5 - Shear key excavations. Shear key excavation is likely to be 50m wide (at base) and 3-7m deep. - Progressively line impoundment area with a geomembrane. - Construct Collection Ponds. - Progressively raise embankment/facility. - Establish permanent uphill diversion drain. - Complete site infrastructure and full site establishment. The ESC measures are shown on design drawings provided in Appendix A. Updated detailed ESC drawings will be prepared prior to these works commencing. 2.1. Stage 1 Refer to ESCP-TSF3-001-01, ESCP-TSF3-001-02, ESCP-TSF3-001-03 and ESCP-TSF3-001-04. Stage 1 will involve initial preparatory activities (e.g., clearing of vegetation), progressive construction of the ESC measures, establishment of the stockpiles, realignment of the Ruahorehore Stream and Paleo Gully undercut. Stockpiles Three stockpiling areas are proposed to the east and southeast of the TSF3. Stockpiles 1 and 2 are proposed to be located to the southeast of the TSF3. Stockpile 1 covers an area of approximately 5.5ha to contain up to 225,000m3 of material with a max crest height of RL130. Stockpile 2 covers approximately 12ha to contain up to 2,700,000m3 with a max crest height of RL160. A third stockpile, located to the north of Stockpiles 1 and 2 will cover an area of 1.5ha and contain 23,000m3 of material at a max crest height of RL172. Note, this stockpile is shown in the Stage 5 drawings (ESCP-TSF3005-01 and ESCP-TSF3-005-02). Perimeter bunds will be constructed around the footprint of the stockpiles to divert runoff to the SRPs as well as diverting clean water from above catchment areas away from the fill areas. SRPs will be used to treat runoff from each of the stockpiles. The catchment area for SRP-TSF3-01 will slightly exceed the maximum recommended catchment area in TR2009/02 at approximately 5.1ha for Stockpile 1. SRP-TSF3-01 has been designed with a minimum storage volume of 1,650m3 to provide for a maximum contributing catchment area of 5.5ha. SRP-TSF3-02 has been designed to capture runoff from the entire 12ha Stockpile 2 area. This SRP has been designed with a total volume of 4,000m3, exceeding the minimum storage requirement of 3% of the contributing catchment area. Dual manholes and outlet pipes will need to be incorporated into the SRP, as well as eight T-bars to maintain the recommended discharge rate of 3L/sec/ha. Additional weight will be required to be placed in the base of the manholes to keep them securely in place in the event that the pond fills with water. The manholes will also be built into the pond’s internal embankment if possible. While the SRP has been designed to cater for the full 12ha catchment area, it is not likely that the entire area will be ‘open’ at one time. The stockpile will be progressively stabilised to minimise the amount of open area and sediment load of runoff flowing to the SRP. SRP-TSF3-03 will be constructed within a natural low point on the southwestern side of Stockpile 2. A clean water diversion will be required to divert clean water around the footprint of this pond. This 2ha SRP will be constructed to enable the earthworks associated with the stockpile, while not all runoff will flow to SRP-TFS3-
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