2024-05-17_REVISION - M1977493 (4)

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G-3.3.4 Figure G-08: Robinson and Tenmile TSF Area A. Robinson TSF It is assumed that the surface runoff from Robinson Tailing Storage Facility(TSF)will eventually be clean and discharge into the ESC. Most of Robinson TSF has been capped and reclaimed. The existing pool area(approx.60 acres)will be regraded and covered appropriately. The surface would be sloped to drain east to the ESC to achieve a dry cover configuration. B. Water Conveyance The ESC and ESP would continue along Robinson and Tenmile TSF's to convey clean and impacted water sources down the Tenmile Creek valley. It is assumed that the existing East and West Interceptors would continue to operate at closure. Eventually the East Interceptor could be decommissioned with east side clean water reporting to the ESC. The existing TDL would be used to convey impacted water to the SSDP until the SDP is decommissioned. At that time all impacted water above 3 Dam would be conveyed is the ESP. C. Sludge Densification Plant The SDP would eventually be decommissioned and demolished. At that time all water treatment would occur at the PDWTP. The Lime Station would also be demolished. A sludge conveyance pipeline is shown on Figure G-06 to transport the SDP sludge to the sludge cells on Mayflower TSF. This pipeline is not needed when the SDP is decommissioned. D. Tenmile TSF The surface of Tenmile TSF (approx. 550 acres) will be capped and reclaimed to a dry cover configuration. The existing surface grade drains to the Tenmile Riser. It is assumed that the surface runoff from Tenmile TSF will eventually be clean and discharge into the Tenmile Tunnel Extension (north). It is not currently feasible to make the TSF drain to the east to the ESC. The tunnel north portal is too low to discharge into the West Interceptor. Therefore, Figure G-08 shows a new pipeline/channel across 3 Dam to convey the clean runoff to the ESC. This system would also intercept clean surface water runoff from the downstream face of 3 Dam. A surface flood spillway will be required that would discharge to the east side of the valley into the ESC. A conceptual location of a spillway channel is shown on Figure G-08. It is assumed that the SDP sludge cell will eventually be capped and reclaimed. Sludge from the SDP would need to be conveyed to the Mayflower sludge cells by pipeline or truck until the SDP is decommissioned. E. 3 Dam The majority of 3 Dam has been capped and reclaimed. There are approximately 40 acres that remain to be capped and reclaimed. G-3.3.5 Figure G-09: Mayflower TSF Area A. Mayflower TSF The surface of Mayflower TSF(approx. 570 acres)will be capped and reclaimed. It is assumed that the surface runoff from the north portion of Mayflower TSF will eventually be clean. A collection channel across the TSF beach is required to convey this clean water to the ESC. The final surface contours shown on Figure G-09 are based on an ultimate dam crest elevation of 10,820 feet. An impacted water pool (shown with a surface area of 133 acres) would be required in the back of Mayflower TSF. This is needed to provide detention storage for impacted water and attenuate flows to the PDWTP. Impacted water from the pool would be conveyed to the PDWTP. This could initially be done using the existing barge pump system. Eventually a new fixed pump station would be constructed. Both Exhibit G G-13 May 2024