Transpower New Zealand Limited
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Appendix F Ecological Assessment Transpower Ltd REPORT Hairini - Mount Maunganui Trans mission Line Realignment Marine Ecological Assessment Prepared for TranspowerTr an sp ow er (NewNe w Zealand) Limited PreparedPr ep ar ed byy TonkinTo nk in & Tayloray lo r Ltd Date SeptemberSe pt em be 20201717 JobJo b NumberNu mb er 26752.222026 75 2. 22 Distribution: Transpower (New Zealand) Limited 1 PDF copy Tonkin & Taylor Ltd (FILE) 1 PDF copy Table of contents 1 Introduction 1 2 Description of proposed activity 2 2.1 Tower 118 removal 2 2.2 Pole 128 replacement with Pole 128A 3 2.2.1 Access track 3 2.2.2 Works area 3 2.2.3 Tree removal 3 2.3 Temporary wiring sites 4 3 Ecological assessment methods 4 3.1 Tower 118 4 3.1.1 Benthic survey 4 3.1.2 Habitat classification 7 3.1.3 Coastal birds survey 7 3.2 Pole 128/128A and SEA 25 7 3.3 Wiring sites 7 4 Results 7 4.1 Tower 118 7 4.1.1 General habitat description 7 4.1.2 Areas of ecological value 7 4.1.3 Habitat type classification 8 4.1.4 Benthic ecology 8 4.1.5 Threatened benthic marine species 13 4.1.6 Kaimoana species 13 4.1.7 Papaka 13 4.1.8 Coastal birds 13 4.1.9 Wiring site near Pole 33D 13 4.2 Pole 128/128A and SEA 25 14 4.2.1 SEA 25 description and values 14 4.2.2 Values in and around Pole 128/128A and associated access track 14 4.2.3 Values in and around the wiring site and tree clearance areas 15 5 Assessment of effects on the environment 15 5.1 Effects assessment framework 15 5.2 Effects of Tower 118 removal works 16 5.2.1 Ecological effects on benthic fauna of area near Tower 118 16 5.3 Effects on kaimoana species 17 5.4 Effect on surrounding habitats present in Rangataua Bay 17 5.5 Effects on coastal seabirds 17 5.6 Effects on SEA 25 and adjacent habitats 18 5.6.1 Effects on wetland birds 19 5.6.2 Habitat disturbance effects 19 5.7 Summary of ecological effects 20 6 Ecological mitigation summary 21 6.1 Tower 118 21 6.2 Works within and around SEA 25 21 7 Conclusion 22 8 Applicability 23 Appendix A : Drawings Appendix B : EcIA guidelines Appendix C : Benthic Fauna Appendix D : Mitigation Location Plan Tonkin & Taylor Ltd September 2017 Hairini - Mount Maunganui Transmission Line Realignment - Marine Ecological Assessment Job No: 26752.2220 Transpower (New Zealand) Limited 1 1 Introduction Transpower (New Zealand) Limited (Transpower) is proposing to realign a section of the Hairini- Mount Maunganui (HAI-MTM) A and B 110 kV transmission lines in Tauranga. These two lines are both Single Circuit lines on poles. The A line was commissioned in 1958, while the B line was commissioned in 1995. The section of A and B lines proposed to be realigned is located on both sides of Rangataua Bay, Tauranga Harbour. This work will involve: The removal of HAI-MTM-A118 (known as Tower 118) that is located in the Coastal Marine Area (CMA). The removal of Tower 118 will result in one aerial span crossing the harbour, connecting two new monopoles on either side; and The replacement of Pole 128 with a new Pole 128A immediately adjacent to it and which is located adjacent to a Category 2 Special Ecological Area (SEA) 25, as described in the Tauranga City Plan (see Figure 1.1 for locations). It is noted that the Proposed Regional Coastal Environment Plan also includes an Indigenous Biodiversity Area B located within the overall boundaries of SEA25. Temporary wiring sites will be established as part of the realignment works to enable new conductors to be pulled through the transmission line poles. Proposed wiring site locations are shown on Figure 1.1 below and on the drawings provided as Appendix A. The temporary wiring site located near to Pole 128 and is located within SEA 25. Figure 1.1: Aerial photograph showing ecological assessment locations (Source: Google Earth) Transpower has requested Tonkin & Taylor Limited (T+T) to undertake ecological assessments to understand the impacts of the proposed realignment works on ecological values at the tower/pole removal/replacement as described above and the temporary wiring sites proposed within SEA25 and adjacent to the CMA. This assessment will support the resource consent applications for the project. Tonkin & Taylor Ltd September 2017 Hairini - Mount Maunganui Transmission Line Realignment - Marine Ecological Assessment Job No: 26752.2220 Transpower (New Zealand) Limited 2 This assessment: Describes the existing ecological values at Tower 118 and Pole128A, and the surrounding areas that may be affected by the works; Determines the ecological significance of the impacted areas; Assesses the actual and potential effects of proposed activities on the ecology of the works areas; and Identifies appropriate measures to avoid, remedy, or mitigate adverse effects. 2 Description of proposed activity This section describes the parts of the overall Hairini-Mount Maunganui transmission line realignment relevant to this ecological assessment. 2.1 Tower 118 removal Transpower is proposing to remove Tower 118 in its entirety, including the foundations to below the level of the existing seabed. The location of Tower 118 is shown on Figure 1.1 and on AECOM Drawing 60438334-3 included in Appendix A. It is proposed to remove the bulk of the above ground portion of the tower by contractors dismantling and/or cutting portions of the tower, which will then be removed off site by helicopter and disposed of appropriately. This methodology eliminates the need for temporarily storing portions of the tower on the sea-bed and therefore minimises adverse effects. The above methodology would remove the bulk of the steel portion of the tower, leaving short sections of the remaining vertical members (legs) and associated concrete foundations. The remaining leg sections and concrete foundations would then be removed to a level around 500 mm below existing seabed level using a barge based methodology. The following is a proposed methodology for the removal of the foundations for Tower 118 and has been provided to Transpower by Bay Underwater Services Ltd. The works methodology will be confirmed by the contractor prior to works commencing. We understand that any substantive departure from the methodology assessed may result in a variation of resource consent being required. In summary, when the pylon has been cut down to just above the sea bed, sand will be excavated down to approximately 800 - 1,000 mm around each leg. This will allow the vertical legs to be cut off at 500 mm below seabed level. The legs will be supported by a barge based HiAb then cut and transported to shore for landfill disposal. Specific steps include: The contractor will have a certified work boat and skipper onsite at all times; All gear to be used will be set up and tested; If it is low tide as many pre-cuts as possible will be completed; At high tide, the HiAb barge will be stationed alongside the pylon base; Strops will be secured to the pre-cut members to support them for the final cuts; Once they are cut they will be loaded onto the HiAb barge; The HiAb will continue to hold the members being cut; When the tide is getting too low for the barge to operate effectively, the barge will back off the sand bank and take the sections of pylon back to the load out area onshore (a formal boat ramp, location to be confirmed); The pylon sections will be loaded onto a HiAb truck and transported to a land fill for disposal; Tonkin & Taylor Ltd September 2017 Hairini - Mount Maunganui Transmission Line Realignment - Marine Ecological Assessment Job No: 26752.2220 Transpower (New Zealand) Limited 3 When all of the horizontal members have been removed the Dive team will excavate around the legs. Each leg will be excavated down to approximately 800 – 1,000 mm below sea level, to allow for it to be cut at 500 mm below sea level. This will be done using a 4 inch hydraulic trash pump; The hydraulic power pack runs on Bio oil that is approved as environmentally friendly; The material will be excavated from the hole through a 4 inch hose to approximately 6 m away from the existing pylon base; The hose will be underwater at all times and is anticipated to result in a minimal sediment plume or water discolouration, as the material is only being transferred from one place underwater to another; After the excavation has been completed, the HiAb will be connected to the leg; The diver will cut through the member using a hydraulic ring saw; The member will be loaded onto the barge; This will continue until all of the legs have been removed; The excavation will be refilled once the legs have been removed. The sand that has been removed from the excavations will be re-pumped into the holes to leave the seabed as flat as possible; and All gear and any debris will be removed from site. 2.2 Pole 128 replacement with Pole 128A 2.2.1 Access track The replacement of Pole 128 will require an access track to be formed and a works area to be cleared within an area of existing vegetation, and adjacent to an existing Special Ecological Area (SEA 25), also referred to in the Proposed BoP Regional Coastal Environment Plan as Indigenous Biodiversity Area (IBDA) B23.