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• For the year, 8.7 inches of runoff (almost entirely spoil discharge) was measured below <br />the 004 pond. The USGS ly si meter studies determined that from two to six inches of <br />recharge fluxed through the spoil, depending on snowpack. Verbal communication with <br />members of the USCS has also disclosed the fact that measurable upward leakance of ground <br />water from the Wadge underburden is recharging the spoil aquifer in addition to snowmelt <br />and rainfall. The 8.7 inches of runoff does indeed suggest there is Wadge underburden <br />discharge contributing to the Seneca II spoil recharge. During the period of June through <br />September, 1984, 3.1 inches of spoil discharge was measured. This wet year spoil <br />discharge value was used to calculate the potential maximum Seneca II-W spoil runoff <br />volume to the Dry Creek Basin. Because the clay content was higher at Seneca II-W, the <br />3.1 inches was multiplied by the ratio 25/29 to account for infiltration differences in <br />spoil with a higher percentage of fines. The resultant value, 2.67 (.223) inches was used <br />to calculate the volume of spoil runoff from both the north and central mining pits. <br />Table 17-16 presents the values used and calculated for Seneca II-W pit areas and volumes <br />of spoil discharge in acre feet and cubic feet per second for the June through September <br />irrigation season. <br />Potential Impact of Replaced Spoil on Cround Water Quality. The following impact analyses <br />includes an assessment of Seneca II-W spoil water discharge on the overburden aquifer, the <br />Wadge Coal aquifer, the Dry Creek alluvial aquifer, and the Sage Creek alluvial aquifer. <br />The following equations presented by Ferreira (1984) were utilized to calculate percent <br />increases in TDS and chemical load in tons/day. <br />L=0xCx 0.0027 <br />where: <br />L = the chemical load in tans/day <br />0 = ground or surface water flow in cfs <br />C = the TDS concentration in mg/1 <br />and <br />DSC = DSL <br />OxF <br />where: <br />DSC = resultant dissolved solids concentration in mg/1 <br />DSL = the sum of the dissolved solid load for the contaminant source and the <br />receiving source expressed as tons/day and calculated by the equation L = 0 x C <br />. x 0.0027 <br />39 <br />