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 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. Status: Final Page 107 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 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. Status: Final Page 108 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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NZ Transport Agency and Tauranga Ci
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Page 64 and 65: NZ Transport Agency and Tauranga Ci
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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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