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

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7 Protect critical areas. 8 Inspect and maintain control measures. 4.2 Erosion and Sediment Control Measures To mitigate the effects of earthworks on the receiving environment (SES13) works shall be timed to coincide with periods of low flow and completed as quickly as practicable. If conditions are not suitable, such as periods of heavy rain, works shall be stopped. Further to this the programmed time of works shall avoid fish spawning seasons, especially in regard to sensitive species such as whitebait, as detailed by the Operative Regional Water and Land Plan. As water from the site discharges to a sensitive receiving environment, sediment control is of high importance and therefore works will be undertaken in line with best practice methods. The following plans, and subsequent Contractor’s plans, will be prepared in accordance with EBOP guidelines 2001/03. This section gives a description of possible erosion and sediment controls that may be implemented by the earthworks Contractor on site. Due to the complexity of construction and the options available it is expected that the below methods will be superseded by a detailed ESCP prepared by the Contractor, and will be updated continuously as works on site progress. Any changes in plans will be reviewed and approved by Environment Bay of Plenty before works begin in the area covered by the plan. 4.2.1 Mangatawa Drain Plan 3932036-C142 While the volume of earthworks excavation associated with the Mangatawa Drain maintenance is only 200m 3 at most, the volume associated with the Kairua Road storage area within the Mangatawa Drain is approximately 28,000m 3 . Further to this there is approximately 4,000m 3 of fill works associated with the top spill bund alongside the drain. Clean water diversions will be placed along the northern boundary to divert clean flows from the working footprint and reduce the catchment requiring treatment. Due to the level of earthworks and the required work within the drain a decanting earth bund will be installed across the drain upstream of the Rail Bridge Embankment Stability works. Sediment laden flows from the upstream works will be treated by the decanting earth bund prior to discharging to the drain just upstream of the rail bridge. Ideally woks will be undertaken during periods of low flow so as to avoid the potential for effects on the downstream environment. During works in this area careful consideration will be given to the weather forecast and works will only commence if the following 24hour period indicates no significant rainfall. www.metvuw.co.nz will be utilised for this purpose. Further to this, works associated with the increased drain storage area east of Kairua Road will be segregated from the drain to reduce the potential for sediment to enter the waterway. This shall be through the use of either silt fence or sand bags depending on the level of flow within the drain. 4.2.2 Rail Bridge Embankment Stability Plan 3932036-CK473 To stabilise the drain embankment beneath the rail bridge a rock anchored concrete retaining wall shall be constructed. The space for construction beneath the bridge is limited and as such only small equipment and machinery will be used. Due to the nature of the works and the potential for Beca // 1 April 2009 // Page 6 3932036 // NZ1-1453076-10 0.10
concrete contamination as well as sediment issues the works will be undertaken in two stages. Each stage will utilise the existing rail bridge columns so as to segregate the flow of water to one side (alternating as each stage is complete). Using this method will mean that the drain can continue to flow without being compromised by concrete or sediment contamination. Daily maintenance and house keeping activities will be of high importance during the stages of works, excess concrete will be removed off site immediately so as to avoid the potential for any spillage and adverse ecological effects. In addition to the works beneath the rail bridge, the drain profile will be realigned with gabion baskets and rino mattresses to create a stable cross-section profile 100m above and below the bridge. Earthworks associated with this realignment shall begin upstream and move downstream. While the ecological value of the Mangatawa Drain is not as significant as the Lower Mangatawa Drain (see Section 2.2) and working within the waterway is permitted, it is important to separate clean water and sediment laden flows so as to avoid any downstream effects. The work area shall be segregated from the flow of water so that earthworks activities can be undertaken in a manner whereby sediment is controlled and prevented from entering clean water. This shall be achieved through staging works and using sand bags or similar to separate the works area from the drain. Clean water will be pumped around the works area where required. During works in this area careful consideration will be given to the weather forecast and works will only commence if the following 24hour period indicates no significant rainfall. www.metvuw.co.nz will be utilised for this purpose. During the drain realignment works machinery will be limited to the dry stable areas above the embankment and shall not be positioned within the waterway. Gabion baskets shall be constructed of durable, inert materials and shall be filled with clean material free of clay, soil, mud or other fines. Material excavated from the dam embankments to create the improved alignment shall be used for filling the redundant 90 degree bends. Any excess material shall be reused elsewhere on site or appropriately removed off site. 4.2.3 Culvert Extension a. Flood Bypass from Maranui to Mangatawa The volume of excavation required for the installation of the Maranui to Mangatawa bypass is 3,000m 3 . Works will begin at the Maranui end of the bypass and move towards the Mangatawa Drain. To avoid clean water entering the open site the Maranui opening to the proposed culvert will be dammed; as such clean water will back up the culvert to the existing swale where, in the event of a storm, it can be adequately stored until works are complete. As the works move towards the Mangatawa Drain sediment controls will need to be installed to avoid the adverse effects of sediment associated with the outlet construction. Due to the size of the outlet and sensitivity of the Mangatawa Drain a works area within the drain will be segregated from the flow of water. By installing sheet piling or similar around the works area the drain can continue to flow without being compromised by sediment laden flows. Works will be undertaken in a cofferdam like environment. Upon completion of the bypass and outlet the dam and sheet pilling can be removed, allowing clean water to flow through the system when necessary. Beca // 1 April 2009 // Page 7 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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undertake investigations into the d
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Discharge to Papamoa Beach To disch
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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 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
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Page 275 and 276: Report Tauranga Eastern Motorway -
Page 277 and 278: 1 Introduction This report describe
Page 279 and 280: embankment settlement rates, and th
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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
Page 297 and 298: (b) Natural State (River) Water Qua
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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