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1.0 EXECUTIVE SUMMARY <br /> The Sunnyside Mine is located approximately 8 miles north of Silverton in northernmost San <br /> Juan County, Colorado. Slightly acidic water containing mobilized heavy metals flows out of <br /> both access tunnels to the mine. The purpose of this report is to present a conceptual hydrologic <br /> model of the mine vicinity so that the San Juan County Mining Venture (SJCMV) may be able <br /> to devise a long term plan which will allow a return to an approximation of pre-mine hydrologic <br /> conditions. <br /> Ground water in the bedrock flow system in the vicinity of the Sunnyside Mine is transmitted <br /> via fracture permeability. The pre-mining static water level in the bedrock flow system beneath <br /> Sunnyside Basin is estimated to have been at an elevation of approximately 11,500 feet above <br /> mean sea level based on the water level in the Sunnyside Mine after almost 20 years of <br /> inactivity. The majority of flow in the deep ground-water system moved southwest from the <br /> Sunnyside Basin to discharge within the Cement Creek watershed. This ground water passed <br /> through fractures in rocks containing large quantities of metal sulfides-both along highly <br /> mineralized fractures and disseminated throughout the rock. The dissolved metals content of the <br /> ground water generally increased downgradient within the ground-water flow system. In the <br /> vicinity of Cement Creek springs derived from ground water which had traversed the deep flow <br /> system are estimated to have had a pH of less than 5.0 and elevated concentrations of lead, zinc, <br /> cadmium, manganese and iron. The chemistry of the base flows of area creeks would have been <br /> similar to the chemistry of the springs supplying that base flow. The average flows of area <br /> sanjuan\stymy\110361\oet9l.Rpt 1 <br /> es� simon MEIN'0o =IEPRO' H <br />