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

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• 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, Beca // 1 April 2009 // Page 2 3932036 // NZ1-1453076-10 0.10
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 Beca // 1 April 2009 // Page 3 3932036 // NZ1-1453076-10 0.10
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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:
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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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Page 233 and 234: 2.2 Hydrological Assessment 2.2.1 C
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Page 237 and 238: Table 7 - 2% AEP Storm Event Top Sp
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Page 245: Appendix A Mangatawa Drain Layout P
Page 249: Appendix C Runoff Hydrographs
Page 255: Appendix E Proposed Lower Mangatawa
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Page 275 and 276: Report Tauranga Eastern Motorway -
Page 277: 1 Introduction This report describe
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Page 287 and 288: • Installation of Stage 2 decanti
Page 289: Appendix A Erosion and Sediment Con
Page 295 and 296: Activity Status Mangatawa Drain 1.1
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Page 299 and 300: 6. Reclamation or drainage of the b
Page 301 and 302: APPENDIX 15 - Legal Descriptions of
Page 303 and 304: Path: P:\393\3932036\TGI\55_Project
Page 311 and 312: 32 Harington Street PO Box 903, Tau
Page 313: 32 Harington Street PO Box 903, Tau
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