Some ESC design features have been included in the Golder and BECA reports, for example clean water diversion sizing. In this case, where requirements vary between , the more stringent adopted from the outset. 2.1. Surface Facilities Area Refer to ESCP-WR-001-01 and ESCP-WR-001-02 The surface facilities include noise bunds, car parking, detention pond, effluent disposal field, pipe storage/stockpiling area, offices, amenities, and related facilities. The Detention Pond, designed by BECA, will be built to service the earthworks within the Surface Facilities and broader disturbed farm areas. A super silt fence will be installed below the footprint of the pond to capture any runoff during the construction of this pond. A cut area may need to be established to provide suitable material for the construction of the Detention Pond. If required, a sediment retention pond (SRP-1) will be constructed below the cut area to capture and treat runoff from this cut area. A clean water diversion bund will be constructed above the cut area and dirty water diversions will direct sediment laden runoff to SRP-1. The Detention Pond has a design capacity of 5,000m3 and will act as a sediment retention pond for the approximately 5ha Surface Facilities Area during construction and for the life of mining. In accordance with TR2009/02 a sediment retention pond (SRP) constructed for this area would require a total volume of 1,500m3 (3% of the contributing catchment area). In this case the detention pond has an excess of 3,500m3 of storage volume. Refer to BECA engineering report for Detention Pond design details. During the earthworks phase the Detention Pond will be fitted with a concrete manhole, 300mm outlet pipe and 3x T-bars. The concrete manhole will need to be weighted down. Once the earthworks are completed, the facility areas will be sheeted with aggregate. Landscaped areas, including the noise bunds (if remaining in place) will be topsoiled and stabilised with grass seed and mulch. The T-bars will be removed from the Detention Pond manhole, and discharge orifice and weir installed as per BECA design details. 2.2. Wharekirauponga Underground Mine Refer to ESCP-WR-002-01 Access to the Willows Portal will be via a new Mine Access Road. This access road will also provide a link with the Willows Rock Stack. A Collection Pond, designed by Golder, will be constructed to service the enabling earthworks associated with the access road construction (and Willows Rock Stack – refer Section 2.3 below). The Collection Pond will be constructed as per design, but in the initial stages and enabling works phase, will be used as a sediment retention pond. A super silt fence will be installed below the footprint of the Collection Pond to capture any runoff during the construction of this pond. Given the relatively high permeability of the gravels that underlie the Collection Pond footprint, Golder anticipate that the Collection Pond will require an artificial liner to avoid seepage of mine affected water into the adjacent wetland and Mataura Stream. If required, it is likely that the liner will be installed immediately following the construction of the Collection Pond. The Collection Pond has a design capacity of 18,700m3. The access roads and Willows Rock Stack areas have a combined area of approximately 6ha. In accordance with TR2009/02 a sediment retention pond (SRP) constructed for this area would require a total volume of 1,800m3 (3% of the contributing catchment area). In this case the Collection Pond has an excess of 16,900m3 of storage volume. During the enabling earthworks phase the Collection Pond will be fitted with a concrete manhole, 450mm outlet pipe and four T-bars. The
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