Supporting Technical Assessments

REV DATE REVISION DETAILS APPROVED 0 17.06.22 Draft for review. Project WAIHI NORTH Title Erosion and Sediment Control Plan Tailings Storage Facility 3 – Stage 5 Drawn ZW Checked MP Drawing No. ESCP-TSF3-005-02 Sheet No. 12 NOTES 1. All erosion and sediment controls will be installed and maintained in accordance with the Waikato Regional Council Technical Report 2009/02 ‘Erosion and Sediment Control Guidelines for Soil Disturbing Activities’ (TR2009/02). 2. Completed areas to be stabilised in accordance with TR2009/02. 3. All erosion and sediment control measures will be inspected weekly by the site foreman. 4. Site monitoring will be undertaken before and immediately after rain as well as during heavy rainfall events. Any required maintenance or improvements to control measures will be undertaken immediately. Construction Methodology Continued construction of Permanent Uphill Clean Water Diversion Drain. First section of the permanent clean water diversion is complete and stabilised. Section 2- Continued construction using SRP-TSF305 and sections of silt fence or DEBs to control dirty water runoff. Section 3 - The section of temporary clean water diversion located below Section 3 will be removed. During the construction of Section 3 runoff will be allowed to flow into the impoundment area of TSF3 until the permanent diversion drain is constructed and stabilised. As the permanent diversion drain is constructed it will be progressively stabilised. Shear key construction and establishment of remaining perimeter infrastructure for RF 155 embankment to continue. Dirty water directed to SRPTSF3-06 as required. KEY Erosion and Sediment Control Clean Water Diversion Dirty Water Diversion Culvert Silt Fence Sediment Retention Pond Placement of PAF in areas where runoff reports to Collection Ponds. SRP-TSF3-05 Catchment area: 3.0ha Total volume: 900m3 Dead storage: 270m3 Live storage: 730m3 SRP-TSF3-06 Catchment area: 5.0ha Total volume: 1,500m3 Dead storage: 450m3 Live storage: 1,050m3 Continued shear key construction and establish remaining perimeter infrastructure for RL 155 embankment. Section 1 - Permanent clean water diversion drain constructed and stabilised. SRP-TSF3-09 Catchment area: 1ha Total volume: 200m3 Dead storage: 60m3 Live storage: 140m3 Section 2 - Construction of permanent uphill diversion will largely need to be undertaken as a cut and cover operation due to steep topography through bush. Sections of silt fence or DEBs will be used where practicable. Minor realignment of existing clean water diversion and decommissioning of SRP-TSF303 to allow for continued shear key construction. Once the SRP is decommissioned the final section of the southern uphill diversion drain will be completed and stabilised. SRP-TSF3-08 Catchment area: 1ha Total volume: 200m3 Dead storage: 60m3 Live storage: 140m3 Section 2 Section 3 Section 3 - Construction of permanent uphill diversion. The previously construction temporary clean water diversion will be removed from below Section 3 and runoff during the construction of this section will flow downslope into the TSF3 impoundment area. This section is through the bush area and the steep topography would restrict the construction of ESCs.

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