90 15.0 Services Trench: Ecological Effects and Management 15.1 Construction method The Service Trench will be constructed using appropriately sized excavation plant. Excess spoil will be removed off site and shoring methods will be employed if the service trench exceeds a depth of 1.5 m. Directional boring may be used to install services under SH25 to a yet to be determined invert level. High-density polyethylene services will be continuously welded along the route and placed into the trench on bedding sand and then covered. Detectable tape will be installed above the services prior to backfilling with spoil and compacting. Erosion and sediment control measures will also be employed over the construction footprint and will follow the Erosion and Sediment Control Plan (OGNZL 2021). 15.2 Management of the services trench The services occur as welded sections of high-density polyethylene of high strength and durability. An updated Water Management Plan will detail the operational management and maintenance of the services. We understand that leak detection will be part of the pipe construction design (pressure sensors). 15.3 Effects on tributary streams As set out above, the service corridor crosses two unnamed tributary streams (Sites 4 and 5, Appendix 13) as it approaches the Waihi operations. The services will be contained within a pipeline set out across or under the respective stream. The crossings will result in activities within the riparian margin and on the banks of the streams, but no activity will take place within the stream beds. Erosion and sediment management will be applied to the trenching operations and riparian planting is proposed to replace riparian vegetation that is cleared for the operation. Accordingly, effects on the tributaries will be negligible. 15.4 Effects on Favona Wetland The service continues and passes close to the Favona Wetland. We have established that the Favona Wetland is a natural wetland under the NPS-FM and therefore subject to the provisions of the NESF. The route of the services trench avoids the wetland but passes within 100 m of the wetland boundary. No earthworks will occur within Favona Wetland, or within 10 m of the wetland. Erosion and sediment controls will ensure that and sediment intrusions into the wetland will be minimised. Our understanding of the construction methodology is that the services will be embedded within sand in the trench and then re-covered with the original and same soil material. We do not expect this method to result in any changes to the hydrological conditions surrounding or within the Favona Wetland.
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