EGL Ref: 9018 22 June 2022 Page 5 WAI-985-000-REP-LC-0006_Rev0.docx This report shall only be read in its entirety. • Record of construction and rehabilitation works • Record of material movements in and out of stockpiles • Visual inspection of the stockpiles • Monitoring of acid generation and lime addition on the top of the stockpiles • Monitoring of all aspects of water quality in and around the facilities: groundwater wells, subsurface and leachate drainage, collection and silt ponds Resource consents for the Tailings Storage Facilities (TSF) Storage 1A and Storage 2 and associated stockpiles require the preparation, review and update of a Tailings Storage Facility Monitoring Plan (TSFMP) (Ref. 4). Updates of the Plan are provided to Waikato Regional Council (WRC). The TSFMP includes annual review of risks, structural integrity, geochemistry, underdrainage, and groundwater. These reports are further peer reviewed by a peer review panel (PRP). 2.6. Performance to date The zoned design of the stockpiles, liming, collection of seepage with leachate and subsoil drainage, and progressive rehabilitation of surfaces has contributed to the good performance of the stockpiles and TSF embankments as designed and within the existing resource consent conditions. The monitoring results from the annual reviews indicate leachate from the stockpiles and TSF embankments is primarily collected and captured on top of the Zone A pad. Residual seepage through the Zone A liner is intercepted in the subsoil drains beneath the Zone A liner, which are positioned to intercept the ground water seepage beneath the stockpiles. A series of detection and compliance groundwater wells around the perimeter of the existing Development Site indicate that these subsoil drains are effective in capturing any seepage through the Zone A liner from the stockpiles. Similar design intent along with the annual monitoring and surveillance program is to be applied to the proposed NRS to effectively manage its performance and adherence to resource consent conditions. 3.0 DESCRIPTION OF WAIHI NORTH PROJECT AND NORTHERN ROCK STACK 3.1. Waihi North Project The WNP adds the Wharekirauponga Underground (WUG) Mine, 10km north of Waihi township, and Gladstone Open Pit (GOP) Mine, adjacent to the Processing Plant, to the existing mining operation at Waihi. This requires new tailings storage facilities to accommodate the increased tailings production. The new tailings storage is to be provided by a new TSF (Storage 3) and utilising the void created by mining the GOP. Storage 3 TSF is a zoned downstream embankment dam with a lined impoundment and is located immediately east of Storage 1A. It partially overlies the East Stockpile. The downstream embankment and lined impoundment is to be constructed using the overburden material from the GOP. The zoned embankment construction requires the GOP overburden materials to be blended and conditioned to meet the specification for the zoned embankment. Stockpiles are required for this purpose. The Storage 3 embankment is to be similar to the Storage 1A and Storage 2 embankments.
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