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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 outcrop seepage discharged from the treatment pond during the year <br />vas 14.3 gpm with a maximum TDS of 3720. In order to account for additional seepage <br />not intercepted by the treatment pond, it will be assumed a total of 50 gpm is seeping from <br />the outcrop. <br />The PHC section of the permit projects the total flow through the alluvium is 136 <br />qpm. 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 quality <br />in well AA-1. For the period of 1987 though 2002, the maximum TDS_ measured in AA-1 _ _ _ <br />was 3630 in 2002. <br />The maximum TDS measurement at the upstream North Fork of the Gunnison River <br />monitoring station during 2003 was 110 mg/I in December. The following table presents <br />1:he estimated affect the mine discharge and alluvial flow will have on the quality of water <br />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 25.0 110 <br />Mine See a e 50 0.11 3720 <br />Alluvial Flow 41 0.09 3630 <br /> <br />Combined Flow 11311 25.2 139 <br />Revised 9/22/04 <br />-8- <br />