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

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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 Beca // 17 March 2009 // Page 9 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 Beca // 17 March 2009 // Page 10 3932036 // NZ1-1604459-15 0.15 Rev A
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Mangatawa Drain Flood Bypass and TE
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NZ Transport Agency and Tauranga Ci
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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:
Page 205 and 206: APPENDIX 7 - Archaeological Assessm
Page 207 and 208: ARCHAEOLOGY B.O.P. HERITAGE CONSULT
Page 209 and 210: 2 INTRODUCTION Project Background T
Page 211 and 212: 4 ARCHAEOLOGICAL LANDSCAPE Previous
Page 213 and 214: 6 U14/1708 & 1709 Figure 3. Cadastr
Page 215 and 216: 8 Figure 6. Part ML 8133 showing Pt
Page 217 and 218: 10 Hungahunga & Toroa A further ton
Page 219 and 220: 12 APRIL 2008 ARCHAEOLOGICAL SURVEY
Page 221 and 222: 14 Historic Places Act In addition
Page 223 and 224: APPENDIX 8 - Hydraulic Modelling: M
Page 225 and 226: Hydraulic Modelling: Mangatawa Drai
Page 227 and 228: undertake investigations into the d
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Page 233: 2.2 Hydrological Assessment 2.2.1 C
Page 237 and 238: Table 7 - 2% AEP Storm Event Top Sp
Page 239 and 240: These results include climate chang
Page 241 and 242: 3.3 Maintenance Work in Mangatawa D
Page 243 and 244: stormwater from the Maranui catchme
Page 245: Appendix A Mangatawa Drain Layout P
Page 249: Appendix C Runoff Hydrographs
Page 255: Appendix E Proposed Lower Mangatawa
Page 263: APPENDIX 10 - Drawings 3932036 ck46
Page 272: APPENDIX 12 - Drawing 3932036 ck227
Page 275 and 276: Report Tauranga Eastern Motorway -
Page 277 and 278: 1 Introduction This report describe
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Page 281 and 282: 3.2 Construction Sequence The typic
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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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