2018-08-22_REVISION - M1977493A - Laserfiche WebLink

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Technical Revision (TR-28) Climax Molybdenum Company Environmental Protection Plan Permit No. M-1977-493 Water from the Arkansas River drainage introduced to the Tenmile drainage includes water from the underground mine workings (5-Shaft) and water from the Arkansas Well used for domestic supply at the mill. Water introduced from the Eagle River drainage includes dam seepage (1 and 4 Dam), and runoff collected in Robinson Lake that may enter the Tenmile drainage area as makeup to the mill water circuit. All other waters managed by Climax originate as snow or rainfall within the Tenmile Creek drainage on the mine site or on land above the interceptor canals. The upper Tenmile Creek Watershed, including its tributary drainages of McNulty Gulch, Kokomo Gulch, Searle Gulch, Rose Gulch, Tucker Gulch, Humbug Creek, Mayflower Creek, and Clinton Creek, has been subject to extensive placer and lode mining, milling, and smelting operations since the discovery of placer gold in the 1860s (reference for historic information- Dempsey, S. and J.E. Fell, Jr. 1986; Mining the Summit. University of Oklahoma Press). At one time, the Tenmile Creek Valley within the present boundaries of Climax supported four incorporated towns: Carbonateville, Robinson, Kokomo, and Recen. At the peak of historic mining development in the 1880s, more than 10,000 people resided in the valley during the snow-free period. A number of mills and several smelters processed lead/silver, gold, copper, and (later) zinc ores extracted from the numerous mines in the area. Thus, Tenmile Creek Watershed from the top of Fremont Pass to well downstream of the Climax property line was impacted prior to the discovery and development of the Climax molybdenum ore body. Operations at Climax since the early 1970s have stabilized and dramatically improved environmental conditions in the watershed downstream of the property. Such improvements are evidenced by the documented recovery of the aquatic ecosystem in Tenmile Creek from its virtually sterile condition prior to 1970. Within the Tenmile Creek Watershed certain impacted waters are collected and routed to the SDP, for first stage metals treatment and discharged to the Tenmile TSF. The SDP was incorporated into the mine's water treatment/management system in 2007 (AM-05) to improve both water treatment efficiency and sludge management and has a capacity of approximately 6,900 gpm. Employing lime neutralization, precipitation/settling, and sludge thickening steps, the SDP significantly reduces the water content of solids placed in the Tenmile TSF, thereby making more efficient use of the facility's solids storage capacity. The SDP produces a sludge that is deposited in a constructed cell on Tenmile TSF. Evaporation and freeze/thaw cycles increase sludge density. Water treatment, following the SDP, is accomplished using the water pool of the Tenmile TSF and the Property Discharge Water Treatment Plant (PDWTP) for first and second stage treatment, respectively. In the first stage treatment, discharges from the SDP and impacted waters that exceed the SDP's treatment capacity of 6,900 gpm are treated by lime addition and settling in the water pool of the Tenmile TSF. In the second stage, treated water is decanted from the Tenmile TSF and flows by gravity into the Mayflower TSF where it is pumped by barge to the PDWTP (TR-19). At the PDWTP pH is again adjusted upward with lime addition to further precipitate metals. The stage two treated water at the PDWTP is neutralized with sulfuric acid before being discharged at CDPS Permit Outfall 002A to merge with flow from the Interceptor System before it is discharged at CDPS Permit Outfall 001A. Prior to construction and operation of the PDWTP, stage two treatment was accomplished by diverting stage one treated water from Tenmile TSF to a lime addition facility on 3 Dam and then allowing treatment to occur in the Mayflower TSF water pool. Phase 1 tailing Deposition began at Climax with the restart of operations in 2012. In Phase I Deposition, tailing slurry is deposited in the Tenmile TSF, and excess water is reclaimed for use in the mill via the Tenmile Decant and Tenmile Tunnel. Phase I Deposition will cease when the Tenmile TSF reaches capacity as described in TR-20. Phase II Deposition began in August 2014 when Climax began delivering tailing to the Mayflower TSF-(5 Dam) through a combination of new and rehabilitated tailing delivery pipelines (TDLs). Like the Tenmile TSF, the tailing slurry is being deposited in the Mayflower TSF utilizing the upstream deposition method by operation of a header and spigot system along the crest of 5 Dam. The mill water reclaim system from Tenmile TSF will continue to operate as previously described. Phase 11 Deposition in Mayflower TSF uses the Mayflower Barge and reclaim water pipeline (TR-23). This process water barge is located in the Mayflower TSF water pool and delivers water from the pool to the north portal of the Tenmile Tunnel where it is directed to Robinson Lake. EPP: Version R4 T-25 August 2018