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 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 ⇓ Rangataua Bay from Maranui catchment Current 11,680 14.0 9.6 Proposed 5,840 9.3 5.3 Change 5,840 ⇓ 4.7 ⇓ 4.3 ⇓ Rangataua Bay from MPBI Industrial Current 22,600 1.8 6.8 Proposed 13,560 23.5 13.6 Change 9,040 ⇓ 21.7 ⇑ 6.8 ⇑ Status: Final Page 85 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 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. Mangatawa Flood Bypass 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 TEM Roadway Stormwater 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 Status: Final Page 86 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 43: NZ Transport Agency and Tauranga Ci
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Page 116: APPENDIX 1 - Drawing 3932036 ck301R
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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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