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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 <br />17, 1978, is for the period of record from 1934 through 1995 and is measured upstream <br />of the Town of Somerset, CO. <br />The maximum mine water discharge during the year was 34.6 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 <br />during the year was 3570 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 similar to the water <br />quality in well AA-1. For the period of 1987 though 1996, the maximum TDS measured <br />in AA-1 was 2890 in 1995. <br />The maximum TDS measurement at the upstream North Fork of the Gunnison <br />River monitoring station during 1999 was 120 mg/I in December. The following table <br />presents the estimated affect the mine discharge and alluvial flow will have on the <br />quality of water in the North Fork of the Gunnison River: <br />PHC North Fork of the Gunnsion River <br /> Flow m Flow cfs TDS <br />North Fork 11,220 25 120 <br />Mine Dischar a 50 0.11 3570' <br />Alluvial Flow 41 0.09 2890 <br /> <br />Combined Flow 11,311 25.20 145'. <br />-I1- <br />