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

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NZ Transport Agency and Tauranga City Council Mangatawa Drain Flood Bypass and TEM Stormwater AEE 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): Status: Final Page 47 April 2009 Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE
NZ Transport Agency and Tauranga City Council Mangatawa Drain Flood Bypass and TEM Stormwater AEE • 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. Status: Final Page 48 April 2009 Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE
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Mangatawa Drain Flood Bypass and TE
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APPENDIX 1 - Drawing 3932036 ck301R
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APPENDIX 3 - Drawing 3932036 ck119
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APPENDIX 5 - Bioresearches Report:
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APPENDIX 7 - Archaeological Assessm
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ARCHAEOLOGY B.O.P. HERITAGE CONSULT
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2 INTRODUCTION Project Background T
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4 ARCHAEOLOGICAL LANDSCAPE Previous
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6 U14/1708 & 1709 Figure 3. Cadastr
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8 Figure 6. Part ML 8133 showing Pt
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10 Hungahunga & Toroa A further ton
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12 APRIL 2008 ARCHAEOLOGICAL SURVEY
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14 Historic Places Act In addition
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APPENDIX 8 - Hydraulic Modelling: M
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Hydraulic Modelling: Mangatawa Drai
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undertake investigations into the d
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Discharge to Papamoa Beach To disch
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• Riparian planting adjacent to t
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2.2 Hydrological Assessment 2.2.1 C
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The Maranui catchment area in the m
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Table 7 - 2% AEP Storm Event Top Sp
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These results include climate chang
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3.3 Maintenance Work in Mangatawa D
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stormwater from the Maranui catchme
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Appendix A Mangatawa Drain Layout P
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Appendix C Runoff Hydrographs
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Appendix E Proposed Lower Mangatawa
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APPENDIX 10 - Drawings 3932036 ck46
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APPENDIX 12 - Drawing 3932036 ck227
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Report Tauranga Eastern Motorway -
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1 Introduction This report describe
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embankment settlement rates, and th
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3.2 Construction Sequence The typic
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concrete contamination as well as s
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Pahse 1 consists of the western sec
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• Installation of Stage 2 decanti
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Appendix A Erosion and Sediment Con
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Activity Status Mangatawa Drain 1.1
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(b) Natural State (River) Water Qua
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6. Reclamation or drainage of the b
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APPENDIX 15 - Legal Descriptions of
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Path: P:\393\3932036\TGI\55_Project
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32 Harington Street PO Box 903, Tau
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32 Harington Street PO Box 903, Tau
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