2024-05-17_REVISION - M1977493 (4)

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design capacity of 10,000 gpm. Impacted water sources continue to be routed through the SDP to receive first-stage treatment. The tailing slurry and SDP effluent discharge into the Tenmile TSF water pool thereby completing the Tenmile TSF Deposition process water circuit. When tailing is being deposited on Mayflower TSF, the mill water reclaim system will continue to operate generally as described for Tenmile TSF Deposition with the addition of the Mayflower Pump Barge (Mill Barge). This barge is located in the Mayflower TSF water pool and delivers water to the North Portal of the Tenmile Tunnel. The first priority water that is delivered to the mill is the impacted water and tributary inflows delivered to the SDP and Tenmile TSF. Supernatant from Mayflower TSF will be delivered to Robinson Lake at times when the upstream sources are inadequate to satisfy the mill water demand orwhen there is storage space available in Robinson Lake. When the natural inflow to Robinson Lake is not sufficient to meet the mill water demands, the Tenmile Tunnel bulkhead valves will be opened to convey decanted water from Tenmile TSF into Robinson Lake. When the excess water in Tenmile TSF is not required at the mill or to refill Robinson Lake, the bulkhead valves will be closed to direct flows to the North Portal of the tunnel and on to Mayflower TSF where it is either stored or treated and discharged from the property through the PDWTP. G-2.6 Makeup Water Systems At certain times of the year, primarily during the fall and winter, precipitation runoff within the process water area and SDP effluent may not be sufficient to offset consumptive uses,such as evaporation and tailing water retention. During these times, process water can be released from storage in Tenmile TSF, Mayflower TSF, and Robinson Lake. The capacity for water storage on Tenmile TSF varies but generally ranges from about 500 to 2,000 acre-feet. Robinson Lake provides approximately 1,700 acre-feet of operational storage. The capacity for operational water storage on Mayflower TSF also varies but generally ranges from about 1,000 to 2,000 acre-feet. This storage water would be delivered to Robinson Lake using the Mayflower Pump Barge (Mill Barge). The drainage basin tributary to Robinson Lake is relatively small and it is therefore necessary to divert water into the lake from the Tenmile Tunnel. If necessary,freshwater can also be diverted into the North Portal of the Tenmile Tunnel using Supply Canal No. 2. This canal system diverts clean water from the Kokomo and Searle Gulch drainages. All waters entering Robinson Lake will have received first-stage treatment or be fresh water diversions via Supply Canal No. 2. Water from Kokomo and Searle Gulches can also be delivered directly into the Mayflower TSF water pool. Climax acquired an ownership interest in the Columbine Ditch water right,which is located in the headwaters of the East Fork of the Eagle River. The intent is to eventually divert this water, if needed, into the process water system as needed for makeup water. The diversion would require the installation of a pipeline from the ditch to Chalk Mountain Reservoir or Robinson Lake. G-2.7 Impacted Water Sources Waters at the site that have come into contact with mining materials, including the open pit and underground mine rubble, overburden storage facilities (OSFs), and TSFs are generally assumed to be impacted and therefore require treatment prior to discharge from the site. The impacts generally include low pH and elevated concentrations of heavy metals. The following is a list of the primary impacted water sources at the site. The general location of these sources is identified on Figure G-01. ■ Underground Mine Drainage and Pit Runoff ■ Storke Area Seepage ■ Camp Area Runoff and Seepage ■ North 40 OSF Runoff and Seepage ■ McNulty OSF Runoff and Seepage ■ Robinson Dam Seepage Exhibit G G-5 May 2024