zinc to less than existing levels. 

10.6 Tauranga District Plan 

4.2.2 Objective: To Sustain Natural Resources by Protecting the Functioning and Integrity of Ecosystems 

4.2.2.3 Policy: Location of Activities 

Use and development should avoid locating in the coastal environment where the natural character remains 

intact. Activities should seek to locate where natural character has already been compromised and adverse 

effects of activities can more readily be avoided, remedied or mitigated. 

4.2.2.5 Policy: Indigenous Flora and Fauna 

It should be recognised that intact areas of indigenous flora and fauna are underrepresented in the District, 

and use and development should provide for their maintenance and enhancement. 

Comments 

The stormwater treatment for urban and TEM purposes require the enlargement of an existing manmade 

wetland. The wetland provides the best opportunity to avoid large scale effects on ecosystems from the 

operation of the TEM and urban run off. Locating the wetland elsewhere would possibly require further land 

take and increase the effect of the proposal on private and public land holders. Locating the TEM treatment 

facility within this site represented the best approach to minimise the effects on the SES site. 

The wetland will also be replanted increasing the areas of indigenous flora and fauna on the site 

4.2.3 Objective: Protecting Special Ecological Sites 

To protect in their natural state and sustainably manage all significant habitats of indigenous flora and fauna 

of the District. 

4.2.3.2 Policy: Special Ecological Sites 

Subdivision, use and development within or adjacent to sites identified in Appendix 14A: Special Ecological Site 

Register or within or adjacent to other areas of significant indigenous vegetation and significant habitats of 

indigenous fauna, as defined by Policy 4.2.3.3, must be carried out in a way that does not result in a reduction 

in the health, viability or ecological values of those sites. 






Comment 

The health and viability of the Special Ecological Site 13 will be protected in several ways. The non-complying 

activity conditions in the plan relate to the removal of vegetation and earthworks in the vicinity of the site. The 

removal of vegetation will be avoided where practicable but some indigenous vegetation may be lost in areas 

required for stormwater control. The over all design of the pond has preserved as much of the vegetation as 

possible and replanting and restoration will be undertaken to restore vegetation cover. 

A Construction Management Plan and Erosion and Sediment Control Plan will be produced by the contractor 

responsible for the construction of the wetland. These measures will reduce further the potential for the 

construction of the wetland to have an effect on the SES 13. Overall the effect on the SES will be no more than 

minor. 

4.3.1 Objective: Water Quality and Quantity - Stormwater and Wastewater 

4.3.1.1 Policy: Stormwater Management 

Subdivision, use and development should not adversely affect the ability of Greenbelt Zones and other 

substantially vegetated areas to effectively filter stormwater run-off from adjacent catchment areas. 

4.3.1.5 Policy: Stormwater Discharges in the Coastal Environment 

The loss of natural character of the coastal environment from the discharge of stormwater across the foreshore 

or through dunes and the presence of stormwater disposal structures in the coastal environment, should be 

avoided or, where avoidance is not practicable, substantially mitigated. Particular regard should be had to the 

visual effects of piping, culverts and physical works associated with discharge structures and activities. 

4.3.1.6 Policy: Stormwater Discharges to the Coastal Environment 

Land-use activities that involve discharge of stormwater to the coastal environment, wetlands and rivers 

should include measures to avoid, remedy, or mitigate any adverse effects of heavy metals, greases, 

suspended solids and other contaminants on the receiving waters, and should include measures to mitigate 

any adverse effects of the energy of the discharge on receiving waters. 

4.3.1.7 Policy: Stormwater and Wastewater Quality 

Land-use activities should not discharge any contaminant or water containing any contaminants into a 

stormwater or wastewater system or on to land that will result in a cumulative adverse affect on the quality of 

the District’s soil or groundwater systems. 

Comment 

This proposal seeks to increase the volume of water discharging from the Stormwater Treatment Wetland into 

Special Ecological Site 13. These increases arise from the inclusion of the future developed Maranui catchment 

stormwater in the wetland, the future developed industrial land owned by MPBI at Truman lane and at 

Mangatawa and the TEM derived stormwater up to the 1% AEP level. It provides necessary treatment of the 

water from the Papamoa, Wairakei, Mangatawa (some) catchments and the TEM alignment through swales and 






the reconfigured wetland. This will improve the over all quality of the water discharging to the harbour 

through the Special Ecological Site 13. It also will result in increase in peak flow volume at Mangatawa Drain. 

The extra volume (3.9 cubic meters to 13.6 cubic meters) discharging from the wetland will be mitigated by 

providing an enlarged discharge structure (from existing) to protect from erosion and scour. These measures 

will result in the project having a no more than minor effect on the environment. 

7.4.1 Objective: Transportation Safety and Efficiency 

To maintain safety and efficiency in the movement of people and goods on the District’s road, rail, air and 

shipping networks. 

7.4.1.1 Policy: Design and Use of Roads New roads and activities within the road reserve must be designed, 

located and constructed in a way that ensures: 

(a) Safe movement of pedestrians, cyclists and vehicles around the District 

(b) Physical integration with other transport routes, where appropriate 

(c) Avoidance, remediation or mitigation of the impacts of noise and traffic movement on the amenity of 

surrounding sites, particularly from strategic or arterial routes. 

Comment 

The objective of maintaining an improving safety and efficiency is an integral part of the design of the TEM. 

The project provides a safe movement for vehicles around this district (and other districts), integrating with 

other transport routes and mitigating the transport related effects of the alignment to a no more than minor 

level. TEM is a key component of the Tauranga Eastern Transport Corridor. The Tauranga Eastern Corridor is 

the transportation network required to service the existing and predicted inter-regional traffic as well as the 

urban growth of Papamoa East. Papamoa East is the largest growth area of the Western Bay of Plenty subregional 

SmartGrowth strategy. 

This project will result in positive benefits to the Tauranga District and the safe and efficient operation of the 

transport network. 






10.7 Wairakei Urban Development Comprehensive Stormwater Consent 

The application for the Papamoa catchment was lodged with Environment BOP in 2006 and is being processed 

in conjunction with the Papamoa East (Wairakei) Plan Change. The consent has been granted and appeals are 

largely resolved. The application has been required to consider not only the current urban area but the full 

urbanization of the Wairakei and Te Tumu areas over the next 50 years. 

The key issue has been flood management in a catchment with a limited outlet to the ocean. The long term 

proposal is a high level outlet to the Kaituna River to be constructed in conjunction with the commencement of 

the development of the Te Tumu area around 2021. In order to manage the flooding of the existing rural land 

in Te Tumu in the interim, pumping excess water to the Kaituna is proposed. 

This TEM proposal integrates flood levels set in the Wairakei consent in terms of stormwater discharge. 






11. Conclusion 

The complexity of stormwater management in this section of the TEM alignment is a consequence of the way 

that stormwater behaves across the three catchments in the project baring area, Wairakei, Maranui and 

Mangatawa. The May 2005 floods highlighted the need for flood management in the area and Tauranga City 

Council has undertaken significant works to address this issue (e.g. the Maranui Swale). 

In this assessment of effects it is clear that effects of the earthworks, stormwater management, are no more 

than minor providing that the mitigation measures are implemented as design principles and through 

avoiding, remedying and mitigating the potential adverse effects of this proposal. 

A key part of the management and mitigation of effects is NZTA’s decision to embed the environmental 

bottom lines into the contract documentation called the “Principals Requirements”. 

11.1 Mangatawa Flood Bypass 

A key objective of protecting urban areas from floods is to reduce the volume of water entering these 

catchments and to provide a better flow path for flood waters to discharge to the sea. 

The spills threaten the safe and efficient operation of the State highway network and the desire by NZTA is to 

reduce or restrict completely the number of spills across the State highway. However when allowances for 

climate change are made, completely reducing spills is technically constrained by environmental factors, is 

costly, as well as potentially creating significant effects on the environment. Therefore a more moderate 

approach was chosen. 

The proposed option reflects a sustainable management approach by balancing the need to protect the urban 

areas in Papamoa and Sate highway infrastructure; and avoiding significant environmental effects on the 

Mangatawa drain and lands surrounding the drain. 

11.2 TEM Stormwater Management 

The methodology will provide a higher level of treatment than existing currently and will reduce the levels of 

sediment, copper and zinc to less than is currently experienced providing benefits to water quality in 

Rangataua Bay. 

The effect from stormwater relates to the management of road way derived stormwater and its impact on the 

surrounding catchment and the effects from the flood by pass activities. The effects can be generally described 

as flood risk, treatment and conveyance of stormwater. The stormwater system is designed to achieve 100% 

attenuation in a 1% AEP event. This level of attenuation is necessary across the entire alignment because of the 

sensitivity of the receiving environments in the Special Ecological Site 13 and all three catchments. 






The effects stormwater activities can be considered to be less than minor because of the adoption of the core 

design criteria of TP 10 and 100% attenuation in the TEM stormwater management system. 

11.3 Earthworks 

The construction of these stormwater treatment and control devices will create temporary effects on water 

quality, noise dust and vegetation clearance. Perhaps most significant is the potential effects of sedimentation 

arising from erosion and scour during construction. This effect will be managed by adopting erosion and 

sediment control measures as defined in the Bay of Plenty Regional Council’s Erosion and Sediment Control 

Guidelines for Land Disturbing Activities (2001) and shown as example in Appendix 13. Fundamentally the 

best approach will be to: restrict the duration of works in the drain to an absolute minimum as to avoid fish 

spawning and migration periods and reduce the impacts of sediment in the drain; re-vegetate the Mangatawa 

Drain to preserve the ecological values of the receiving drains and adopt sediment control measures where 

possible and practicable. These measures will be embedded in Construction Management Plans and Erosion 

and Sediment Control Plans that will be submitted to the Regional Council by the contractor for approval 

before construction. 

The effects from the earthworks activity can be considered no more than minor because of their temporary 

nature. Although a long duration period is needed the activity is planned to be completed within a 5-year time 

frame. 

11.4 Statutory Conclusion 

This proposal is considered to be consistent with the Part II matters and meets the purposes of the Resource 

Management Act. Consideration and operation of the effects of these activities can be sufficiently avoided, 

remedied and or mitigated. 




APPENDIX 1 - 

Drawing 3932036 ck301Rev C

APPENDIX 2 - 

Extract from Tauranga District Plan: 

Special Ecological Site 13

APPENDIX 3 - 

Drawing 3932036 ck119 Rev F

APPENDIX 4 - 

Drawings 3932036 ck073 Rev G, 

ck074 Rev E, ck 075 Rev F

APPENDIX 5 - 

Bioresearches Report: Ecological 

Features of some Habitats within 

Rangataua Bay Catchment

APPENDIX 6 - 

Ngaiterangi Cultural Impact 

Assessment

APPENDIX 7 - 

Archaeological Assessment: Te 

Maunga to Domain Road, 

Archaeology BOP

ARCHAEOLOGICAL SURVEY 

AND ASSESSMENT OF EFFECTS 

PROPOSED 

TAURANGA EASTERN ARTERIAL 

CONSTRUCTION CORRIDOR 

TE MAUNGA TO DOMAIN ROAD 

Prepared by 

KEN PHILLIPS (MA HONS) 

For 

BECA PLANNING 

APRIL 2008 

ARCHAEOLOGY B.O.P. 

HERITAGE CONSULTANTS 

P O BOX 855 

WHAKATANE 

Phone: 07 307 9455 

Mobile: 027 276 9919 

Email: KJS.Phillips@xtra.co.nz

ARCHAEOLOGY B.O.P. 

HERITAGE CONSULTANTS 

2 March 2009 

Michael Seabourne 

Senior Planner 

Beca 

P O Box 903 

TAURANGA 

Re: Archaeologist issues – Mangatawa Flood Bypass Area 

Dear Sir 

I provide the following information regarding archaeological issues within the Mangatawa 

Flood Bypass Area located between Mangatawa Lane and Tip Lane. 

There are no previously recorded archaeological sites and no unrecorded archaeological sites 

were within land affected by the Mangatawa Flood Bypass Area. However prehistoric 

occupation on the eastern edge of the wetland and on raised ground on the eastern side of 

Mangatawa Lane was likely to have been extensive. The area was a poorly drained wetland 

in prehistory and would have been a source of construction materials such as raupo and food 

such as birds and eels. The collection of such resources rarely leaves an archaeological 

record, however, swamp and wetland environments often contain artifacts made form 

organic materials such as wood and flax as the anaerobic conditions of wetlands provide an 

environment that can preserve buried organic materials that rarely survive elsewhere. Many 

wooden and organic artifact assemblages have been recovered from wetland sites throughout 

the Bay of Plenty. Wetland areas within the construction corridor and the Mangatawa Flood 

Bypass Area have the potential to contain such artefacts especially given the high 

concentration of archaeological sites on the surrounding hill country and dune plain. 

I have amended my report on the proposed Tauranga Eastern Motorway construction 

corridor between Te Maunga and Domain Road (April 2008) to include this area. 

Yours faithfully 

Ken Phillips 

ARCHAEOLOGY B.O.P. HERITAGE CONSULTANTS P O BOX 855, WHAKATANE 

MOBILE: 027 276 9919 EMAIL: KJS.PHILLIPS@XTRA.CO.NZ

1 

CONTENTS 

INTRODUCTION 2 

Project Background 2 

Methodology 3 

PHYSICAL LANDSCAPE 3 

ARCHAEOLOGICAL LANDSCAPE 4 

Previous Archaeological Research 4 

Recorded Archaeological Sites 4 

U14/1708 & 1709 Midden 5 

U14/1842 Artifact Find spot 7 

U14/1843 Oven Stones 7 

U14/2309 Artifact Find spot 9 

U14/2903 & 2904 Midden 9 

Hungahunga & Toroa 10 

Unrecorded Archaeological Sites 11 

APRIL 2008 ARCHAEOLOGICAL SURVEY 12 

Survey Results 12 

DISCUSSION & CONCLUSION 13 

Summary of Results 13 

Archaeological Significance 13 

General Considerations 13 

Effects of Proposal 13 

Historic Places Act 14 

RECOMMENDATIONS 15 

REFERENCES 15

2 

INTRODUCTION 

Project Background 

This archaeological survey and report was commissioned by Beca Planning, in order 

to determine if archaeological sites are affected by the proposed Tauranga Eastern 

Motorway construction corridor between Te Maunga and Domain Road including the 

existing State highway 2 Road Reserve and additional land requirements. The 

additional land requirements are presented in Beca Drawing Numbers 3932036 G011 

– G016, G015-G032, G034, G040, G045-G048, G067, G071, G074, G096, G099 and 

G0108. They are collectively referred to as the affected properties or the construction 

corridor in this report. 

An archaeological site, as defined by the Historic Places Act 1993, 2(a)(i) and 2(b) is, 

“any place in New Zealand that was associated with human activity that occurred 

before 1900: and is or may be able through investigation by archaeological methods 

to provide evidence relating to the history of New Zealand”. Archaeological sites 

may not be destroyed damaged or modified except pursuant to an authority granted 

under section 14 of the Historic Places Act. 

This report deals specifically with the identification of physical evidence relating to 

pre 1900 human activity that can be investigated using archaeological methodology. 

An assessment of the cultural significance of an area can only be competently made 

by the affected tangata whenua. It should be noted that an assessment of cultural 

significance might not necessarily correlate with an assessment of archaeological 

significance. 

Figure 1. Part topographic map U14 showing the approximate location of the proposed 

construction corridor and additional land requirements (pink).

3 

Methodology 

Prior to the archaeological survey the records of the New Zealand Archaeological 

Association (NZAA) were consulted to determine whether any archaeological sites 

had previously been recorded on or in the immediate vicinity of the property. Early 

survey plans, aerial photos and archaeological reports relating to the area were also 

reviewed. 

A visual inspection of the affected properties was carried out by Ken Phillips on 9 

April 2008. The survey focused on relocating previously recorded archaeological 

sites and identifying any previously unrecorded sites. The ground surface was 

examined for evidence of former occupation (in the form of shell midden, 

depressions, terracing or other unusual formations within the landscape, or indications 

of 19th century European settlement remains). Subsurface testing based on spade test 

pitting was carried out to determine whether buried archaeological deposits could be 

identified. Particular attention was paid to the elevated spurs crossing the corridor in 

the vicinity of Kairua Road and the subdued back dunes between Te Maunga and 

Mangatawa Lane. Disturbed soils and soil profiles exposed in cuttings were 

examined where encountered for evidence of earlier settlement, and an understanding 

of the local stratigraphy. 

A second visit to the properties was carried out by Ken Phillips and Matire Duncan 

(Ngapotiki representative) on 10 April 2008. 

PHYSICAL LANDSCAPE 

The affected properties are located on the western edge of the Papamoa Dune Plain on 

either side of the State Highway 2 (SH 2) road reserve between the Te Maunga 

roundabout and Domain Road. Land affected by the proposal includes drained 

wetlands, deflated back dunes and low ignimbrite and tephra based spurs. 

Between Te Maunga and Mangatawa Lane the construction corridor follows the 

alignment of a subdued back dune described in 1904 as covered in titree and short 

fern. The dune was used as a principal walking track in prehistory and several track 

alignments have been recorded on old survey plans. 1 Raised land to the west of 

Kairua Road and extending north of Taranaki Lane is described as covered in high 

titree in 1904. Wetlands are variously described as very wet swamp covered in raupo 

and rushes in 1904 2 and flax, manuka and wiwi in 1911 3 . 

Much of the land within the construction corridor has been significantly modified by 

the construction of SH 2 and the East Coast Main Trunk Railway in the first half of 

the 20 th Century while more recent modification including drainage of the wetland 

between Mangatawa and Tip Lanes work and subdivision development on the 

subdued dunes within and immediately north of the proposed construction corridor. 

1 ML 7136 

2 ML 7136 

3 ML 8133

4 

ARCHAEOLOGICAL LANDSCAPE 

Previous Archaeological Research 

Pastoral areas within the proposed construction corridor were included in an 

archaeological survey of the Bay of Plenty carried out by the New Zealand Historic 

Places Trust (NZHPT) in 1983 in reaction to the extensive contouring being carried 

out by the expanding kiwi fruit industry as well as increased road and residential 

development. During this survey seven archaeological sites were identified within 

300m of the proposed construction corridor. 

More recently there have been a number of archaeological surveys carried out in the 

general area for the purposes of resource consent and Historic Places Trust authority 

applications. 

Recorded archaeological sites in the immediate vicinity of the construction corridor 

were inspected or current site information reviewed during the NZAA Site Record 

Update Scheme carried out in Tauranga in 2003 & 2004. 4 

Recorded Archaeological Sites 

There is extensive traditional history and supporting archaeological information 

relating to the pre historic Maori settlement in the area. Defended pa are located on 

the elevated ignimbrite, rhyolite and dacite formations to the southwest and numerous 

occupation sites most often identified by shell midden exposures have been recorded 

along the Papamoa Dune Plain to the north and east. 

Prior to the archaeological survey the records of the NZAA were consulted in order to 

determine if archaeological sites have been recorded within or in the immediate 

vicinity of the construction corridor. Archaeological reports relating to the area were 

also reviewed. 

There are no recorded sites within the proposed construction corridor and 7 recorded 

archaeological sites located within 300m. The 7 sites were recorded during the 1984 

HPT survey of Tauranga District. Three are located on the southern side of the 

railway line and four are located north of SH2 on the subdued back dunes of the 

Papamoa Dune Plain. 

Site No. Site type Easting Northing 

U14/1708 Midden 2795850 6385470 

U14/1709 Midden 2795800 6385400 

U14/ 1842 Artifact Find Spot 2797640 6383540 

U14/1843 Oven Stones 2797710 6383650 

U14/2309 Artifact Find Spot 2799220 6382250 

U14/2903 Midden 2796500 6385100 

U14/2904 Midden 2796400 6385100 

Table 1. Previously recorded archaeological sites within 300 metres of the proposed construction 

corridor. 

4 Phillips 2004

5 

Figure 2. Part topographic map U14 showing the location of recorded archaeological sites in the 

general vicinity of the proposed construction corridor. 

U14/1708 & 1709 Midden 

These two midden sites were recorded in 1996 during an archaeological survey of the 

Papamoa Dune Plain. 5 The sites are described as small subsurface midden deposits 

and are located on the subdued back dune extending south east from the eastern end 

of Gloucester Road and are approximately 200 metres north of the proposed 

construction corridor. The two sites are within 50 metres of each other and probably 

represent components of a single settlement site with possible associated subsurface 

features such as cultivated soils, pits and house sites. The site is situated on the 

seaward side of an old paleochannel described in 1904 as a very wet swamp covered 

in raupo and rushes. 6 

There are few archaeological sites recorded on the back dunes, however, early 20 th 

Century modification of the back dunes particularly between Te Maunga and 

Mangatawa has likely obscured or destroyed archaeological evidence of activity in 

this area. 

5 Fredericksen et al 1995, Gumbley 1997 

6 ML 7136

6 

U14/1708 & 1709 

Figure 3. Cadastral plan and aerial photo showing the location of recorded archaeological sites 

U14/1708 & 1709 in relation to SH2. 

U14/1708 & 1709 

SH2 

Figure 4. Part survey plan ML 7136 produced in 1904 showing the location of U14/1708 & 1709, 

the approximate alignment of SH2 and the intervening wetland.

7 

U14/1842 – Artifact Find Spot 

This site was recorded by Bruce McFadgen during the 1984 survey of Tauranga 

District. According to the NZAA Site Record Form it represents the location of two 

adzes found when a tongue of high ground was bulldozed into the adjacent swamp to 

level the ground for cropping. No photos or sketches of the adzes are available; 

however, they are described by B. McFadgen as ‘moahunter-type’ adzes in the 

possession of Mr T Lennard at the time of recording. Adzes of this type typically date 

to the early prehistoric period of Maori history. 

U14/1843 – Oven Stones 

This site was recorded by Bruce McFadgen during the 1984 survey of Tauranga 

District. According to the NZAA Site Record form the site comprises a concentration 

of burnt fractured stones exposed on the western edge of a tongue of high ground 

within Pt 10 Mangatawa. Ken Phillips inspected the location of the site in June 2002, 

however, the oven stones were no longer visible. 

The identified archaeological sites U14/1842 & 1843 indicate the presence of a pre 

European Maori settlement on the low ridge. A section of the ridge has been quarried 

away during the construction of the railway and SH 2; however, the distal end of the 

ridge on the northern side of SH 2 appears to be relatively unmodified and may 

contain further subsurface archaeological features and or artefacts in the overlying 

volcanic loam soils and within the surrounding wetlands. This includes Pt Lot 1 DP 

34461 affected by the construction corridor. 

Survey plans produced in 1893 (ML 4868) and 1911 (ML 8133) provide a traditional 

place name of Otaimatua for the tongue of raised ground on which U14/1842 & 1843 

are located. 

Figure 5. View looking south east from Bruce road showing the Otaimatua ridge extending 

across SH2.

8 

Figure 6. Part ML 8133 showing Pt 10 Mangatawa within which U14/1842 & 1843 are located. 

U14/1843 

Otaimatua 

Ridge 

U14/1842 

Figure 7. Beca Plan 3932036-G032 showing the land requirement within Pt Lot 1 DP 34461 in 

relation to recorded archaeological sites U14/1842 & 1843 and the approximate extent of 

Otaimatua ridge on which further subsurface archaeology may be present.

9 

U14/2309 Artifact Find Spot 

This site was recorded by Foster during the 1984 NZHPT survey of Tauranga District. 

The site represents the location of an artifact find spot comprising an adze. The adze 

was found by the owner while digging for a water trough on sloping ground just north 

of a swamp. No photo or sketch of the adze is available, however, Foster describes 

the adze as a 2B; a type commonly found on late prehistoric Maori sites. The find 

spot is located on a tongue of raised land extending across SH 2. The distal end of the 

ridge on the northern side of SH 2 has recently been quarried to accommodate the 

new Domain Road SH 2 interchange, however, unmodified areas on the northern side 

of the recent cut may contain further subsurface archaeological features and or 

artefacts in the overlying volcanic loam soils and within the surrounding wetlands. 

The proposed construction corridor in this area is located within the existing modified 

road reserve and it is unlikely that unrecorded archaeology will be affected by the 

current proposal. 

U14/2309 

Figure 8. Cadastral plan and aerial showing location of recorded archaeological sites U14/2309 

in relation to SH2). 

U14/2903 & 2904 Midden 

These two midden sites are located approximately 300m north of the Mangatawa 

Lane SH 2 intersection and are located within a similar environment to U14/1708 & 

1709 on the north bank of the same paleochannel within the Papamoa Dune Plain. 

They are close to an old track that once extended from Karikari point, on the eastern 

side of Rangataua Bay, to Otira on Omanu Beach 7 and may represent a halfway point 

between the coast and Karikari Pa. Mangatawa Lane follows the old track alignment 

south of SH 2 but the northern alignment is no longer visible. The two middens are at 

least 250m north of the proposed construction corridor. 

7 ML 4868

10 

Hungahunga & Toroa 

A further tongue of raised Papamoa ignimbrite extends across the proposed 

construction corridor in the vicinity of the Kairua Road SH2 intersection. The place 

names of Hungahunga and Toroa are provided on survey plan ML 8133 which may 

also indicate further settlement sites and associated archaeological remains in this 

area. The only section of the ridge affected by the proposed construction corridor is 

located within extensively modified railway reserve land on the south-western side of 

SH 2. 

Figure 9. Part survey plan ML 8133 showing the low ridge extending across SH 2 (pink Line) 

and associated place names Otaimatua, Hungahunga, Toroa and Upuhue Pa to the south.

11 

Figure 10. Beca plan 3932036-G034 showing the approximate extent of the Hungahunga / Toroa 

ridge on which subsurface archaeological remains may be present. 

Unrecorded archaeological sites 

The majority of archaeological sites and features in the Bay of Plenty are unrecorded 

and will only be identified following topsoil removal. Recorded archaeological 

features only represent the surface expression of sites and these features generally do 

not represent the full extent of a site. Typically a shell midden exposure in coastal 

Bay of Plenty indicates the presence of more extensive subsurface archaeological 

features. Ploughing and discing have often had little effect on these sites, which 

generally retain high archaeological integrity following such activity. 

It should also be recognised that drained swamp and wetland environments often 

contain artifact rich archaeological sites as the anaerobic environments can preserve 

organic materials that rarely survive elsewhere. Many wooden and organic artifact 

assemblages have been recovered from wetland sites throughout the Bay of Plenty. 

Wetland areas within the construction corridor have the potential to contain such sites 

especially given the high concentration of archaeological sites on the surrounding hill 

country and dune plain. 

Land within the proposed construction corridor that is most likely to contain 

unrecorded subsurface archaeological features include the subdued back dunes on the 

northern side of the alignment between Te Maunga and Mangatawa Lane, the 

ignimbrite and tephra based ridges extending across the alignment in the vicinity of 

Kairua Road and Taranaki Lane and the intervening former wetlands

12 

APRIL 2008 ARCHAEOLOGICAL SURVEY 

Survey Conditions 

At the time of the survey, land use within the proposed construction corridor included 

mown drainage reserves, pastoral grazing, rank pasture, maize cropping, scrub and 

exotic plantings, disused railway yards, road reserve and small residential sections. 

The current land use within the construction corridor obscured the ground surface or 

prevented access to some areas during the survey. Several areas including railway 

land between Te Maunga and Mangatawa Lane and dunes on the northern side of SH 

2 between Mangatawa Lane and Bruce Road had been extensively modified 

significantly reducing the likelihood of identifying archaeological features. 

Results 

No previously unrecorded archaeological sites with visible surface features were 

identified during the April 2008 archaeological survey of the construction corridor 

between Te Maunga and Domain Road. Subsurface testing and examination of 

existing cuttings and disturbed soils did not reveal evidence for the presence of 

subsurface archaeological features. 

The coordinates provided by the NZAA for the 7 previously recorded archaeological 

sites are accurate to within 10 – 50 metres. All 7 sites are located within private 

properties and at least 100 metres from the construction corridor and as, they are not 

affected by the proposal, were not revisited during the April 2008 survey.

13 

DISCUSSION AND CONCLUSIONS 

Summary of Results 

There are 7 recorded archaeological sites within 300m of the proposed construction 

corridor. None of the 7 sites falls within the affected properties; however, there 

remains a possibility that unrecorded subsurface archaeological sites are present 

within the affected areas which may be disturbed by ground disturbance associated 

with the construction of the Tauranga Eastern Motorway. 

Archaeological Significance 

This part of the Bay of Plenty is rich in archaeological evidence of Maori occupation, 

the majority of recorded archaeological sites relating to the period before the arrival 

of Europeans. The recorded sites may be significant individually because of the 

archaeological information they contain relating to the history of Maori occupation in 

the area, but they also gain significance as components in a wider archaeological 

landscape. The nature and sequence of occupation over time is best understood with 

reference to the full range of sites within the area and the relationship between them. 

Any subsurface archaeological sites that may be present within the construction 

corridor may have the potential to ad to our understanding of the nature and antiquity 

of the surrounding pre European Maori cultural landscape. 

General Considerations 

This is an assessment of archaeological values and does not include an assessment of 

Maori values. Such assessments can only be made by the tangata whenua. 

It should be noted that archaeological survey techniques (based on visual inspection 

and minor sub-surface testing) cannot necessarily identify all sub-surface 

archaeological features, or detect wahi tapu and other sites of traditional significance 

to Maori, especially where these have no physical remains. 

Effects of Proposal 

The proposed construction corridor for the Tauranga Eastern arterial between Te 

Maunga and Domain Road will not impact on previously recorded archaeological 

sites. No previously unrecorded archaeological sites where identified during the April 

2008 archaeological survey. However, in any area where many archaeological sites 

have been recorded in the general vicinity it is possible that unrecorded subsurface 

remains may be exposed during ground disturbance associated with the project. If 

sites are present they would be destroyed by the road construction. Should sites be 

located in the course of road construction, an Authority from the NZHPT would be 

required before work could proceed (see below). It is therefore recommended that an 

Authority is applied for in advance of earthworks as a precaution so that delays can be 

avoided. If sites are present they should be recorded and if necessary investigated 

under the conditions of an Authority from the NZHPT, to mitigate their destruction in 

the course of road construction.

14 

Historic Places Act 

In addition to any requirements under the RMA 1991, the HPA 1993 protects all 

archaeological sites whether recorded or not, and they may not be damaged or 

destroyed unless an Authority to modify an archaeological site has been issued by the 

NZHPT. 

An archaeological site is defined by the HPA 2(a)(i) and 2(b) as: ‘any place in New 

Zealand that was associated with human activity that occurred before 1900, and is or 

may be able through investigation by archaeological methods to provide evidence 

relating to the history of New Zealand’. 

Authorities to modify archaeological sites can be applied for either under Section 11, 

in respect to a particular site or sites, or under Section 12, for all sites that may be 

present within a specified area. Applications made under S12 require approval by the 

Maori Heritage Council of the NZHPT. The tangata whenua should be consulted 

regarding applications to modify or destroy archaeological sites which have Maori 

cultural associations. 

Note that about 4 months should be allowed for the processing of authorities, which 

includes a statutory stand down period of 15 working days before an authority can be 

exercised.

15 

RECOMMENDATIONS 

The following recommendations for avoidance or mitigation are provided as points of 

discussion between the applicant, statutory agencies and tangata whenua. 

1. That consent for the construction of the eastern arterial between Te 

Maunga and Domain Road should not be withheld on archaeological 

grounds as the proposed construction corridor will not have any effects on 

known archaeological sites. 

2. That any potential effects on possible unrecorded sites within the proposed 

construction corridor are mitigated under the provisions of the Historic 

Places Act 1993. Because it is possible that subsurface archaeological 

features may be exposed during the construction, it is recommended that 

an Authority to modify archaeological sites is applied for under Section 12 

of the Historic Places Act and obtained prior to the start of ground 

disturbance. 

3. That all initial ground disturbance and topsoil stripping is monitored by an 

archaeologist to establish whether any subsurface features are present. 

4. That any archaeological sites or features encountered are recorded and/or 

investigated under the conditions of an Authority from the NZHPT. 

5. That in the event of koiwi (human remains) being uncovered, work should 

cease in the immediate vicinity and the tangata whenua, NZHPT and NZ 

Police should be contacted so that appropriate arrangements can be made. 

6. That since archaeological survey cannot always detect sites of traditional 

significance to Maori, such as wahi tapu, the tangata whenua should be 

consulted regarding the possible existence of such sites on the property. 

REFERENCES 

Fredericksen, C., Kahotea, D.T. & M. Felgate. 

1996 An Archaeological Survey of the Papamoa Coastal Zone, Tauranga 

District. Unpublished report prepared for Tauranga District Council 

and New Zealand Historic Places Trust. 

Phillips, K.J.S. 

2004 Preliminary Archaeological Survey: Selected Areas C-K Tauranga 

City. Unpublished report prepared for Tauranga City Council.

APPENDIX 8 - 

Hydraulic Modelling: Mangatawa 

Drain/Maranui Swale – Mitigation 

Options

Report 

Hydraulic Modelling: Mangatawa Drain/Maranui Swale - 

Mitigation Options 

Prepared for New Zealand Transport Agency and Tauranga City Council 

By Beca Infrastructure Ltd (Beca) 

April 2009 

© Beca 2009 (unless Beca has expressly agreed otherwise with the Client in writing). 

This report has been prepared by Beca on the specific instructions of our Client. It is solely 

for our Client’s use for the purpose for which it is intended in accordance with the agreed 

scope of work. Any use or reliance by any person contrary to the above, to which Beca has 

not given its prior written consent, is at that person's own risk.

Hydraulic Modelling: Mangatawa Drain/Maranui Swale - Mitigation Options 

Table of Contents 

1 Project Description.................................................................................................1 

1.1 Introduction.................................................................................................................. 1 

1.2 Background ................................................................................................................. 1 

1.3 Mangatawa Flood Risk and Stormwater Management ............................................... 3 

1.4 Outlet Options Considered .......................................................................................... 3 

1.5 Floodway Concepts..................................................................................................... 5 

2 Model Studies .........................................................................................................6 

2.1 Modelling Stage........................................................................................................... 6 

2.2 Hydrological Assessment ............................................................................................ 8 

2.3 Rainfall......................................................................................................................... 8 

2.4 Hydraulic Model......................................................................................................... 10 

2.5 Results....................................................................................................................... 11 

3 Proposed Flood Risk Mitigation Measures ........................................................15 

3.1 Increased Drain Storage............................................................................................ 15 

3.2 Top Spill Stop Bank................................................................................................... 15 

3.3 Maintenance Work in Mangatawa Drain ................................................................... 16 

3.4 Bruce Road Barrier / Bund ........................................................................................ 16 

3.5 Lower Rail Bridge Embankment Stability .................................................................. 16 

3.6 Flood Bypass from Maranui to Mangatawa............................................................... 16 

3.7 Lower Mangatawa Drain Works ................................................................................ 17 

3.8 Sandhurst Culvert...................................................................................................... 17 

3.9 Extension of Maranui Culvert .................................................................................... 17 

3.10 Maranui Deepening ................................................................................................... 17 

3.11 Stormwater Treatment Wetland Area........................................................................ 17 

4 Conclusions ..........................................................................................................18 

Appendices 

Appendix A – Mangatawa Drain Layout Plan 

Appendix B – Mangatawa Drain Layout Option 2 

Appendix C – Runoff hydrographs 

Appendix D – Longsection of hydraulic grade line 

Appendix E – Proposed Lower Mangatawa Drain and Maranui treatment area 

Beca // 17 March 2009 // Page ii 

3932036 // NZ1-1604459-15 0.15 Rev A

1 Project Description 

1.1 Introduction 

The Mangatawa Drain was constructed many years ago, reportedly when the railway was built 

along the route parallel to what is now SH2. The purpose of the drain was to divert flow that 

previous flowed north into what was at the time farm land but is now Papamoa urban area. 

The Mangatawa Drain is about 2,500m long where it is alongside the proposed Tauranga Eastern 

Motorway (TEM). The drain has a vegetated, earth lined channel that is tightly constrained between 

the railway (to the south) and the highway (to the north). There is some uncertainty as to who owns 

the drain and is responsible for its maintenance, although in the past Tauranga City Council (TCC) 

has undertaken maintenance. It is generally located on either road reserve or railway land. 

In larger flood events excess flow spills north across the highway at two locations, and into the 

Papamoa urban area. The two locations are identified in this report as “Top Spill” and Bruce Road 

(although the spill covers several hundred metres of highway in the general vicinity of Bruce Road). 

While the discharge can be volumetrically large, it is generally spread as a shallow overflow (a few 

hundred millimetres deep) or ponding across several hundred metres length of highway, and has 

resulted in highway closure in the past. The was a closure in May 2005, which lasted for 14 to 18 

hours. The latest event where there was a spill across the highway was on 7 March 2009, but this 

occurred during daylight and the road was not closed. The frequency of spills appears to be about 

5 yearly on average at present. 

TCC has updated their design rainfall figures and these have been applied to this investigation and 

modelling. These design rainfall figures are based on predicted climate changes to 2055. The TCC 

design rainfall figures for 2055 are the basis of the TEM design. These 2055 figures were agreed 

with EBOP and consented. With the climate adjusted rainfall figures the frequency of spills is 

predicted to increase to about 3 yearly without mitigation measures, and to about 10 yearly with 

mitigation in place. 

In addition to closing the highway, the spills discharge into developing urban areas on the northern 

side of the highway, with potential consequences for TCC for flood risk management. 

The Top Spill discharge flows to the Wairakei Stream, where there is significant existing urban 

development, plus plans for growth. This stream has no natural outlet, discharging to ground 

soakage, so is sensitive to additional flood flow volumes. The Bruce Road spill discharges to TCC’s 

Maranui Swale, recently completed and designed to collect and convey urban stormwater along the 

northern side of the highway then under the highway and the railway to the wetland treatment 

ponds, before discharge to the Tauranga Harbour at Rangataua Bay. The swale was originally 

designed without accounting for climate change, or for the effects of the Mangatawa spill, and 

therefore will need significant upgrading to meet design flood level standards in the urban area. 

1.2 Background 

In the 18 May 2005 storm extensive ponding occurred in the Papamoa area. The Mangatawa Drain 

alongside the highway overflowed at two locations. Opus was initially appointed by TCC to 

Beca // 17 March 2009 // Page 1 

3932036 // NZ1-1604459-15 0.15 Rev A

undertake investigations into the drain performance. They produced three reports 1 and the last was 

after the May 2005 floods. As part of their work a MIKE11 hydraulic model was built. 

New Zealand Transport Agency (NZTA) has been working with TCC to find a solution which will 

avoid or at least reduce overflows. The aim for NZTA was to avoid if practicable the 1% Annual 

Exceedance Probability (AEP) storm event overtopping and overflowing the highway, while TCC’s 

aim was to reduce the volume of water that would enter the Papamoa catchment areas (Maranui 

Swale and the Wairakei Stream) such that the design flood level for Papamoa of 4.5m MD (Moturiki 

Datum), as defined in the District Plan, was not exceeded in the 2% annual exceedance probability 

(AEP) storm event. Beca was appointed to adopt the Opus hydraulic model and undertake further 

modelling and engineering work to investigate mitigation options, as an extension to the work they 

were carrying out for NZTA on the TEM. 

Attached in Appendix A is a plan illustrating the various elements within the catchments. 

Regular meetings were held whereby Beca reported to TCC and NZTA on the results from the 

modelling, and options for mitigation works. Various mitigation options were considered and used 

in combinations. These combinations were evaluated based on hydraulic performance and 

financial costs. 

The following are the mitigation options that were considered: 

1. Improve Top Spill only. 

2. Improve Bruce Road Spill only. 

3. Balance spill between Top Spill and Bruce Road – low cost option. 

4. Full mitigation – high cost option. 

The overall hydraulic performance of each option and the cost to construct was assessed and 

Option 3 provided the best benefit relative to cost. Further investigation and modelling indicated 

that the Maranui catchment should be added to the model work, in order to understand the effect of 

water spilling over the highway and what the effect of climate adjusted rainfall figures would be on 

the catchment once fully developed. 

With the inclusion of the Maranui catchment and swale in the model the following objectives were 

identified: 

1. Determine if an increase in capacity of the Maranui swale as a result of the revised TCC design 

rainfall figures is required; 

2. Determine the additional effects of the Mangatawa overflow on the Maranui catchment; 

3. Mitigate the effects to acceptable levels that do not compromise the minimum floor level design 

standard as set by TCC for the Papamoa area; 

4. Determine the culvert sizes required at Sandhurst Road interchange; 

5. Determine the natural available storage within the Bruce Road catchment area; and 

6. Model the effects of a balanced spill approach across the highway at both Top Spill and Bruce 

Road. 

1 Mangatawa Drain Flood Capacity, September 2000; Mangatawa Drain Flood Capacity: Supplementary 

Report, July 2001; and Mangatawa Drain Flood Assessment, 29 November 2006; all produced by 

Opus International Consultants Ltd 


3932036 // NZ1-1604459-15 0.15 Rev A

The Wairakei catchment was not included in the model as it has already been separately and 

comprehensively modelled for TCC by other consultants. This model assumed spills predicted by 

the original Opus modelling. The amount of spill assumed in the Wairakei modelling was lower than 

predicted by recent modelling, but higher than with proposed Mangatawa mitigation in place, as 

shown in the table below. Therefore the Mangatawa mitigation performance will not compromise 

the performance of the Wairakei drainage system. 

Table 1 - 1% AEP spills to Wairakei Catchment 

Wairakei model 

Mangatawa model 

Peak spill rate (m 3 /s) 21.03 17.13 

Spill volume (m 3 ) 151,369 133,103 

1.3 Mangatawa Flood Risk and Stormwater Management 

The previous section outlines the options considered for mitigation, and the history leading to 

selection of options. Later sections of the report describe in some detail the proposed works. This 

section sets out in summary the works proposed for flood risk management of Mangatawa spills 

and for management of stormwater runoff from urban and highway areas, while the next section 

addresses the matter of appropriate outlet for flood flows in particular. 

It is proposed that the urban stormwater runoff from Maranui catchment, the adjacent “Arataki” area, 

from MPBI industrial zoned land south of the State highway, and from the TEM, be captured and 

treated in an expanded wetland treatment area on the site of the current TCC stormwater treatment 

ponds. This would capture flows up to at least the stormwater quality storm, and in some parts up 

to the pipe system capacity of between 20% and 10% AEP. 

To reduce the risk of spill across the TEM and into Papamoa urban area, there are works proposed, 

including some as part of the TEM construction, to increase the capacity of the Mangatawa Drain 

and to contain flood flows within the drain to a higher level than currently occurs before spill. There 

are also works proposed to manage the spills into the Maranui swale area, and to return these 

safely to the harbour (as described in the next section). 

Spill from Mangatawa will still occur in events of about 10% AEP and above, but at a much lower 

volume and flow rate than at present. 

1.4 Outlet Options Considered 

At present the principal Mangatawa/Maranui flood outlets are the Mangatawa Drain itself, and the 

current TCC culvert under SH2 and the railway leading to the stormwater treatment wetland. As 

part of the assessment, four outlet options have been considered and the two most suitable ones 

are illustrated in Appendix B: 

• Pipe the Maranui overflow north to the coast at Papamoa Beach; 

• Pipe the Maranui overflow west past the eastern end of Truman Road and out to the harbour 

through TCC land; 

• Co-locate with the existing outflow from Maranui catchment, with two additional pipes adjacent 

to the current Maranui outlet pipe; 

• Leave the existing Maranui outlet as it is, and provide the overflow capacity through two pipes 

back to the Mangatawa drain immediately west of Mangatawa Lane. 


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Discharge to Papamoa Beach 

To discharge at Papamoa Beach would require a pipeline about 1.8km long. The flood level in the 

Mangatawa Drain upstream of Mangatawa Lane is of the order of 4.2mRL during the 1% AEP flood. 

The existing drain capacity through this area is 17.4m 3 /s, and the additional flow rate that needs to 

be discharged to convey the 1% AEP flood with allowance for climate change is a further 29m 3 /s. 

To convey this quantity by gravity to the coast at Papamoa Beach would require a box culvert with a 

cross-section of approximately 15m 2 (e.g. 10m wide by 1.5 high). This would need an easement of 

at least 17m width, in addition to any existing easements, and would need to be on either the “Rifle 

Range” block or the Asher block, as all other routes are constrained by existing development. The 

outlet to the beach would have significant aesthetic effects, and would affect the morphology of the 

coast, potentially putting the coastal dunes (and hence property behind) at risk. The land required 

would be about 3.06ha, and the construction cost would be prohibitive. Therefore this option is not 

considered practicable. 

Discharge along Truman Lane 

Discharge to the west along Truman Lane then to the harbour would likely require a route that 

followed south of the railway. For this option, some flow would need to be diverted at Mangatawa 

Lane, and conveyed alongside the railway in a box culvert. It would then be joined by additional 

flow from 2 additional pipes from Maranui swale, and piped along the centre of Truman Lane, with 

increased capacity from this point to the harbour. This option would require a 2.6km long box 

culvert of a larger size than the Papamoa Beach option. 

Alternatively, if the box culvert to the harbour only conveyed the estimated additional 8.8m 3 /s 

overflow from Maranui swale, and Mangatawa Drain outlet conveyed the additional flow from 

upstream capacity improvements, then the box culvert could be reduced to 1.8km in length, and 

approximately 4.8 x 1.0m in size. However, with either option there is minimal corridor available in 

places along the route (especially between the TEM, the railway and Truman Lane), and costs 

would again be prohibitive. Therefore this option is not considered practicable. 

Discharge along upgraded existing flow paths 

Of the two remaining options, involving open channel conveyance to the harbour, both follow routes 

already serving as drainage paths, with relatively minor changes in the drainage corridor width 

required. Even if one of the box culvert routes were to be used, the Mangatawa Drain route would 

still need to be able to convey 17.4m 3 /s in the 1% AEP flood, and a stream channel plus flood plain 

would need to be retained. The difference would be the size of flood plain required. Further, both 

of the open channel options involve much less costly construction works, as they make use of 

existing drainage paths, and the principal works required would be earth banks to contain the flow, 

and planting of the flood plains. 

The Maranui corridor south of the railway is about 200m long adjacent to developable land, while 

the Mangatawa corridor is about 800m long adjacent to developable land. Therefore, the total 

footprint of these corridors is 1.7ha for Option 1 and 2.3ha for Option 2. If the Mangatawa Papamoa 

Blocks Inc (MPBI) land were to be developed with the current drainage system in place, and SH2 

and Papamoa were allowed to be flooded, we estimate that these corridors would still require about 

1.5 ha to pass existing flood flows, so the additional land required is only about 0.8ha. 

It should also be noted that the Mangatawa corridor will include flood plain areas that will normally 

be available for public use for passive recreation, so most of that land will have multiple beneficial 

uses. By contrast the Maranui floodway is likely to be permanently wet (as is the present bypass), 

but with no flow, and unlikely to be suitable for multiple uses. It was not intended for recreational 

purposes. Further, we have assumed that the Maranui bypass would be constructed within the land 


3932036 // NZ1-1604459-15 0.15 Rev A

currently leased by TCC for the Maranui pond, and therefore the land available for treatment would 

be reduced if the bypass width increased. From our assessment of TCC, NZTA and MPBI 

development runoff, including the Truman Lane development of MPBI, more land would be required 

to address stormwater quality treatment and mitigation and the area located to the south east of the 

current pond outlet is ideally suited as it is not constrained by any proposed land use or known 

special ecological area. 

Redirecting the flood overflow back to the Mangatawa Drain at Mangatawa Lane also reduces the 

flood flow that needs to be taken past the Sandhurst interchange and into the Asher block, thereby 

reducing the effect on the western end of the Maranui swale. 

The outlet flow path from the Maranui stormwater treatment pond flows for 400m through the 

Special Ecological Site 13 (as shown in the District Plan) before reaching the harbour, with the risk 

of occasional damage to this area during floods if a Maranui flood outlet is used. The Mangatawa 

flood bypass discharge is directly along the Mangatawa Drain to the harbour, with only a minor 

impingement on one end of SES 13, reducing this risk. 

Therefore, the better overall outcome for the MPBI development and the environment is likely to be 

to minimise the width of the Maranui flood bypass and increase the Mangatawa flood plain width to 

compensate, as the flood plain can be integrated with the possible future MPBI development. 

The proposed design involves no change to the size of the Mangatawa main channel. The 

increased flood flows would be conveyed principally in the flood plain, with the normal (dry-weather) 

flow contained in the main channel, and therefore the shear stress on the channel bed will not 

increase by more than a minor amount. This serves to protect the channel from erosion, and helps 

to preserve its character. This is the same process as occurs in natural river systems, where the 

main channel usually only conveys small floods, and larger floods spill onto the flood plain. 

In comparing the two principal options, the Mangatawa flood bypass option appears to have more 

merit overall. The positives are: 

• The required flood corridor is more usable in this location. 

• Provides greater protection and less through flow in the western end of the Maranui swale. 

• Leaves more space for the Maranui treatment wetland. 

• Has less effect on Special Ecological Site 13. 

• Lower cost overall. 

• Can be integrated with the MPBI development and aesthetics and use of the area. 

• Appears to fit within the riparian area shown on the MPBI development concept, so there would 

be no change to the usable area of the development. 

The aspects where the Mangatawa flood overflow has less merit are: 

• A slightly larger area is needed for floodway corridor. 

As a consequence, this report has focussed on the flood bypass and outlet option that returns 

excess flow to the Mangatawa Drain at Mangatawa Lane, and does not change the current Maranui 

outlet under SH2 at the Asher Block. However, for comparison purposes, the report presents 

results for that alternate option as well. 

1.5 Floodway Concepts 

We have considered the form that the Mangatawa Drain should take, considering the multiple 

purposes which the corridor would need to serve. The identified objectives and actions are: 

• Stable drain banks, reduced risk of erosion; 


3932036 // NZ1-1604459-15 0.15 Rev A

• Riparian planting adjacent to the channel for cover and bank protection; 

• Access for whitebaiting and other stream-related activities; 

• Provide floodway capacity, while retaining multi-use capability for most of the time when there 

is no flooding (e.g. grassed area for picnicking, specimen trees, etc); 

• Reliable access along one bank for long term maintenance. 

The alternative flood bypass outlet from the Maranui swale to Mangatawa Drain near Mangatawa 

Lane, upstream of the proposed Sandhurst Drive, is proposed in this report. 

The following engineering solutions were included: 

1. Install 2 x 2.1m diameter pipe culverts below the TEM and the railway track. The inlet to be 

from the Maranui Swale, with a weir to control the inlet to allow the “first flush” to continue along 

its current path, and the outlet immediately upstream of the Mangatawa Drain vehicle bridge on 

Mangatawa Lane; 

2. Provide one 1.8m diameter pipe culvert under Sandhurst Interchange for day-to-day drainage 

and for the “first flush” water to be conveyed for treatment at the stormwater treatment wetland; 

3. Utilise the existing 1.8m diameter pipe culvert that discharges from the Maranui Swale to the 

stormwater treatment wetland to pass this flow south for treatment; 

4. Enlarge the wetlands to treat the additional urban and highway area that will reach it (including 

the development of the MPBI land);and 

5. Formalise and protect the flood plain alongside the Mangatawa Drain from Mangatawa Lane to 

the harbour. 

2 Model Studies 

Opus was initially appointed by TCC to under take investigations into the drain performance, with a 

specific focus on predicting the frequency and rate of overflow. They produced three reports 2 and 

the last was after the May 2005 floods. They carried out their analysis using a model developed in 

MIKE11 software. 

Beca adapted the Opus model and during the ongoing modelling process three stages were 

undertaken where the model was adapted to asses specific options and outcomes. Two of these 

stages included the inclusion of the Maranui Swale and MPBI area, and the assessment of a range 

of mitigation options. 

2.1 Modelling Stage 

2.1.1 Preliminary 

The Opus model was used as a basis for current work, but has been extensively updated to reflect 

the needs of ongoing analysis. The following lists the amendments to the model: 

• Included two additional catchment areas (P2 and P3) 

• Included natural occurring storage areas 

• Added some secondary drains 

2 Mangatawa Drain Flood Capacity, September 2000; Mangatawa Drain Flood Capacity: Supplementary 

Report, July 2001; and Mangatawa Drain Flood Assessment, 29 November 2006; all produced by Opus 

International Consultants Ltd 


3932036 // NZ1-1604459-15 0.15 Rev A

• Added primary drain cross-sections to reflect updated topographic data 

• Adjusted Kairua road culverts to reflect existing situation 

• Included the Maranui catchment of which the details are: 

- Catchment and natural storage areas 

- Swales 

- Culverts 

- Outlet to harbour 

2.1.2 Mitigation 

Using the above update, various mitigation options were investigated and the options that provided 

satisfactory results and were cost effective are: 

• Additional storage within the drains. 

• Stop banks along the drain located at the two known spill points. 

• Drain improvements, clearing of vegetation and replant with vegetated lining. 

• Protection and stabilisation of drain bank in specific locations. 

• Decrease secondary losses through the railway bridge crossing. 

• An alternative outlet from the Maranui swale to the Mangatawa Drain was included through the 

inclusion of the following details: 

- 

- 

Additional culverts below the highway and the railway track. 

A weir to allow flood spill but contain and bypass the first flush water to the Maranui swale 

and pond. 

2.1.3 Inclusion of MPBI land 

Further refinement in the model was later carried out to address the effects on the MPBI industrial 

land south of the State highway. The aim of the refinement was to optimise the available MPBI 

land. This refinement in the model included the following amendments: 

• Replace the open drain with an extension of the current 1.8m diameter Maranui Swale outlet 

pipe culvert from its current outlet up to the treatment pond. 

• Optimise both the Maranui swale and Mangatawa drain floodway corridor options. 

• Improve the current pond to a stormwater wetland area that provides treatment for MPBI, TCC 

and NZTA. 

2.1.4 Summary 

The following is a summary of the mitigation work that is included in the modelling and is illustrated 

in the drawings in Appendix A: 

• Provide stopbank and flood retention “bund”. 

• Enlarge the flood storage area within the drain. 

• Drain improvements, clearing of vegetation and replant with vegetated lining. 

• Protection and stabilisation of drain bank in specific locations. 

• Decrease secondary losses through the railway bridge crossing. 

• Deepening of Maranui swale. 

• Additional culverts to drain from the Maranui swale to the Mangatawa Drain. 

• Improve the lower Mangatawa drain conveyance capacity. 

• Extend the existing Maranui outlet culvert. 

• Extend the Maranui stormwater treatment pond as a wetland. 


3932036 // NZ1-1604459-15 0.15 Rev A

2.2 Hydrological Assessment 

2.2.1 Catchments 

The Papamoa Hills area is the major catchment contributing to the Mangatawa Drain runoff; see 

Appendix A for the illustration of the catchment boundaries. The southern rural catchments flow 

directly into the drain and thence without treatment into the harbour, at Rangataua Bay. The 

northern (urban) catchment drains into the Maranui swale and is treated in the Maranui Pond before 

also discharging to Rangataua Bay. The current SH2 runoff is partly to the Mangatawa drain, and 

partly to the Maranui swale. For the proposed TEM this will change, with both the southern and 

northern carriageway draining into the Maranui swale and being treated in the Maranui Pond. 

The following table summarise the catchments and the pervious and impervious areas. 

Table 2 - Catchment Areas (km 2 ) 

Catchment 

Residential lots 

Pervious Imperv. 

Roof 

Roads 

Pervious Imperv. 

Rural 

Total 

P1 – central Lots 10.75 10.75 

P2 – east 2.69 2.69 

P3 – west 3.03 3.03 

Maranui 0.685 0.279 1.167 0.102 0.305 0.606 3.14 

SH2/ TEM 0.030 0.148 0.18 

Total 0.685 0.279 1.167 0.132 0.453 17.076 19.79 

This does not include the MPBI land to the south west, which does not directly affect the principal 

flood management works addressed in this report. 

2.3 Rainfall 

The TCC design rainfall estimates based on 2055 projected climate change 3 were used. Temporal 

patterns from that report were used to develop hydrographs that were included in the hydraulic 

model software. The 6 hour storm was used by Beca as it was identified in the initial work as 

producing the highest flow rate for the central catchment (P1) of Papamoa Hills. For the Maranui 

catchment the 5 hour storm produced the critical storm. The following table summarises the input 

data used in the model work for the catchments. 

3 Tauranga City High Intensity Rainfall Update, October 2005, and Tauranga City Temporal Rainfall using the 

Average Variability Method, May 2006, both produced by Opus International Consultants Ltd 


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Table 3 – Catchment rainfall depth (mm) 

Storm events (% AEP) Maranui Mangatawa 

10 121 131 

5 147 159 

2 183 197 

1 209 225 

The SCS 4 method was used as the basis for deriving a runoff coefficient. The following is the runoff 

curves (CN values) adapted for the various surface areas. 

Land use and type 

CN value 

Lots and roads pervious 22 

Lots and roads impervious 95 

Roof impervious 98 

Roads impervious 95 

For the Maranui residential area an overall CN value (run-off coefficient) of 59% was applied. 

For the other catchments (P1 to P3) refer to the Opus reports for the background information. 

2.3.1 Runoff Model 

The initial model work covered the hydrology analysis and the calibration of the model and was 

reported as an update of the system performance work 1 . The number of catchments in the model 

was increased by Beca to be representative of the pre and post development scenarios. 

The following tables summarises the volume of runoff for the catchments: 

Table 4 - Catchment runoff volumes (m 3 ) 

Storm event 

(%AEP) 

P1 P2 P3 Maranui 

10 449,102 148,381 161,550 136,631 

2 861,951 285,378 306,791 271,319 

1 1,071,899 352,035 378,317 333,370 

4 US Department of Agriculture, Soil Conservation Service 


3932036 // NZ1-1604459-15 0.15 Rev A

The Maranui catchment area in the model is 2.77 km 2 and includes the TEM catchment area and 

excludes the Arataki residential area and a small portion of rural land north of Kairua Road. The 

reason for including TEM catchment area was that the proposed mitigation measure will divert 

water to the Maranui swale. The following is a summary of the catchment information: 

Table 5 - Catchment peak flow rates (m 3 /s) 

Catchment 10% AEP 2% AEP 1% AEP 

P1 – central 28.67 54.74 66.50 

P2 – east 14.92 25.62 31.64 

P3 – west 6.79 10.76 15.39 

Maranui 11.50 22.66 27.69 

TEM 

- A 

A – TEM has an extended catchment that essentially contributes to two catchments and therefore does not have a distinct primary flow hydrograph. 

See Appendix C for the runoff hydrographs for the following catchments P1, P2 and P3. 

2.4 Hydraulic Model 

2.4.1 Sources of Information 

The following information was sourced to assist in producing a hydraulic model that is 

representative of the catchments and meets the mitigation objectives of the project: 

• MIKE11 hydraulic model, Opus International Ltd 

• Additional cross-section information of Mangatawa drain, Opus International Ltd 

• LiDAR data of the areas surrounding the drains, TCC 

• Papamoa East as-built information of roads and stormwater data, TCC 

• Maranui swale, culvert and treatment pond design information, Shrimpton and Lipinski Ltd 

• Maranui swale, as-built information, TCC 

• MPBI conceptual development plans, Harrison Grierson Consultants Ltd 

• Isthmus proposed Maranui treatment pond and Mangatawa Drain 

2.4.2 Mitigation Objectives 

The primary aim of the parties was to reduce the number of highway closures and the volume of 

water spilling into the Maranui and Wairakei catchments without negatively affecting the 

surrounding environment. The parties aim to achieve this through the provision of engineering 

solutions, e.g. additional storage and conveyance in the Mangatawa Drain, Maranui swale system. 

A comprehensive list of work is provided in Section 2.1. 

2.4.3 Parameters Assessed 

The model was used to assess the following parameters: 

• Flooding across the highway 

• Maximum flood water levels in the catchments for the 1% AEP event 

• Residence time of water in each catchment for the 1% AEP event 

• Water levels, peak flow rates and velocities along the following two drainage paths: 

Upper and lower Mangatawa Drain defined by the rail bridge 

- 

- 

Maranui pond floodway corridor 


3932036 // NZ1-1604459-15 0.15 Rev A

It should be noted that while the TCC District Plan specifies a 2% AEP flood level for Papamoa of 

4.5m RL recent work in the Wairakei catchment has focussed also on the 1% AEP events with 

maximum flood level of 4.6m RL. Both have been considered in the performance target for this 

work. 

2.5 Results 

The mitigation and engineering measures listed in Section 2.1 and performance results are reported 

in this section. The table below summarises the 10%, 2% and 1% AEP storm event results. The 

long section taken on the centreline of the highway is included in Appendix D. Illustrated on the 

long section are the 1% AEP hydraulic grade line and the stop bank levels at Top spill and Bruce 

spill. The results reported in the following two Tables below shows that the spill rate across the 

highway at Bruce Road will increase with mitigation but the flood depth will decrease. The reason 

for this result is that more water is diverted downstream with the mitigation measures and the spill at 

Bruce will occur over a longer section of the highway. 

Table 6 – 10% AEP Storm Event 

Top Spill 

Bruce Road 

Existing Future Existing Future 

Flood depths over TEM (mm) 280 0 290 0 

Spill rate (m 3 /s) 16.68 0 2.86 0 

Spill volume (m 3 ) 144,154 0 35,576 0 

P1 - Central P2 – East P3 – West 

Existing Future Existing Future Existing Future 

Flood levels 

(mRL) 

8.19 8.07 8.23 8.22 4.96 4.91 

Flood 

residence 

time (hours) 

12.0 8.5 9.0 8.7 10.4 4.9 

The flood residence time is based on time above the following levels. These levels were taken in each catchment as follows: P1: 7.15mRL; P2: 7.5mRL 

and P3: 4.6mRL and represent time that ponding occurs out of channel, upstream (south) of the railway 


3932036 // NZ1-1604459-15 0.15 Rev A


Top Spill 

Bruce Road 


Flood depths over TEM (mm) 330 70 290 110 

Spill rate (m 3 /s) 37.7 8.13 6.06 13.06 

Spill volume (m 3 ) 469,026 44,823 94,460 144,826 

Flood levels 

(mRL) 

Flood 

residence 

time (hours) 



8.80 8.70 8.86 8.87 5.61 5.60 

17.5 11.4 15.2 13.1 14.1 8.0 

The flood residence time is based on time above the following levels. These levels were taken in each catchment as follows: P1: 7.15mRL; P2: 7.5mRL 

and P3: 4.6mRL and represent time that ponding occurs out of channel, upstream (south) of the railway 


Top Spill 

Bruce Road 


Flood depths (mm) 360 140 290 120 

Spill rate (m 3 /s) 47.25 17.13 9.17 15.29 

Spill volume (m 3 ) 638,424 133,103 133,509 204,236 

Flood levels 

(mRL) 

Flood 

residence 

time (hours) 



9.11 9.0 9.15 9.06 5.80 5.79 

19.15 12.6 17.94 14.5 15.37 8.9 

A property located in the lowest part of catchment P1 has a building floor level at 9.65m RL, and 

thus will not be affected. There are no known buildings located in the lower-lying part of catchment 

P2 and P3. 

In order to report duration of flooding in each catchment, levels were selected close to the top of the 

existing drains. This is to report when water is outside the farm drain and thus flooding occurs. 

This level was also selected based on available data from the model where a full reporting period 

(start and end time) was available. 

The spill rate at Bruce Road will increase with the mitigation measures for the future option. This 

increase will be accommodated with the provision of additional storage capacity within the Maranui 

Swale and providing two additional pipe culverts that will offset the effects and thus convey the 


3932036 // NZ1-1604459-15 0.15 Rev A

increase in spill rate from the Maranui Swale to the Mangatawa Drain. The additional 2 x 2.1m 

diameter pipes culverts will covey 16.4m 3 /s for the 1% AEP storm event. 

The following table summarises the 1% AEP results along the Maranui floodway and lower 

Mangatawa drain. The results were taken downstream of the highway and the lower rail track for 

the Maranui and Mangatawa drain respectively. 

The current day to day flows along the Mangatawa Drain will remain the same. The peak rate 

however can be higher than the present due to the drain improvements, for storms greater than 

about the 20% AEP storm. 

Table 9 – Hydraulic Results 10%AEP 

Flood 

Bypass 

Outlet 

Option 

Corridor 

width 

(m) 


Peak 

flow rate 

(m 3 /s) 

Peak 

water 

level (m) 

Peak 

velocity 

(m/s) 

Corridor 

width 

(m) 

Maranui Floodway 

Peak 

flow rate 

(m 3 /s) 

Peak 


level (m) 

Peak 

velocity 

(m/s) 

Unmitigated 5 10.39 1.73 0.99 24 7.78 1.60 1.44 

Mitigated 25 A 30.8 2.74 1.30 12 B 6.18 1.64 1.30 

A - At drain chainage 3,287m 

B – At drain chainage 2,820m. Thus 24m from the extended culvert outlet in the wetland treatment area 


Flood 

Bypass 

Outlet 

Option 

Corridor 

width 

(m) 


Peak 

flow rate 

(m 3 /s) 

Peak 


level (m) 

Peak 

velocity 

(m/s) 

Corridor 

width 

(m) 


Peak 

flow rate 

(m 3 /s) 

Peak 


level (m) 

Peak 

velocity 

(m/s) 

Unmitigated 5 15.35 1.80 1.02 24 7.66 1.83 1.44 

Mitigated 25 A 42.16 2.95 1.50 12 B 6.43 1.64 1.34 


Flood 

Bypass 

Outlet 

Option 

Corridor 

width 

(m) 


Peak 

flow rate 

(m 3 /s) 

Peak 


level (m) 

Peak 

velocity 

(m/s) 

Corridor 

width 

(m) 


Peak 

flow rate 

(m 3 /s) 

Peak 


level (m) 

Peak 

velocity 

(m/s) 

Unmitigated 5 17.39 1.82 0.99 24 9.10 1.88 1.45 

Mitigated 25 A 46.92 3.03 1.5 12 B 6.51 1.64 1.35 

In terms of risk, peak flow and volume of spill, a range of return periods were analysed early in the 

modelling process. The results, presented on the basis of return period, are set out below. There 

are slight differences in volume between these results and those in the previous tables, reflecting 

minor changes that have occurred as the design concepts and models have evolved. The full range 

of return periods has not been remodelled in the more recent work, but the results are still useful in 

understanding the benefits of the works. 


3932036 // NZ1-1604459-15 0.15 Rev A

These results include climate change, and therefore the “existing situation” presented reflects a 

lower performance than would occur under current climate conditions. 

The implication of Graph 1 is that the return period for a spill will improve from 33% to 13% AEP 

storm events. 

Graph 1 - Top Spill and Bruce Road peak discharges 

Top Spill and Bruce Rd - Peak Spill Discharge 

[Unmitigated and Mitigated] 

90.0 

80.0 

83.5 

Peak flow (m³/s) 

70.0 

60.0 

50.0 

40.0 

30.0 

20.0 

19.5 

43.8 

21.2 

56.4 

32.4 

41.6 

10.0 

100% 

0.0 

0.0 

10% 

1% 

Annual Exceedence Probability (AEP) 

Mitigated Unmitigated Log. (Unmitigated) Log. (Mitigated) 

0% 

The volume of discharge across the highway is illustrated in the following graph for the mitigation 

option. 

Graph 2 - Top Spill and Bruce Road discharge volume 

Top Spill and Bruce Road - Spill Volume 

1,600,000 

[Unmitigated and Mitigated] 

1,400,000 

1,381,735 

Volume (m³) 

1,200,000 

1,000,000 

800,000 

600,000 

563,486 

771,933 

743,459 

400,000 

200,000 

179,730 

189,649 

337,339 

0 

100% 

0 

10% 

1% 

Annual Exceedence Probability (AEP) 

Mitigated Unmitigated Log. (Unmitigated) Log. (Mitigated) 

0% 


3932036 // NZ1-1604459-15 0.15 Rev A

The total volume of water spilling across the highway will decrease with the proposed works. The 

implication of Graph 2 is that spill occurrence will improve from 15% to 7.5% AEP events. The 

difference in prediction of return period between the peak flow and the volume graphs reflects nonlinearity 

of the system response, and the difficulties of fitting a suitable curve to the resulting output 

data. The precise return periods are of less relevance than the significant reduction in peak flow 

and volume that the graphs illustrate. 

3 Proposed Flood Risk Mitigation Measures 

To be able to mitigate and manage the spills and flood risk, the current structures and natural drains 

have to be upgraded. This will involve new structures to be constructed and existing ones 

upgraded or expanded. The following are the various mitigation measures that would be required to 

enable the mitigation and management of flood risk, as set out in the modelling. 

3.1 Increased Drain Storage 

On the eastern side of Kairua Road, enclosed between the rail track and the highway, we have 

identified a potential storage area that can be used to create more flood storage in the Mangatawa 

Drain. The land is owned by Ontrack and is not currently in use. Our understanding is that this area 

was used in the past as a station for the moving of cattle. Ontrack does not plan to make use of this 

area. They require a 14m wide strip along the track to ensure that the track can be doubled either 

side in future. 

We are proposing to excavate 25,000m 3 and this will involve excavating a set distance from the 

current and possible future additional track at a 1 in 5 batter to a level set above the current drain 

invert. The current drain will serve as the main channel with the new floodplain set slightly higher. 

Attached in Appendix E are the engineering drawings that illustrate the layout and cross-sections 

along the drain. We do not envisage moving the current drain alignment. The creation of this 

additional storage will require excavation in the drain, conveying of the excavated material and the 

planting of the newly shaped drain and flood plain. 

3.2 Top Spill Stop Bank 

Currently there is an earth bund that starts from the rail track where the central (P1) and western 

(P2) catchments of Papamoa hills drain under the rail track. At present it is not clear who is 

responsible for maintenance of this bund. Local residents report that it has failed several times in 

the past, apparently due to substandard works having been undertaken, or adjacent works that 

compromise its integrity. 

We propose to also use an earth bund that will follow the drain alignment on the northern side 

between the drain and the TEM, constructed to adequate engineering standards to contain the flow 

within the drain, and with a protected face on the TEM side to cope with spills in more extreme 

floods. The bund will be set higher (8.1m) and will be 3 metres wide at the top with 1 in 3 batters. 

The batters will tie into the existing ground profile. The total estimated fill volume will be 3,500m 3 . 

The bund will run from the rail track up to a high point along the proposed TEM where a crash 

barrier will continue along to Kairua Road. The bund will be designed to operate in the same 

manner as the current where it can be overtopped and thus will require reinforcement and 

maintenance. The earth bund will be easier to maintain with a 3 metre wide top and appropriately 

vegetated batters. The creation of the earth bund will require importing material and working 

alongside the current drain. 


3932036 // NZ1-1604459-15 0.15 Rev A

3.3 Maintenance Work in Mangatawa Drain 

The current drain is over grown with shrubs and long grass and weeds. We propose to remove the 

current plant growth and replant the drain with a grass and appropriate low-growing frangible native 

plants that will improve the hydraulic conveyance. The invert of the drain is undulating in places 

and we also propose to grade the invert of the drain to a more uniform grade. 

We note that currently the drain contains parrots feather and reed sweet grass which are invasive 

weeds that block waterways. An active programme will be needed in conjunction with TCC and 

EBOP to remove this weed. 

3.4 Bruce Road Barrier / Bund 

Currently there is no water barrier along this section to prevent over flows. We propose to install a 

concrete barrier structure that will follow the road alignment between the drain and the TEM, 

constructed to adequate engineering standards to contain the flow within the drain. The structure 

will be set to contain and allow spill across the TEM at a controlled section. The height of the 

barrier varies and follows the grade of the road. On average the barrier is 0.45m high above finish 

road centreline level. 

3.5 Lower Rail Bridge Embankment Stability 

The current drain alignment at the lower rail bridge has to flow through two 90 degree bends when 

passing under the rail bridge upstream of Mangatawa Lane. Erosion of the embankments is evident 

especially on the upstream side of the rail bridge. The fluctuation of the water levels in the drain 

and fast flowing water can potentially worsen erosion and the fact that there is no well established 

natural ground cover along the sides exacerbates the risk. The modelling work we have undertaken 

has indicated this section of the drain to be a pinch point resulting in more than expected hydraulic 

losses through this section of the drain and thus causing water to back-up, increasing the water 

level and spills upstream near Bruce Road. 

The work we are proposing to reduce the hydraulic losses through this section is to limit changes in 

the drain cross-section profile and improve the alignment by having smoother transitions before and 

after the bridge. The work is to tie into the rail bridge abutments as we do not want to alter the 

existing structure. We have selected the following drain profile: 

• Bottom width, 8 metre wide. 

• Side batters, 2V in 1H. 

• Top width, 12 metre wide. 

We have selected as part of the cost benefit exercise, “Gabion” walls and “Reno” mattresses to 

create a stable cross-section profile that would be able to convey flood flow and improve 

embankment stability. We have identified the start of the realignment of the drain 120 m upstream 

of the rail bridge with a 90 degree long radius curve directly up and downstream of the bridge. The 

long radius bends have radii of 25 metres and the final transition back to the natural drain is 70 m 

below the bridge. 

3.6 Flood Bypass from Maranui to Mangatawa 

As discussed in Section 1.4 of this report we propose to install two 2.1 diameter pipe culverts under 

the highway and railway track that would link the Maranui to the Mangatawa drain. The Maranui will 

potentially spill 6 times a year over the weir. The location of the discharge point in the Mangatawa 

Drain will be just upstream of the Mangatawa Lane Bridge. This bypass would provide an additional 

flood outlet for the Maranui Catchment and a weir will control the flow in such a way as to direct all 


3932036 // NZ1-1604459-15 0.15 Rev A

water up to a third of a 50% AEP (water quality event) storm event to the existing outlet for 

treatment. Any storm event bigger will be able to spill over the weir and thus provide additional 

capacity during flood events for water to drain away. 

3.7 Lower Mangatawa Drain Works 

In line with MPBI development, we propose to create a 25m wide flood corridor that is 800m long 

and will start downstream of the Mangatawa Lane Bridge and extend to the Special Ecological Site. 

We propose to improve the drain and create flood plains on either side of the drain to contain flood 

flows and reduce the potential for scouring of the drain during flood events. 

The top of the western bank will tie in with MPBI development and provide flood protection. 

The drain improvements include the following: 

• Native grasses along the drain edge. 

• Native trees along the drain on both sides outside the 100% ARI storm event flood level. 

• Flood plains and batters covered in grass. 

• Access for maintenance. 

• Walking track. 

3.8 Sandhurst Culvert 

A 1.8 metre diameter culvert under the proposed Sandhurst interchange has been allowed for and 

this is to convey Maranui swale flows past the interchange. The culvert is estimated to be 100m 

long with concrete inlet and outlet structures. 

3.9 Extension of Maranui Culvert 

The current Maranui swale outlet to the treatment pond is through a 1.8m diameter culvert, that is 

300m long and drains from the Maranui swale under SH2 and the rail track. The culvert discharges 

80m upstream of the treatment pond in an open drain. To remove the open drain and release the 

land for development, we have identified the potential for changing the current open drain to a 

culvert. The culvert will be extended at the same size through to the stormwater wetland area, and 

will have a new concrete outlet structure. The proposed extension is 80m long. 

3.10 Maranui Deepening 

Deepening the Maranui swale will create additional storage capacity within the swale. This will 

provide for the increased runoff from the future development and the impact of the climate adjusted 

rainfall. This storage will be required in future when the Maranui catchment is fully developed and 

for the potential impact of the increase of bigger rain events. The current swale has generally a 

1V:5H side batter and we have allowed for side batters of 1V:4H plus deepening of the swale invert 

by 0.75m. 

3.11 Stormwater Treatment Wetland Area 

The current Maranui stormwater pond has been built and managed by TCC on land that is leased 

from MPBI, and is for the treatment of the residential areas within the Maranui catchment. There 

are two culverts that drain to the open drain upstream of the treatment pond. The one culvert is a 

1.2 metre diameter culvert from the Arataki residential area and the other is the 1.8 diameter culvert 

from the Maranui swale. TCC holds a consent (Consent No. 60061) to discharge treated 


3932036 // NZ1-1604459-15 0.15 Rev A

stormwater from the Maranui catchment to the harbour at Rangataua Bay. TCC has expended 

considerable effort to improve the natural character of the wetland area and mature trees can be 

found here. TCC, NZTA and MPBI have agreed to work together and expand the current treatment 

area to serve the stormwater needs of all parties. A stormwater wetland was identified as the 

appropriate mitigation device to provide treatment for stormwater. 

The following principles have been agreed: 

• Utilise the current lease area. 

• Retain as much of the higher value established trees and plants as practicable. 

• Not to encroach on the Special Ecological Site 13 located on the south of the treatment area. 

• Able to receive and treat stormwater from TCC’s residential areas, MPBI proposed industrial 

land and the TEM. 

• Not to encroach on the existing and proposed pipeline easements that TCC has to the west, 

along the property boundary. 

• Apply ARC TP10 design standards for the upgrading of the wetland. 

The following table is the stormwater runoff for the water quality storm events. 

Party 

TCC (Maranui 

and Arataki) 

Table 12 – Stormwater Treatment Requirement 

Pervious area 

(km 2 ) 

Impervious area 

(km 2 ) 

Catchment area 

(km 2 ) 

Volume required 

(m 3 ) 

0.79 1.75* 2.54 12,941 

MPBI (Industrial) 0.01 0.45 0.46 11,635 

TEM (Motorway) 0.04 0.15 0.19 3,247 

Total 0.84 2.35 3.19 27,823 

* Note this includes roof area, which is disposed to ground and does not contribute to total water quality 

volume 

For the wetland upgrading the 2055 design rainfall required an area that could not be 

accommodated within the area currently available. For the wetland upgrading the 2005 design 

rainfall figures was used instead and a third of a 50% AEP 24 hour design storm event to determine 

the runoff. All residential roof runoff for the TCC areas was assumed to go to ground (soakage). 

This is in line with TCC design approach for the residential areas in the Maranui and Arataki areas. 

There is a potential 4.47ha area available east of the current wetland area, enclosed between MPBI 

proposed development, the existing wetland, and Special Ecological Site 13. We have included in 

our work the additional potential treatment area and attached in Appendix E are the layout and 

cross-section drawings for the extended treatment area. 

4 Conclusions 

There is currently an unacceptable risk of flooding across SH2 into the Papamoa urban area. Both 

TCC and NZTA are seeking to reduce that risk, so that: 

• The frequency and consequences of highway closures are reduced to acceptable levels; 


3932036 // NZ1-1604459-15 0.15 Rev A

• The spills into Papamoa urban area to not result in flood levels that exceed those implicit in the 

District Plan in the context of minimum building platform levels. 

Modelling has been undertaken to determine the current risk, and evaluate options to reduce that 

risk. Recommended works include: 

• Increasing the capacity of the Mangatawa Drain and to contain flood flows within the drain to a 

higher level than currently occurs before spill; 

• Improving the capacity of the Maranui swale to contain spills that do occur; 

• Providing a flood overflow from the Maranui swale back to Mangatawa Drain at Mangatawa 

Lane, associated with bank protection works along the lower Mangatawa Drain; 

• Increasing the capacity of the current TCC stormwater treatment wetland to also treat the runoff 

from the TEM and from proposed development of MPBI industrial zoned land south of the 

railway. 

The modelling confirms that appropriate outcomes can be achieved with the works proposed. 


3932036 // NZ1-1604459-15 0.15 Rev A

Appendix A 

Mangatawa Drain Layout 

Plan

Appendix B 

Mangatawa Drain Layout 

Option 2

Appendix C 

Runoff Hydrographs

Appendix D 

Longsection of Hydraulic 

Grade Line

Appendix E 

Proposed Lower Mangatawa 

Drain and Maranui Treatment 

Area

APPENDIX 9 - 

Drawings 3932036 ck143 Rev C, 

3932036 ck144 Rev E, 3932036 ck 

145 Rev E, 3932036 ck 146 Rev E, 

3932036 ck473 Rev A

APPENDIX 10 - 

Drawings 3932036 ck460 Rev A, 

3932036 ck461 Rev A, 3932036 ck 

462 Rev A, 3932036 ck467 Rev A, 

3932036 ck 468 Rev A, 3932036 ck 

469 Rev A

APPENDIX 11 - 

Drawing 3932036 ck431 Rev B

APPENDIX 12 - 

Drawing 3932036 ck227 Rev D

APPENDIX 13 - 

Example Erosion and Sediment 

Control Plan

Report 

Tauranga Eastern Motorway - Mangatawa Section - 

Erosion and Sediment Control Plan 

Prepared for NZ Transport Agency (NZTA) (Client) 

By Beca Infrastructure Ltd (Beca) 

1 April 2009 

© Beca 2009 (unless Beca has expressly agreed otherwise with the Client in writing). 

This report has been prepared by Beca on the specific instructions of our Client. It is solely 

for our Client’s use for the purpose for which it is intended in accordance with the agreed 

scope of work. Any use or reliance by any person contrary to the above, to which Beca has 

not given its prior written consent, is at that person's own risk.

Table of Contents 

1 Introduction.............................................................................................................1 

2 Site Description ......................................................................................................1 

2.1 Geology ....................................................................................................................... 1 

2.2 Ecology........................................................................................................................ 2 

3 Construction Details ..............................................................................................2 

3.1 Construction Methodology........................................................................................... 2 

3.2 Construction Sequence ............................................................................................... 5 

3.3 Permanent Stormwater Management ......................................................................... 5 

4 Erosion and Sediment Control..............................................................................5 

4.1 Principles of Erosion and Sediment Control................................................................ 5 

4.2 Erosion and Sediment Control Measures.................................................................... 6 

4.3 Erosion and Sediment Control implementation Sequence........................................ 10 

5 Monitoring and Maintenance...............................................................................11 

Appendices 

Appendix A - Erosion and Sediment Control Plan Drawings 

Beca // 1 April 2009 // Page ii 

3932036 // NZ1-1453076-10 0.10

1 Introduction 

This report describes the key principles of erosion and sediment control to be employed for land 

disturbing activities to be undertaken in association with the construction of the Tauranga Eastern 

Motorway (TEM). The NZ Transport Agency (NZTA) will engage a Design and Build Contractor to 

deliver this project. This Contractor will be responsible for preparing the detailed erosion and 

sediment control plans (ESCP) based around their construction methodology. The erosion and 

sediment control measures are to be designed and implemented in accordance with Environment 

Bay of Plenty Guideline No. 2001/03 “Erosion and Sediment Control Guidelines for Land Disturbing 

Activities, September 2001”. 

The resource consent applications lodged with Environment Bay of Plenty (EBOP) in 2008 for the 

majority of the TEM project (excluding the Mangatawa Drain works) contained an example ESCP. 

Under those consents the Contractor will be required to submit an overall ESCP with EBOP at the 

time of construction which will be a contractual requirement between NZTA and the Contractor. 

A separate resource consent is now being applied for the works associated with the Mangatawa 

Drain. This ESCP provides information to demonstrate that appropriate erosion and sediment 

control measures can be implemented by providing a plan for the Mangatawa Drain, the stormwater 

wetland area, a typical culvert installation, and rail bridge embankment stability works. These areas 

are representative of much of the project’s construction activities and working area. It is noted that 

the application for the earthworks associated with the main line TEM project was included in the 

2008 application. 

The ESCPs described in this report are shown on Drawing No.s 3932036-C142, 3932036-CK473, 

32932036-CK467A and 3932036-CK461 as included in Appendix A of this document. The ESCPs 

detailed in this report give possible erosion and sediment controls that would need to be developed 

in more detail by the Contractor for the project. 

2 Site Description 

The TEM alignment runs generally west to east following the coast near Papamoa, changing 

direction inland to bypass Te Puke and link with the SH2 intersection near the Te Puke golf course. 

The topography is flat to gently undulating. This plan only relates to the drainage works required 

between Te Maunga and Domain Road. The catchments relevant to this ESCP include the 

Mangatawa, Wairakei, Arataki and Maranui catchments. In the current situation, most of the 

catchments drain to the Rangataua Bay via the Mangatawa drain. The proposed mitigation 

measures will provide the same discharge scenario during regular storm events. In major storm 

events water will spill over the motorway into the Maranui and Wairakei catchments. The Maranui 

catchment will drain to Rangataua Bay bypassing the treatment pond via a floodway corridor. 

This section of the TEM covered by this plan begins near the Baypark Stadium in Papamoa and 

follows the East Coast Main Trunk railway line (ECMT) parallel to the Papamoa residential suburb 

to the Domain Rd intersection with SH2. The total footprint of the site affected by these earthworks 

is approximately 10ha, of which excavation and fill are approximately balanced. 

2.1 Geology 

Geotechnical investigations and subsequent reports undertaken in 2006/07 identify that there are 

four geological units found within this length of the TEM alignment. These are summarised below: 

Beca // 1 April 2009 // Page 1 

3932036 // NZ1-1453076-10 0.10

• Peat – comprises organic material and, to varying degrees, mineral material. 

• Foredune sand – a series of sand blown ridges composed predominantly of fine to medium 

sand. 

• Alluvium – underlies and peat and foredunes, as well as being present at ground level. The 

alluvium is composed of variable normally consolidated silts, sands, clays, gravels, and 

carbonaceous material. 

• Fluvial Terrace - contains a wide variety of laterally and vertically variable materials including 

silts, sands, gravels, muds, and peats, inter-layered with airfall tephras (volcanic ashes). 

2.2 Ecology 

The Maranui wetland discharges to an existing special ecological site 13 (SES13) before 

discharging to Rangataua Bay. The site has been identified by Tauranga City Council as a 

significant natural area to be protected. Discharges from the work site to the wetland during 

construction are likely to have an adverse affect on the SES if no erosion and sediment controls are 

in place. As such works will be undertaken in a manner whereby the potential for sediment to enter 

the wetland will be mitigated with the use of erosion and sediment control proceedures similar to 

that set out in Section 4 and will remain consistent with EBOP Guideline No. 2001/03. 

The forebay of the stormwater treatment wetland will be installed prior to the start of the Maranui 

catchment earthworks to mitigate the effects of works on the receiving enviornment. The forebay 

will act to remove sediment from sediment laden flows entering the stormwater treatment wetland, 

treating dirty water before it enters the SES13. As such the potential to compromise the ecological 

significance of the SES13 shall be mitigated. 

In addition the wetland, low flowing waterways within the works site are likely to be an important 

habitat for fish during the spawning season; Whitebait in particular are likely to utilise the habitats 

available on site. The Lower Mangatawa Drain in particular has been identified as an area of 

significant ecological value and therefore no works will be undertaken within the Lower Mangatawa 

Drain, earthworks shall be limited to the surrounding floodplain only. Furthermore all site works will 

be undertaken in a manner whereby fish passage and habitat are not affected, in order that aquatic 

indigenous biodiversity and fish numbers are maintained. Works will be consistent with the 

objectives and policies set out in the Operative Regional Water and Land Plan. 

3 Construction Details 

3.1 Construction Methodology 

The construction of the TEM will be undertaken as a Design and Build process, whereby the 

Contractor will be responsible for developing the final design and construction of the project. The 

Contractor is responsible for the development and implementation of a detailed ESCP as with the 

rest of the alignment. 

The Contractor is required through the contract specifications to develop a series of plans to 

mitigate the effects of the project. These plans will include: 

• Erosion sediment control plan (ESCP) 

• Dust suppression plan 

• Environmental safety plan 

For the ESCP the Contractor’s construction methodology will be dependant on a number of factors, 

including design philosophy, resources available, fill material properties and supply rate, 


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embankment settlement rates, and the like. The consent process will set out the environmental 

bottom lines for this project that the Contractor will be required to adhere to. Therefore the 

methodology outlined below is a simplified summary of what may occur. 

As part of this application for the Mangatawa Drain and associated works four situations have been 

considered to show that a suitable ESCP can be developed during the detailed design phase to 

manage the effects of the works. Due to the varying terrain and contours, the ESCP for the 

construction of each of these elements should be considered separately, as the works will either 

occur at different times or each would have its own discrete mitigation measures. Erosion and 

sediment control measures are discussed in Section 4.2.1. 

3.1.1 Mangatawa Drain 

The Mangatawa Drain flows in a north-westerly direction alongside the south-western boundary of 

the TEM from Chainage 1050 to Chainage 6800. 

On the eastern side of Kairua Road, enclosed between the rail track and the motorway, a storage 

area will be created by excavating approximately 28,000m 3 from the drain. It is likely that some of 

this excavated material will be used for the 4,000m 3 of fill required to establish a 3 metre wide 

1 metre high bund at the top of the drain alignment along the northern side. Excess material will 

either be re-used elsewhere on site or appropriately removed off site. Further to this approximately 

100 – 200m 3 of excavation works will be undertaken to level the drain bed to a more uniform grade. 

3.1.2 Rail Bridge Embankment Stability 

Erosion of the Upper Mangatawa Drain banks adjacent to and beneath the rail bridge has been 

identified as a significant existing issue. Currently the drain alignment flows through two 90 degree 

bends when passing beneath the rail bridge. To mitigate the effects and potential for erosion along 

this section works will include improving the alignment of the drain as well as installing erosion 

control measures along both embankments and the drain invert. 

Earthworks associated with this work will mainly consist of excavation works required to realign the 

drain, however some fill works will be undertaken on the existing bends. The total volume of 

earthworks for this section of the drain is expected to be approximately 14,000m 3 . Gabion baskets, 

or similar, will be placed along the drain to protect the banks from erosion with reno mattresses 

along the bed of the drain to protect the gabion walls from under scour. Tied back concrete 

retaining walls will be constructed under the railway bridge to protect the bridge abutments. 

3.1.3 Culvert Extension 

a. Flood Bypass from Maranui to Mangatawa 

Approximately 3,000m 3 of excavation is required for the installation of two 2.1 metre diameter 

culverts under the TEM and railway track, linking the Maranui and Mangatawa Drain. The culverted 

bypass will discharge to the Mangatawa drain via a weir structure just upstream of the Mangatawa 

Lane Bridge. 

b. Sandhurst Culverts 

Approximately 2,000m 3 of excavation is required for the installation of a 70 metre long, 1.8 metre 

diameter culvert beneath the Sandhurst interchange. The culvert will be installed so as to allow 

flows from the Maranui swale beneath the interchange. 

c. Extension of Maranui Culverts 


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The longest section of culvert works is from the existing 1.8 metre Maranui culvert to the wetland. 

The Maranui culvert travels beneath SH2 and the rail track conveying stormwater from the existing 

swale discharging 120 metres upstream of the wetland area to an open drain. The existing culvert 

will be extended to the wetland where a concrete outlet structure will be constructed. The total 

extension is 80 metres long and will result in some earthworks to re-grade the drain but is expected 

to be no greater than 2,000m 3 . 

3.1.4 Lower Mangatawa Drain 

The Lower Mangatawa Drain flows in a south-westerly direction towards Rangataua Bay from 

Chainage 6800 to Chainage 6100. Works along the Lower Mangatawa Drain include reshaping of 

the existing floodplain and the installation of an earth bund along both sides of the drain. 

Along the Lower Mangatawa Drain construction will occur in two stages due to the large area of 

earthworks required. Due to the low lying nature of the lower reaches of the drain, and the risk of 

regular flooding, it is expected that work will progress from upstream down progressively improving 

fill to form the bund. As the bund is formed it will be stabilised as soon as practicable to protect it 

from storms and flooding. Due to the ecological significance of the drain (see Section 2.2) no works 

shall occur within the waterway. 

The Lower Mangatawa Drain construction is expected to require approximately 14,00m 3 volume of 

earthworks that will primarily be fill. Material excavated will either be reused for the proposed bund 

along the western and eastern side of the drain or appropriately removed off site. 


The existing wetland covers an area of approximately 3.2ha. In order to adequately treat stormwater 

from the TEM and surrounding area the wetland will be resized to expand the current treatment 

area. The total volume of earthworks proposed in this area is approximately 45,000m 3 . Stormwater 

treatment wetland works will be undertaken in two phases. Phase 1 includes the main body of 

works on the north-west section of the stormwater treatment wetland; this portion will receive 

stormwater primarily from the TEM Maranui swale as well as the Arataki and Papamoa residential 

areas. Phase 2 includes the smaller south-east section which will receive stormwater from the 

proposed Mangatawa Papamoa Blocks Incorporated (MPBI). The eastern section will eventually be 

linked with the main wetland area following Phase 2 works. NZTA is responsible for the initial stage 

of stormwater wetland works. The remaining works will be the responsibility of TCC and MPBI (see 

Section 4.2.5 for further detail). 

Stormwater treatment wetland works include extensive excavation works so as to establish a 

greater ponding area across the stormwater treatment wetland. The excavated material not used to 

reshape pond margins will be used to establish a bund along the eastern boundary of the Phase 1 

area or appropriately removed off site. This material is likely to generally consist of sands, gravels 

and silt. 

During construction of the TEM there is potential to take advantage of the proposed stormwater 

treatment wetland works and utilise some of the area as a temporary sediment retention pond. By 

constructing the proposed forebay of the stormwater treatment wetland prior to drainage works the 

potential effects of the project on the SES13 (see section 2.2 for further details) beyond the 

stormwater treatment wetland can be further mitigated. Diverting runoff from the works area through 

the forebay will remove sediment before water enters the main stormwater treatment wetland. 

Further treatment within the stormwater treatment wetland will result in relatively clean water 

discharging to the SES13. 


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3.2 Construction Sequence 

The typical sequence for the earthworks in fill areas is as follows: 

• Temporary access road and associated drainage; 

• Perimeter drains and bunds installed along the boundary to divert clean water and to contain 

runoff on site; 

• Erosion and sediment controls installed; 

• Placement and compaction of fill; 

• Stabilise with clean aggregate or hydroseed; 

• Install permanent drainage works. 

The typical sequence for the earthworks in cut areas is as follows: 

• Temporary access road and associated drainage; 

• Perimeter drains and bunds installed along boundary to divert clean water and to contain runoff 

on site; 

• Erosion and sediment controls installed; 

• Strip topsoil and stockpile for later reuse; 

• Excavate material and place in fill elsewhere on the project site; 

• Stabilise the exposed surface as soon as practical after excavation with either clean aggregate 

or hydroseed; 

• Install permanent drainage works. 

3.3 Permanent Stormwater Management 

Permanent stormwater management will be through the construction of open drains and swales to 

collect, treat and transport the water to the modified stormwater wetland system before discharging 

via existing discharge points. Where practicable permanent stormwater drainage will be installed 

and utilised for erosion and sediment control purposes during the construction period (e.g. as clean 

water diversions). 

4 Erosion and Sediment Control 

4.1 Principles of Erosion and Sediment Control 

The key principles to be employed for an ESCP are to undertake land disturbing activities in a 

manner that reduces the potential for erosion of bare soils to occur (erosion control) and, to employ 

treatment devices to treat all sediment laden water prior to discharging from the site (sediment 

control). The basic erosion and sediment control principles applicable to this project are as follows: 

1 Minimise disturbed areas and time of exposure: Only work those areas required for construction 

to take place. 

2 Progressively stabilise disturbed areas. 

3 Control erosion at the source. 

4 Keep onsite runoff velocities low. 

5 Install Perimeter Controls: Divert clean water away from areas of disturbance and divert runoff 

from areas disturbed to sediment control measures. 

6 Retain sediment on site. 


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7 Protect critical areas. 

8 Inspect and maintain control measures. 

4.2 Erosion and Sediment Control Measures 

To mitigate the effects of earthworks on the receiving environment (SES13) works shall be timed to 

coincide with periods of low flow and completed as quickly as practicable. If conditions are not 

suitable, such as periods of heavy rain, works shall be stopped. Further to this the programmed 

time of works shall avoid fish spawning seasons, especially in regard to sensitive species such as 

whitebait, as detailed by the Operative Regional Water and Land Plan. 

As water from the site discharges to a sensitive receiving environment, sediment control is of high 

importance and therefore works will be undertaken in line with best practice methods. The following 

plans, and subsequent Contractor’s plans, will be prepared in accordance with EBOP guidelines 

2001/03. 

This section gives a description of possible erosion and sediment controls that may be implemented 

by the earthworks Contractor on site. Due to the complexity of construction and the options 

available it is expected that the below methods will be superseded by a detailed ESCP prepared by 

the Contractor, and will be updated continuously as works on site progress. Any changes in plans 

will be reviewed and approved by Environment Bay of Plenty before works begin in the area 

covered by the plan. 

4.2.1 Mangatawa Drain 

Plan 3932036-C142 

While the volume of earthworks excavation associated with the Mangatawa Drain maintenance is 

only 200m 3 at most, the volume associated with the Kairua Road storage area within the 

Mangatawa Drain is approximately 28,000m 3 . Further to this there is approximately 4,000m 3 of fill 

works associated with the top spill bund alongside the drain. 

Clean water diversions will be placed along the northern boundary to divert clean flows from the 

working footprint and reduce the catchment requiring treatment. Due to the level of earthworks and 

the required work within the drain a decanting earth bund will be installed across the drain upstream 

of the Rail Bridge Embankment Stability works. Sediment laden flows from the upstream works will 

be treated by the decanting earth bund prior to discharging to the drain just upstream of the rail 

bridge. Ideally woks will be undertaken during periods of low flow so as to avoid the potential for 

effects on the downstream environment. 

During works in this area careful consideration will be given to the weather forecast and works will 

only commence if the following 24hour period indicates no significant rainfall. www.metvuw.co.nz 

will be utilised for this purpose. 

Further to this, works associated with the increased drain storage area east of Kairua Road will be 

segregated from the drain to reduce the potential for sediment to enter the waterway. This shall be 

through the use of either silt fence or sand bags depending on the level of flow within the drain. 

4.2.2 Rail Bridge Embankment Stability 

Plan 3932036-CK473 

To stabilise the drain embankment beneath the rail bridge a rock anchored concrete retaining wall 

shall be constructed. The space for construction beneath the bridge is limited and as such only 

small equipment and machinery will be used. Due to the nature of the works and the potential for 


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concrete contamination as well as sediment issues the works will be undertaken in two stages. 

Each stage will utilise the existing rail bridge columns so as to segregate the flow of water to one 

side (alternating as each stage is complete). Using this method will mean that the drain can 

continue to flow without being compromised by concrete or sediment contamination. Daily 

maintenance and house keeping activities will be of high importance during the stages of works, 

excess concrete will be removed off site immediately so as to avoid the potential for any spillage 

and adverse ecological effects. 

In addition to the works beneath the rail bridge, the drain profile will be realigned with gabion 

baskets and rino mattresses to create a stable cross-section profile 100m above and below the 

bridge. Earthworks associated with this realignment shall begin upstream and move downstream. 

While the ecological value of the Mangatawa Drain is not as significant as the Lower Mangatawa 

Drain (see Section 2.2) and working within the waterway is permitted, it is important to separate 

clean water and sediment laden flows so as to avoid any downstream effects. The work area shall 

be segregated from the flow of water so that earthworks activities can be undertaken in a manner 

whereby sediment is controlled and prevented from entering clean water. This shall be achieved 

through staging works and using sand bags or similar to separate the works area from the drain. 

Clean water will be pumped around the works area where required. 

During works in this area careful consideration will be given to the weather forecast and works will 

only commence if the following 24hour period indicates no significant rainfall. www.metvuw.co.nz 

will be utilised for this purpose. 

During the drain realignment works machinery will be limited to the dry stable areas above the 

embankment and shall not be positioned within the waterway. Gabion baskets shall be constructed 

of durable, inert materials and shall be filled with clean material free of clay, soil, mud or other fines. 

Material excavated from the dam embankments to create the improved alignment shall be used for 

filling the redundant 90 degree bends. Any excess material shall be reused elsewhere on site or 

appropriately removed off site. 

4.2.3 Culvert Extension 

a. Flood Bypass from Maranui to Mangatawa 

The volume of excavation required for the installation of the Maranui to Mangatawa bypass is 

3,000m 3 . Works will begin at the Maranui end of the bypass and move towards the Mangatawa 

Drain. To avoid clean water entering the open site the Maranui opening to the proposed culvert will 

be dammed; as such clean water will back up the culvert to the existing swale where, in the event of 

a storm, it can be adequately stored until works are complete. 

As the works move towards the Mangatawa Drain sediment controls will need to be installed to 

avoid the adverse effects of sediment associated with the outlet construction. Due to the size of the 

outlet and sensitivity of the Mangatawa Drain a works area within the drain will be segregated from 

the flow of water. By installing sheet piling or similar around the works area the drain can continue 

to flow without being compromised by sediment laden flows. Works will be undertaken in a 

cofferdam like environment. 

Upon completion of the bypass and outlet the dam and sheet pilling can be removed, allowing clean 

water to flow through the system when necessary. 


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. Sandhurst 

The installation of the Sandhurst culvert includes 2,000m 3 of excavation. The Maranui swale 

entering the culvert will be blocked off so as to avoid clean water entering the dirty works site. 

During rainfall events water will back up in the swale where it will be stored. Clean water diversions 

will be in place so no clean water will enter the site. Upon completion of the culvert installation the 

Maranui swale will be reconnected and clean water can continue to flow towards the wetland. 

c. Extension of Maranui Culverts 

The extension to the Maranui culvert includes 2,000m 3 of excavation. During works the drain will 

likely continue to convey clean water from the existing highway. To avoid clean water entering the 

open site the existing culvert will be dammed; as such clean water will back up the existing swale 

where it can adequately be stored until works are complete. Upon the completion of the culvert 

extension the dam shall be removed and water will return to flowing through the culvert to the 

stormwater treatment wetland. 

4.2.4 Lower Mangatawa Drain 

Plan 3932036-CK467A 

Plan 3932036-CK467A illustrates perimeter controls and sediment treatment devices that may be 

used. It shows the different sections of the drain that are to be constructed and gives the 

approximate area that will be worked. 

Given the area of earthworks required along the drain; works will be undertaken in stages. Stage 1 

will include an area of approximately 3ha on the west side of the drain. Clean water diversions will 

be placed along the northern boundary to divert clean flows from the working footprint and reduce 

the catchment requiring treatment. A stabilised earth bund will be installed along the length of the 

northern embankment of the existing drain so as to divert sediment laden flows away from the drain. 

A sediment retention pond will be installed in the lower south west corner of the works area to treat 

sediment laden flows from the open works area. Treated water will be discharged to the drain. A silt 

fence will extend around the boundary of the ecological wetland area so that any water entering the 

ecological area from the site will be treated by the fence. 

Stage 2 also covers an area of approximately 3ha along the eastern side of the drain. Stage 2 

works include batter reshaping. Clean water diversions will be installed to divert clean flows from 

the working footprint and reducing the catchment that requires treatment. As per the west side a 

stabilised earth bund will be installed along the length of the northern embankment of the existing 

drain so as to divert sediment laden flows away from the drain. A sediment retention pond will be 

installed in the lower south west corner of the works area so as to treat sediment laden flows from 

the open works area. Treated water will be discharged to the drain. 

Stabilisation of the batters using hydroseed or other approved methods will be undertaken as works 

are completed. 

4.2.5 Stormwater Treatment Wetland 

Plan 3932036-CK461 

Plan 3932036-CK461 gives perimeter areas for stages of works and sediment treatment devices 

that may be used. There are three stages of works for Phase 1 of the stormwater treatment 

wetland; where as Phase 2 can be undertaken in a single stage of works. NZTA will be responsible 

for the works associated with Stage 1 of Phase 1 as outlined below. Tauranga City Council will be 

responsible for the Stage 2 and 3 works of Phase 1, with MPBI responsible for Phase 2. 


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Pahse 1 consists of the western section of the proposed works and includes the existing wetland. 

The majority of the area is currently dry vegetated land making earthworks possible without the 

need for clean water diversions. Completing the works in three stages will minimise the potential for 

sediment to enter the clean water system by maintaining a separation between the open earthworks 

areas and existing channels. 

Stage 1 consists mainly of forebay works and requires a volume of 5,500m 3 of earthworks. 

Excavated material will be utilised in the eastern boundary bund or temporarily stockpiled on the 

existing vegetated areas to allow for drainage. Stockpiles will be positioned away from the clean 

water areas. Water will continue to enter the existing wetland via the open drain along the eastern 

boundary. A silt fence will be installed between the forebay works and open drain so as to avoid 

sediment from the works mixing with clean water flows. Upon completion of the forebay, water shall 

be diverted to the west of the silt fence so that works can be undertaken on the existing open drain. 

Undertaking the forebay works first will allow for the existing pond to be used as a temporary 

sediment retention pond. The forebay will be utilised to remove sediment from dirty water entering 

the wetland from the Maranui culvert. This approach will reduce the potential for adverse affects of 

the project on the SES13 beyond the stormwater treatment wetland as potentially sediment laden 

water from the Marunui catchment works will be treated. 

The total volume of earthworks required for Stage 2 and Stage 3 works is approximately 20,000m 3 . 

Plan 3932036-CK461 shows the perimeter of Stage 2; just under half of which is area to be 

excavated. Material excavated from the area will be reused as fill material for a bund along the 

boundary of the stormwater treatment wetland and the SES13; excess material not used for batter 

shaping will be appropriately stockpiled and removed off site. A silt fence will be installed around the 

eastern perimeter of Stage 2 prior to works beginning. All machinery will be kept out of the 

waterway on dry land and stable areas within the works site and excavated materials will be placed 

well away from the waterways. 

Prior to Stage 3 works beginning the existing wetland pond located in the centre of the Stage 3 area 

will need to be drained. To allow the wetland system to continue functioning and to drain the central 

area, stage 2 works will be opened and a temporary dam structure will be constructed in the 

existing channel as shown on plan 3932036-CK461. Water entering the system will now flow 

around the western channels of the constructed stormwater treatment wetland, away from the 

centre. This will allow for stage 3 earthworks to be undertaken in a clean water free section. To 

further mitigate the effects of sediment entering the clean water, the Stage 2 silt fence along the 

eastern boundary will remain and an additional silt fence will be constructed along the northern 

boundary of Stage 3 during the works. 

As the stormwater treatment wetland will continue to be operational, outlet works will be undertaken 

during periods of extreme low flows and any water discharged shall be pumped around the works if 

necessary. 

As the eastern boundary bund from the Phase 1 works will remain in place, Phase 2 earthworks can 

be undertaken without disturbing the stormwater treatment wetland. Phase 2 includes a volume of 

24,000m 3 of earthworks; more than half of which is area to be excavated. Material excavated from 

the area will be reused as fill material for a bund constructed along the boundary of the stormwater 

treatment wetland and the SES13 as well as for fill material along the central ridge of the Phase 2 

area. Excess material not used for bund shaping will be appropriately removed off site. 

4.2.6 Ingress/Egress Points 

A stabilised entranceway, with a wheel wash if required, will be constructed at the ingress/egress 

points to help in the removal of sediment before reaching the public road. If earth is tracked onto 


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the public road it will be removed by the Contractor using appropriate methods (e.g. sweeper/sucker 

truck). 

4.2.7 Dust suppression 

A dust management plan will be developed by the Contractor prior to the start of works and shall 

include details of the volume of water that is likely to be required, number of watering trucks 

required and the location and number of wheel washing facilities. During the dryer summer months 

dust control measures will be of high priority to avoid nuisance affects. 

In accordance with EBOP guidelines water should be applied at a rate of at lest 5mm/day 

(50m 3 /hectare) during dry periods. It is highly likely that water for use as a dust suppressant will be 

sourced from a municipal reticulated water supply rather than from on-site storage. In this instance 

written confirmation will be required from the territorial authority for the use of municipal water. 

4.3 Erosion and Sediment Control implementation Sequence 

The anticipated implementation sequence for the erosion and sediment controls is as follows: 


• Construction of perimeter controls such as clean water diversions for works; 

• Installation of decanting earth bund; 

• Installation of Kairua Road controls; 

• Drain and storage area earthworks; 

• Stabilise completed areas as soon as practicable 

• Remove decanting earth bund. 

Rail Bridge Embankment Stability 

• Construction of perimeter controls such as dams and clean water diversions for works; 

• Embankment excavation; 

• Gabion basket and Reno Mattress installation; 

• Rail Bridge works; 

• Fill corners; 

• Progressively stabilise completed areas as soon as practicable. 

Culvert Extension 

• Construction of clean water diversions; 

• Pipe the existing drains; 

• Install clean water diversions around outlet construction; 


Lower Mangatawa Drain 

• Construction of perimeter controls such as silt fences and runoff diversions for Stage 1 works; 

• Installation of Stage 1 decanting earth bund; 

• Stage 1 earthworks; 

• Stabilise completed Stage 1 areas as soon as practicable; 

• Construction of perimeter controls such as silt fences and runoff diversions for Stage 2 works; 


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• Installation of Stage 2 decanting earth bund; 



Stormwater Wetland 

• Construction of perimeter controls such as silt fences; 



• Construction of dam weir; 

• Diversion of clean water entering wetland through the new Stage 2 channels; 


• Construction of outlet; 

• Progressively stabilise completed areas as soon as practicable; 

• Construction of perimeter controls such as silt fences and bund in Phase 2; 

• Phase 2 earthworks; 

• Open Phase 2 to Phase 1. 

5 Monitoring and Maintenance 

Erosion and sediment control measures will be installed, monitored and maintained throughout the 

works until the site is stabilised. The table below outlines inspection and maintenance requirements 

for erosion and sediment controls that are to be implemented in this ESCP. 

Control Type Inspection and Maintenance Requirements Frequency 

Silt fence • Check that silt fences are toed in correctly. 

• Check for tears and other damage. 

• Any areas of collapse, decomposition or ineffectiveness 

are to be replaced immediately. 

• Remove silt build ups when bulges develop or when 

deposition reaches 50% of the silt fence height. 

Diversion 

bunds and 

channels 

Sediment 

Retention 

Pond 

Decanting 

Earth Bund 

• Ensure they are in the correct place (clean water 

diverting flows away from the work area and sedimentladen 

flows directed to sediment treatment devices). 

• Inspect for signs of scouring or collapse and repair 

immediately if required. 

• Remove any material that may have accumulated. 

• General inspection 

• Clean out sediment build up in forebay 

• Check outlet for blockages 

• Check level spreader 

• Check discharge points for scour 

• Check that outlet is not blocked 

• Remove built up sediment from around base 

Daily 

Daily 

As required 

As required 

Daily 

Daily 

As required 

Weekly 

As required 

Weekly 

Weekly 

Weekly 

Daily 

As required 

Regularly and 


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• Make sure bund is stabilised 

• Check spillway for obstructions 

• Ensure no erosion at outlet 

Weir Dam • Check that dams are adequately connected in to 

embankment with use of sandbags. 

• Check for accumulated sediment. 

• Check discharge points for scouring. 

Stabilised 

Entranceway 

Stabilising 

Areas 

• Install further armouring (sand bags) as required. 

• Inspect any structure used to trap sediment from the 

stabilised entranceway. 

• Check that all stabilised areas have 80% cover. 

• Identify areas that require stabilisation. 

after rain 

Regularly 

Regularly and 

after rain. 

After each 

rainfall event. 

As works 

progress (a 

minimum of 

once per week). 

A further aspect of monitoring should be that associated with weather forecast monitoring. So as to 

avoid unstable weather conditions www.metvuw.co.nz should be utilised so critical works can be 

planned during a suitable weather window when adverse sediment and erosion effects can be 

avoided. 


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Appendix A 

Erosion and Sediment 

Control Plan Drawings

APPENDIX 14 - 

Regional Water and Land Plan 

Activity Status, Rules, Policies and 

Objectives

Activity Status Mangatawa Drain 

1.1 Land and Soil Disturbance Activities 

The proposed Earthworks and Vegetation clearance activities are Discretionary as the total volume 

of earthworks exceeds permitted activity limits and the proposed vegetation clearance does not 

meet permitted activity conditions related to replanting with trees. 

Rule 1C - Earthworks and Quarries 

The disturbance of land and soil as a result of earthworks or a quarry, where the activity: 

1. Is not permitted by a rule in this regional plan; and 

2. Is not a controlled activity under a rule in this regional plan, and 

3. Is not a restricted discretionary activity under a rule in this regional plan; 

Is a discretionary activity 

Assessment Criteria 

When assessing resource consent applications under this rule, Environment Bay of Plenty will have 

particular regard to, but not be limited to, the following provisions: 

Objective 4, 5, 9, 17, 19, 21, 31, 32, 34 

Policy 5, 14, 15, 17, 18, 20, 21, 51, 54 

Method 12, 19, 20, 56, 60, 124 

Explanation/Intent of Rule 

To control earthworks and quarries that present a high risk to the environment, and where it is 

appropriate to assess the effects of the activity within the resource consent application process. 

Rule 2C - Land and Soil Disturbance by Vegetation Clearance 

The disturbance of land and soil resulting from vegetation clearance, where the activity: 

1. Is not permitted by a rule in this regional plan, and 

2. Is not a controlled activity under a rule in this regional plan, and 

3. Is not a restricted discretionary activity under a rule in this regional plan; 

Is a discretionary activity. 



particular regard to, but not be limited to, the following provisions: 

Objective 4, 5, 9, 17, 19, 21, 31, 34 

Beca // 22 December 2008 // Page 1 

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Policy 5, 14, 15, 17, 18, 20, 21, 51, 54 

Method 13, 20, 21, 56, 60, 124 

1.2 Discharges to Water and Land 

The discharges proposed in this application range from restricted discretionary to discretionary. As 

these discharges will operate during a flood event they will contribute to flooding and by definition 

have discretionary activity status. The proposed discharge at Rangataua Bay is a restricted 

discretionary activity due to a greater than 125l/s flow rate. 

Rule 37 - Discharges to Water or Land 

Any: 

1. Discharge of a contaminant to water. 

2. Discharge of water to water. 

3. Discharge of a contaminant onto or into land in circumstances which may result in the 

contaminant (or any other contaminant emanating as a result of natural processes from that 

contaminant) entering water. 

4. Discharge of a contaminant from any industrial or trade premises onto or into land. 

That is not: 

(a) Permitted by a rule in this regional plan. 

(b) Permitted by a rule in any other Bay of Plenty regional plan. 

(c) Prohibited by a rule in this regional plan. 

(d) Restricted discretionary status by a rule in this regional plan. 

(e) Controlled status by a rule in this regional plan. 

Is a discretionary activity 

This activity is also subject to the requirements of the rules in section 9.4. 

All discharges to surface water that are discretionary under this rule will be assessed gainst the 

Water Quality Classification of the receiving water body (refer to Schedule9 and the Water 

Classification map). 

Resource consent applicants who seek to exceed the relevant Water Quality Classification 

standards must provide evidence in their application to demonstrate how the adverse effects of the 

proposed activity will be avoided, remedied or mitigated to be consistent with Objective 13. 

Cross Reference RWLP Dec 2002, Pg34 

Objective 13 The water quality in rivers and streams is maintained or improved to meet the 

Water Quality Classifications set in the Water Quality Classification Map, and the following 

environmental outcomes: 

(a) Natural State (Lake) Water Quality Classification - the natural quality of the water shall not 

change. 


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(b) Natural State (River) Water Quality Classification - the natural quality of the water shall not 

change. 

(c) Managed State (Lake) Water Quality Classification - the water quality in the lake shall not 

deteriorate. 

(d) Aquatic Ecosystem (Bay of Plenty) Water Quality Classification – water quality shall be sufficient 

to support diverse and healthy aquatic ecosystems. 

(e) Contact Recreation Water Quality Classification - water quality shall be sufficient to allow contact 

recreational uses. 

(f) Water Supply Water Quality Classification - water quality shall be sufficient to allow for municipal 

water supply purposes, while recognising water treatment may still be required. 

(g) Drains with Ecological Values Water Quality Classification - water quality shall be sufficient to 

support aquatic ecosystems, while recognising that aquatic ecosystems in such areas are limited. 

(h) Regional Baseline Water Quality Classification - water quality shall not deteriorate. 

Advisory Note 

2. If a resource consent applicant is unable to avoid, remedy or mitigate adverse effects on the 

environment, and does not meet Objective 13, the resource application is likely to be publicly 

notified and/or consent may be declined. 


To allow Environment Bay of Plenty to assess the adverse effects of any discharge of contaminants 

or water to the environment that is not otherwise addressed by other regional rules. The resource 

consent process is an appropriate means of assessing such effects. Rule 37 applies to, but is not 

limited to, comprehensive catchment discharges consents for stormwater, discharges from 

contaminated sites, and large scale discharge of contaminants from trade and industrial premises 

(including waste disposal discharges). 



particular regard to, but not be limited to, the following provisions as appropriate to the nature of the 

discharge: 

Objective 4, 5, 6, 11, 13, 14, 15, 16, 20, 23, 25, 26, 27, 30, 31, 32, 33, 34 

Policy 5, 11, 14, 15, 17, 18, 19, 20, 21, 38, 42, 44, 45, 47, 48, 50, 51, 53, 54, 55, 56 

Method 13, 17, 18, 20, 21, 56, 60, 77, 109, 110, 111, 112, 113, 114, 118, 119, 120, 127, 135, 138, 

139, Water Quality Classification Map, Schedule 9 

1.3 Damming and Diversion of Water 

These are the core proposed activities in this application that are primarily designed to provide 

better flood protection. While reducing the flooding effects the activity does not comply with Rule 

44A and by reference Rule 30 an therefore is a Discretionary activity 

Rule 48 Discretionary – Damming or Diversion of Water 

The damming or diversion of water that is: 


// NZ1-1349440-2 0.2

1. Not permitted by a rule in this regional plan, and 

2. Not restricted discretionary status under a rule in this regional plan, and 

3. Not prohibited by Rule 49, 

Is a discretionary activity. 


To allow Environment Bay of Plenty to assess any damming or diversion activity that will have 

greater than minor adverse effects on the environment, on a case by case basis through the 

resource consent process. 



particular regard to, but not be limited to, the following provisions as appropriate to the source of the 

proposed water take: 

Objective 4, 5, 6, 8, 42, 47, 55, 73, 75 

Policy 5, 11, 14, 15, 17, 18, 19, 20, 21, 65, 81, 83, 84, 100, 133, 134 

Method 13, 17, 18, 20, 21, 56, 60 

1.4 Activities in the beds of rivers streams and lakes 

The Mangatawa Drain is considered to be a “Land Drainage Canal” or a “modified water course” as 

defined by the RWLP Dec 2002, Definition of Terms, Pg 436. 

Land Drainage Canal – a modified watercourse that is part of a land drainage scheme. 

For the purposes of this regional plan the term ‘Land Drainage Canal’ is limited to the following, 

(g) ….. Bruce R/SH2, Mangatawa-SH2, Railway, Farmlands; 

However as these works will include new capital works, Rule 71 applies and the works are 

Discretionary. 

Rule 71 Discretionary – Activity in the Beds of Streams, Rivers and Lakes 

Unless provided for by another rule in this regional plan, the: 

1. Use, erection, reconstruction, placement, alteration, extension, removal, or demolition of any 

structure or part of any structure in, on, under, or over the bed of a stream, river or lake, 

2. Excavation, drilling, tunnelling or other disturbances to the bed of a stream, river or lake, 

3. Introduction of planting of any plant or any part of any plant in, on, or under the bed of a stream, 

river or lake, 

4. Disturbance, removal, damage or destruction of any plant or any part of any plant in, on, or 

under the bed of a stream, river or lake, 

5. Deposition of any substance in, on, or under the bed of a stream, river or lake, 


// NZ1-1349440-2 0.2

6. Reclamation or drainage of the bed of a stream, river or lake, Is a discretionary activity. 


To allow Environment Bay of Plenty to assess the adverse environmental effects of activities in the 

bed of a stream, river or lake on a case by case basis, where the activity is likely to cause more 

than minor effects. In relation to deposition of substances, this rule includes, but is not limited to, 

gravel storage, and the deposition of debris and tree trimmings. This rule also applies to existing 

reclamations that are not otherwise authorised. The consent duration for reclamations of the bed of 

a river, stream or lake is unlimited under section 123 of the Act. 



particular regard to, but not be limited to, the following provisions as appropriate to the type of 

activity: 

Objective 4, 5, 6, 8, 55, 56, 58, 59, 61 

Policy 5, 11, 14, 15, 17, 18, 19, 20, 21, 98, 99, 100, 101, 104, 106, 107, 108,110 

Method 13, 17, 18, 20, 21, 56, 60, 205, 206, 209, 224, Schedule 1, 2, 3 

Placing of culverts in the proposed activities ranges from Restricted Discretionary to permitted for 

the purposes of this consent it will be assessed using restricted discretionary criteria. 

Rule 59D Restricted Discretionary– Culverts where fill height is greater than 2.5 metres 

The use, erection, reconstruction, placement, alteration or extension of a culvert in, on, under or 

over the bed of a river, stream, or lake where the structure: 

1. Is not located within an urban area or settlement, or within one kilometre upstream of any 

urban area or settlement; and 

2. Is not located where the adjacent land slope is greater than 35º; and 

3. Is not located in a wetland; and 

4. The fill height over the culvert is greater than 2.5 metres; 

Is a restricted discretionary activity subject to the following conditions: 

(a) The culvert shall be constructed to allow the passage of the 1% AEP (1 in 100 year return) event 

by heading up to a maximum of 0.5 metres below the road surface, and the passage of the 10% 

AEP event without heading up. 

(b) The culvert embankment shall be comprised of suitable soils free of wood, humus and other 

organic matter. The embankment shall be well compacted in uniform layers not exceeding 

300mm loose depth to achieve a compaction of at least 95 percent of maximum dry density. 

(c) The activity shall not prevent the passage of migrating fish. 

(d) No works shall be undertaken in the bed of a water body listed in Schedule 1D between 1 May 

to 30 August. 

(e) No works shall be undertaken in the bed of a water body listed in Schedule 1A between 15 

August and 15 October. 


// NZ1-1349440-2 0.2

(f) The resource consent applicant shall supply: 

(i) A report confirming that the culvert embankment shall be comprised of suitable soils free of 

wood, humus and other organic matter; and that the embankment shall be well compacted in 

uniform layers not exceeding 300 mm loose depth to achieve a compaction of at least 95 percent 

of maximum dry density. 

(ii) A geotechnical report affirming that the culvert embankment will be of safe batter slope, and 

constructed to avoid failure. 

Environment Bay of Plenty restricts its discretion to the following matters: 

(a) Measures to avoid, remedy or mitigate the adverse effects of the structure on: 

(i) Erosion or land instability, including erosion protection works. 

(ii) The passage of fish. 

(iii) Aquatic ecosystems, including indigenous biodiversity. 

(iv) Property owned or occupied by another person, including flooding or ponding. 

(v) Natural water flow and flood flows. 

(vi) Other structures. 

(vii) Navigation in navigable rivers and lakes. 

(viii) Houses, assets and other activities downstream of the culvert, which are at risk of the culvert 

failure. 

(b) Measures to minimise the duration and extent of bed disturbance. 

(c) Measures to avoid or mitigate vegetation, soil, slash construction material or other debris being 

deposited in the surface water body, or placed in a position where it could readily enter or be 

carried into a water body. 

(d) Maintenance of the culvert. 

(e) Construction standards, including ensuring the structure can not break free and cause a 

blockage or erosion. 

(f) Number of culverts in the cross-sectional area of the stream. 

(g) Monitoring requirements. 


To provide for culverts where the fill height in the crossing structure needs to be assessed fully by 

Environment Bay of Plenty. 


// NZ1-1349440-2 0.2

APPENDIX 15 - 

Legal Descriptions of Land Parcels 

Affected by Construction

FULL_APP 

Papamoa 2No8B2B2 

Papamoa 2No8B2B1 

Lot 2 DPS 34073 

Papamoa 2No8A 

Sec 1 SO 392281 

Pt Lot 1 DPS 86263 

Papamoa 2No8B2C 

Pt Papamoa 4B2 

Pt Lot 2 DP 34461 

Pt Lot 1 DP 34461 

Lot 1 DPS 28790 

Lot 1 DPS 78971 

Lot 180 DP 324280 

Sec 7 SO 344199 


Lot 26 DP 358304 

Lot 1 DPS 30609 


Lot 1 DPS 82167 

Lot 1 DP 320271 

Lot 3 DP 320271 

Lot 3 DP 323089 

Papamoa 2No5D1 

Pt Papamoa 2No5A 

Pt Papamoa 2No6B2B 

Lot 2 DP 320271 

Lot 2 DP 326676 

Mangatawa 2B2A 

Mangatawa 4B2 

Lot 2 DPS 31917 

Mangatawa 2A2 

Mangatawa 9B3B2 

Mangatawa 8C1 


Pt Mangatawa 2B1 



Pt Mangatawa Papamoa 

Pt Mangatawa 10 

Mangatawa 2B (Roadway) 

Pt Papamoa 2No9A 

Lot 56 DPS 70217 

Lot 55 DPS 70217 

Lot 66 DPS 70217 

Pt Mangatawa 2 


Mangatawa 3A 


Lot 189 DP 324280 

Lot 190 DP 324280 

Lot 1 DP 326676 

Lot 3 DPS 59938 

Lot 1 DPS 64336 

Pt Mangatawa Papamoa 

Lot 2 DPS 73505 

Lot 53 DPS 70217 

Lot 2 DPS 73503

Path: P:\393\3932036\TGI\55_ProjectsAndWorkspaces\02_Wor\Planning\MaunagatawaAffectedParcelsRev5.WOR Created Date: 07 April 09 Printed Date: 07 April 09 Author:OK Job # :3932036 

Scale: 1:15,000 at A2 

Contains Crown Copyright Data. Crown Copyright Reserved. 

Map intended for distribution as PDF document. 

Scale may be incorrect when printed. 

This map contains data derived in part or wholly from sources other than Beca, and therefore, 

no representations or warranties are made by Beca as to the accuracy or completeness of this information. 

± 

Mangatawa Directly Affected Parcels 

Figure 1 

Legend 

Property Boundaries 

Mangatawa Directly Affected Parcels

APPENDIX 16 - 

Existing TCC Discharge Consent 

Nº 60061

32 Harington Street 

PO Box 903, Tauranga 3140, New Zealand 

T: +64 7 578 0896 // F: +64 7 578 2968 

E: info@beca.com // www.beca.com 

Environment BOP 

PO Box 364 

Whakatane 

3 September 2009 

Attention: Dudley Clemens 

Dear Dudley 

Mangatawa Drain Flood Bypass and TEL Stormwater AEE 

Further to our discussions with you and in view of Jo Bain’s email on the 04/09/09, we confirm the 

return of the Phase 2 wetland earthworks activity to construct the wetland in our joint application for 

Resource Consent submitted on behalf of NZ Transport Agency and Tauranga City Council. We 

seek to alter the earthworks volumes in application and wish to make the following alterations to the 

lodged AEE. 

Page 16 

The last two lines should read: 

“The total volume of earthworks required to be undertaken is approximately between 

61,000m 3 – 80,000m 3 for the TEM component of the works only. See section 9.2.” 

Page 71 

The second bullet point should have the last sentence deleted, i.e. it should read: 

“The total volume of earthworks required for TCC works in the proposed stormwater 

treatment wetland is 16,000m 3 – 20,000m 3 .” Deleted – This will be the subject of a future 

application. 

Section 9.2, page 89 

The second paragraph should read: 

“The total volume of earthworks required to be undertaken is approximately 61,000m 3 – 

80,000m 3 .” 

Section 9.2, page 90 

Insert after the first paragraph the following text: 

Our Ref: 3932036 

NZ1-2111967-3 0.3

Page 2 

3 September 2009 

“The construction of the Phase 2 and 3 components of the stormwater treatment wetland will 

be subject to the same mitigation measures employed by the rest of the TEL project as 

described above.” 

Appendix 10 

Drawing Nº’s 3932036-CK460 Rev A and 3932036-CK460 Rev A are to be replaced with new 

Drawing Nº’s 3932036-CK460 Rev C and 3932036-CK460 Rev B 

Please use this letter and attached drawings as a reference addendum to the main application. If 

you have any queries please contact the undersigned on 5771129. 

Please note that the lodged AEE contains all the relevant environmental assessment for earthworks 

for phase 2 and 3 of the wetland construction. 

Yours sincerely 

Christine Ralph 

Technical Director 

on behalf of 

Beca Infrastructure Limited 

Direct Dial: +64-7-577 1129 

Email: christine.ralph@beca.com 

Copy 

TCC, NZTA 

Our Ref: 3932036 

NZ1-2111967-3 0.3

32 Harington Street 

PO Box 903, Tauranga 3140, New Zealand 

T: +64 7 578 0896 // F: +64 7 578 2968 

E: info@beca.com // www.beca.com 

Environment Bay of Plenty 

PO Box 364 

Whakatane 

New Zealand 

19 June 2009 

Attention: Dudley Clemens 

Dear Dudley 

Mangatawa Stormwater Joint Application No. 65435 

Please find enclosed a Cultural Impact Assessment (CIA) requested by the landowner, Mangatawa 

Papamoa Blocks Incorporated (MPBI), who has the land adjacent to the lower Mangatawa drain 

leading to the harbour. This information is supplementary to the consultation record in the main 

application and is relevant for this landowner only. 

The assessment identified a waahi tapu area near the lower Mangatawa drain works and has 

resulted in the kaumatua of Nga Potiki undertaking to determine the extent of the site. The issue 

identified in the CIA did not relate to the flooding of the land but was associated with movement and 

excavation of soil in this area (see assessment for details). 

A summary of the main works required along the lower Mangatawa drain include: 

• Redistribution of existing drain spoil, piled next to the existing drain. Appendix 10 of the 

main application shows the cross sectional details (Drawing 3932036 ck469 Rev A) of the 

proposed works. 

• Filling of adjacent industrial zoned land to give flood protection to the land for future 

develop-ability and re-contouring the lower Mangatawa drain riparian margin 

• Re-vegetation and landscaping of the re-contoured lower Mangatawa drain margin for 

recreational purposes. 

In general terms, the CIA does not oppose these activities, however in relation to the extent of the 

waahi tapu site and the works required on or near it, these industrial protection works may be 

required to be moved westwards to avoid the extent of the waahi tapu site and accommodate the 

hapu’s wishes. 

NZTA is facilitating this process through consultation with MPBI. 

Yours faithfully 

Christine Ralph 

Technical Director - Planning 

on behalf of 

Beca Infrastructure Ltd 

Direct Dial: +64-7-577 1129 

Email: christine.ralph@beca.com 

Copy 

Michael Parsonsen 

Our Ref: 3932036 

NZ1-1842494-6 0.6

2. Mangatawa catchment consents for earthworks, storm water ...

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