convey the clean water downstream, subsoil drainage may be directionally drilled through the base of the Willows Rock Stack. The subsoil drainage pipes will discharge the clean water downstream of the rock stack. Some sections of open trenching to install subsoil drainage may also be required. Material placed in the Willows Rock Stack is planned to start being used as tunnel backfill from approximately Year 6 with complete removed of the Rock Stage by Year 10. 2.4. Topsoil Stockpile Refer to ESCP-WR-003-01 An area of approximately 2-3ha will be used to stockpile topsoil generated from the project. Clean water diversions will be installed around the top of the stockpiling area. A sediment retention pond (SRP-1) will be constructed near the base of the topsoil stockpile which will capture and treat runoff from the stockpile as well as runoff during the construction of the Magazine Access Road. The maximum contributing catchment area is 3ha and this will be managed on site to ensure that no more than 3ha is directed to this pond at a time. The stockpile will be progressively stabilised with grass seed and hay mulch. SRP-1 will be retained to manage runoff quality during topsoil recovery and site rehabilitation. 2.5. Magazine Storage Area and Access Road Refer to ESCP-WR-003-01, ESCP-WR-003-02, and ESCP-WR-003-03, The establishment of the Magazine Storage Area (Explosives Magazine) requires earthworks across a total area of approximately 1.2ha. An existing farm race will be upgraded to an 885m long, 6mwide access road to service the Magazine Storage Area. Majority of the earthworks associated with the Magazine Access Road upgrade will be cut into the bank on the northern side of the access road, with some areas of fill required below the access road. Clean water diversions will be installed around the Magazine Storage Area to direct upper clean water catchment away from the earthworks area. An existing farm culvert installed beneath the farm track will be upgraded to a 450mm diameter pipe to cater for the flows from the upper clean water catchment. A sediment retention pond (SRP-3) will be constructed below the Magazine Storage Area to capture majority of the runoff during its construction. A small area to the northeast of the Magazine Storage Area will not fall to the SRP, including the fill area. It is anticipated that a super silt fence or decanting earth bund (DEB) could be utilised for this section of the work. Preference will be super silt fence due to the steep slopes and gully system below this area. Once the construction of the Magazine Storage Area is complete it will be sheeted with aggregate. SRP-3 will either remain in place as a water collection pond or decommissioned. The Magazine Access Road will be constructed in two sections (in terms of erosion and sediment control methodology). The first section of approximately 350m fromWillows Road requires minimal earthworks. This section will be completed as a cut and cover operation where the road will be cut to grade and stabilised with aggregate within the same day. Batters formed above the road will be progressively hydroseeded / hydro mulched. The second section of work up to the Magazine Storage Area requires more earthworks to widen the road and provide suitable access. As the road is cut out a roadside table drain will be formed. Runoff from the road will be sloped/cambered towards the table drain and will flow down to SRP-2 constructed below the topsoil
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