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• Probable Hydrologic Consequences <br />According to data supplied by the USGS, the annual seven day minimum flow for <br />the North Fork of the Gunnison River is 25 cfs. This low flow value occurred February 17, <br />1978, is for the period of record from 1934 through 1995 and is measured upstream of the <br />Town of Somerset, CO. <br />The maximum mine water discharge during the year was 28.6 gpm. In order to <br />account for additional outcrop flow from the flooded mine, it will be assumed the mine <br />water flow equals 50 gpm. The maximum measured TDS value for the mine water during <br />the year was 3370 mg/I. <br />The PHC section of the permit projects the total flow through the alluvium is 136 <br />gpm. Of that total flow, approximately 41 gpm is subject to contamination from the coal <br />stockpile area. The quality of the contaminated water should be similarto the water quality <br />in well AA-1. For the period of 1987 though 1996, the maximum TDS measured in AA-1 <br />was 2890 in 1995. <br />The maximum TDS measurement at the upstream North Fork ofthe Gunnison River <br />monitoring station during 2000 was 90 mg/I in December. The following table presents the <br />estimated affect the mine discharge and alluvial flow will have on the quality of water in the <br />North Fork of the Gunnison River: <br />u <br />• <br />PHC North Fork of the Gunnsion River <br /> Flow m Flow cfs TDS <br />North Fork 11,220 25 90 <br />Mine Dischar a 50 0.11 3370 <br />Alluvial Flow 41 0.09 2890 <br /> <br />Combined Flow 11,311 25.20 115 <br />-g- <br />