B-1 - Area 1, Coromandel Forest Park – Assessment of Environmental Effects 74 Regolith water and interflow are not expected to change as a consequence of any potential dewatering of the Rhyolite rock mass. Plants which access water from the Regolith soils are also not expected to be adversely affected. 5.3.5 Ground Settlement An assessment of ground settlement is included in GWS (2022) and EGL (2022), copies of which are included in Part H of these application documents. The total settlement from the Dual Tunnels and decline out to the WUG are expected to be in the order of 10 to 100 mm with any tilt likely to be very small. There are no buildings near to the Dual Tunnels which could be affected by settlement. Total settlement around the ventilation shafts is expected to be in the order of 50 to 300 mm. These settlements would have no adverse effect on the forest area in which they would be located. Total settlement of up to 300 mm to 1000 mm could be expected in the area of the WUG site, however, due to the hilly terrain at the site, ground settlement of this magnitude is not expected to have any material effect on the environment, including stream flows. The flattest stream grade is approximately 1 in 30 over a 500 m length at the north end of the East Graben Vein. For a maximum settlement of 1000 mm, occurring over a distance in the order of 200 m (i.e. estimated minimum distance from maximum to no settlement, based on the dewatering depths), this would result in a shallowing or steepening of grade in the order of 1 in 200. For a stream at 1 in 30, a 1 in 200 grade change is very minor. 5.3.6 Conclusion OGNZL has committed to manage its mining activities so that they have no measurable effect on surface water flows within streams in the CFP. Various expert reports have been commissioned which demonstrate how that will be achieved using relatively conventional management techniques for mining activities where groundwater inflows are expected. A range of conditions are proposed which provide a detailed roadmap for how the principles described in those reports will be applied to ensure an acceptable outcome is achieved in respect of effects on surface water. Achieving this outcome also means that water within the soil regolith which plants access will not be adversely affected. 5.4 EFFECTS ON AQUATIC ECOLOGY An assessment of the potential effects on aquatic ecology values in Area 1 is provided in Boffa (2022a), a copy of which is provided in Part H of these application documents.
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