84 • Foundation soil conditions and shape of the natural depression that allows for geotechnical stability, a thicker layer of weak clay founding soils in Tributary 1 was a key reason for selecting Tributary 2. • Size of natural depression was large enough to accept the required rock storage volume. • Cost of locating elsewhere. We understand that a single WRS option was preferred over two facilities to manage volume requirements, mainly due to additional disturbance footprint required for rehabilitation, and to best minimise effects on surface water bodies. The haulage gradient and distance from the portal has a twofold effect on cost first for initial placement and secondly when reclaimed as backfill material for the WUG (WSP Golder 2022). 14.4.2.3 Water management WSP Golder (2022) sets out the water management for the WRS with the collection and drainage of clean water around the WRS and flows discharging back into existing tributary below the WRS. Clean water channels will collect surface water from the north and south margins of the WRS, and the channels are likely to be natural incised channels armoured with rip rap as required. We set out the indicative design of offset and clean water channels in Appendix 11. These channels are not formed as natural streams and are not accounted for as part of any offset for loss of streams. 14.4.2.4 Tributary 2 rehabilitation We note that in this circumstance, the loss of tributary 2 is temporary, but the effects management and stream offset calculations have assumed a permanent loss of this watercourse. Accordingly, an offset is proposed that will meet the potential ecological value assessed through an appropriate ecological offset model to deliver a no net loss outcome. We emphasise that the rock stack is expected to have a 10-year lifespan and following that there will be a period of rehabilitation of the tributary. WSP Golder (2022) set out that once the rock is reclaimed, the WRS footprint topsoil can be replaced, harrowed (where gradients allow machinery) and seeded to return to an end use of grazing pasture. Monitoring and maintenance will be required for a period until deemed a selfsustaining good pasture cover is established. Due to steepness of the natural terrain WSP Golder (2022) recommends that grazing in the first two winters is avoided, and only light weight animals allowed in the other months (weaners or sheep) to prevent soil damage from pugging and soil compaction. A rehabilitated stream channel will be reinstated, and the collection sumps removed. Fencing to exclude stock will be installed and riparian planting undertaken. The rehabilitation of the tributary (including ensuring fish passage is provided for) will result in an improved and enhanced catchment compared to that at present, i.e., the tributary will also meet its potential ecological value assessed through an appropriate ecological offset model. Combined, the proposed offset and the proposed rehabilitation of tributary 2 will result in a net gain in freshwater ecological benefit for the Willows Road Farm component of the project. 14.4.2.5 Effects Management As outlined above, the NPS-FM requires that the loss of river extent and values is avoided, unless there is a functional need for the activity in that location, and the effects management hierarchy is applied to any effects of that activity (section 3,24, NPS-FM). As the temporary loss of stream length cannot be avoided or mitigated (for the reasons for this set out above), an ecological offset is proposed, as per the effects management hierarchy, and the details are set out below and in more detail in Appendix 9. We have calculated an
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