concrete manhole will need to be weighed down. A dirty water diversion drain will be constructed along the lower side of the access track to convey runoff to the Collection Pond. Where practical, clean water diversions will be constructed to direct upslope clean water away from the working areas. At several locations culverts will need to be installed to allow clean water to flow under access tracks and continue downslope. Golder have provided indicative clean water diversion sizing details, where requirements vary between the ESC designs, the more stringent adopted from the outset. Topsoil is proposed to be placed on the uphill side of the Mine Access Road. Once completed, the topsoil stockpiles will be stabilised with grass seed and hay mulch. Once formed, the Mine Access Road will be sheeted with aggregate. During the enabling earthworks, the Collection Pond will serve purpose as a sediment retention pond, discharging treated sediment laden water to the receiving environment. Once the enabling earthworks are complete (including the Willows Rock Stack enabling works detailed below), the Collection Pond will receive mine water that may contain PAF material. Water collected with then report to the Water Treatment Plant. 2.3. Willows Rock Stack Refer to ESCP-WR-002-01 The Willows Rock Stack will be established to stockpile approximately 876,000m3 of rock excavated during tunnelling for the underground mine. In terms of the erosion and sediment control measures proposed for the Willows Rock Stack, specific measures are proposed for the construction of the Collection Pond and enabling earthworks during the setup phase of the Rock Stack before any PAF material is placed. Refer to the Willows Rock Stack and Surface Facilities Geotechnical Assessment, prepared by Golder for specific staging and construction details. Initially, a super silt fence will be installed below the footprint of the Collection Pond to enable the construction of the Pond. Sediment laden runoff (non-acid forming) during the enabling earthworks phase will be directed to the Collection Pond for treatment prior to being discharged to the receiving environment. As noted above, the Collection Pond has a design capacity of 18,700m3 and will be utilised as a sediment retention pond for the enabling earthworks. The access roads and Willows Rock Stack areas have a combined area of approximately 6ha. Once the Willows Rock Stack is set up to receive PAF material, then the water conveyed to the Water Treatment Plant and the operational requirements commence. The Willows Rock Stack will be a staged development based on the OGNZL underground development rock movement schedule commencing in Year 1 and progressing to a total design capacity of 876,000m3 in Year 5. An access road will provide a link between the mine portal and the Willows Rock Stack. A second access road will be constructed at the base of the Willows Rock Stack. Roadside table drains will be constructed to link the main access road to the Collection Pond and the smaller Willows Rock Stack Seepage Collection Pond (approximate volume 500m3) to the main Collection Pond (approximate volume 18,700m3). Clean water diversions will be constructed around Willows Rock Stack to direct upper slope clean water away from the rock stack, where possible. Golder have provided indicative clean water diversion sizing details, where requirements vary between the ESC designs, the more stringent adopted from the outset. Multiple springs are located within the Willows Rock Stack footprint. In order to tap into these springs and
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