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production year. Since full tonnage evaporation cannot take place at the same time that the lake is at full size, a highest consumptive use scenario is based on the lake being at full size while the opera- lion is winding down in the second year, therefore, a discount of 50% is applied to the evaporation losses associated with the gravel mined. This results in 50%o of 3.08 acre-feet or 1.54 acre-feet ner year. This use will only occur for the two years of mining. 3) Evaporation will occur as a result of pumping water into the pond southwest of the operation and exposing this water to the surface. Since the pond is normally wet, the increase in area of exposed water is used to determine this consumptive use. Most of the water will seep back into the ground, however, the surface area of the pond will increase by approximately 1.0 acres. Using the rate cal- culated above of 4.58 acre-feet per acre, this results in a use of 4.58 acre-feetper vear. 4) Consumptive use for dust control will be minor since the access road will be primarily main- rained with magnesium chloride. Under very dry conditions and high truck traffic, water may be used. This use is estimated at 0.7 acre-feet~er veaz. for the two years that mining will occur. A summary of consumptive uses is given below: Use T Basis Acre-feet r Lake Evaporation Evap records + precip. data 34.8 Gravel Excavation Evaporation Evap records, tonnage mined 1.54 Wetland Evaporation Evap records, area exposed 4.58 Dus[ Control -Roads Tonnage and road use 0.7 Totals 41.62 The numbers above are for worst case consumptive use since the lake is calculated at maximum surface area and it is assumed that the full mining operation will be taking place at the same time. Once the operation is terminated, the only use will be lake evaporation, which will be 3A.8 acre-feet per year. 19 Road Pit 10!02 13