1995-08-11_REVISION - M1977493 (9)

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5.3 Ten Mile Creek Watershed 5.3.1 Potential Sources of Contamination Of the three watersheds affected by the Climax Mine operations, the greatest potential impacts involve Ten Mile Creek drainage. Understanding the history of this watershed is extremely significant to its present and future condition. The upper Ten Mile 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 places 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, Ten Mile Valley within the present boundaries of Climax supported four incorporated towns: Carbonateville, Robinson Camp, Kokomo and Recen. At the peak of historic mining development in the 1880s, more than 10,000 people resided in the valley during the snowfree 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, Ten Mile Creek watershed from the top of Fremont Pass to well downstream of the Climax property line was severely impacted prior to the discovery and development of the Climax molybdenum orebody. Indeed, 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 documentable recovery of the aquatic ecosystem in Ten Mile Creek from its virtually sterile condition prior to 1970. The historic development and present operations of the Climax Mine have placed numerous potential sources of contamination in upper Ten Mile Creek valley (Table 2). Beginning at the top of the watershed, these identified sources are: 1) process water tanks; 2) designated chemicals (stored and used) for production of concentrates; 3) process water circuit (including mill water supply lines); 4) process facility/mine yard (aka: camp) run-off; 5) haul road run- off, 6) acidic underground mine water; 7) OP dumps (waste rock) seepage; 8) E-Dump (waste rock) seepage; 9) McNulty dump (waste rock) seepage; 10) tailing delivery system; 11) designated chemicals (stored and used) for treatment of mine water; 12) Robinson tailing impoundment; 13) Ten Mile tailing impoundment; 14) Mayflower tailing impoundment; 15) historic acidic mine drainages; 16) stormwater run-on to the water management circuit; and 17) fugitive dust(tailing and potentially acid-producing non-tailing dust). With the exceptions of a catastrophic failure of the process water tanks, the process water ' circuit, the western onion of the Robinson tailing impoundment discussed in Section 5.2 and P g P ( )� 20