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• <br />EXHIBIT A <br />Calculation Sheet <br />Effects of Mine Discharges on the Water Ouality of the Alluvium <br />Foidel, Middle and Trout Creek Confluence Area <br />Methodology <br />Estimate water quality of surface water recharging alluvium during a <br />normal and a dry year. Estimate the natural water quality of the <br />alluvium. Based upon the amount of recharge in each year, use a mass <br />balance methodology to estimate the resultant water quality in the <br />alluvium. <br />Average Dissolved Solids Concentration in Alluvium: <br />Use alluvial well 08-AV-2 completed in the Foidel Creek Alluvium <br />Average dissolved solids concentration is 1016 mall (Table A-1) <br />• Amount of Recharge: <br />Saturated thickness of alluvium at beginning of Spring recharge period: <br />7 feet (CYCC No. 3 Mine Permit, Cross-section of Foidel Creek alluvial <br />valley) <br />Water rise during low flow spring runoff: 1 feet in March, 1981 <br />(Figure A-1) <br />Max. water rise during runoff: 5 feet in April, May and June, 1984 <br />(Figure A-1) <br />• <br />Stream Flow During Normal and Low Flow Recharge Months (Stn 3700) <br />March 1985 flaw: 5.14 cfs (USGS stream flow records) <br />March 1981 flow: 1.46 cfs (USGS stream flow records) <br />Ratio: 5.14:1.46 = 3.5:1 <br />April, May, June 1985 mean flow: (36.3 + 55.9 + 8.8)/3 = 33.7 cfs (USGS <br />stream flow records) <br />23 <br />Revised 10/1/86 <br />