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Mined Land Reclamation Division December 29, 1981 Page 2 Experience to date at the mine indicates that inflows have totaled about 30,000 gpd. If inflows should continue at that rate, annual depletions will be about 30 af. Recognizing that a range exists between estimated inflows (70 af) and inflows estimated from pit dewatering (30 af), I believe the amount of water Coors will actually provide for replacement should be estimated on or before June 1, 1982 based upon pumping rates of pit inflows in the interim. Estimates of inflows and amounts to be exchanged through GASP in subsequent years will be provided in an annual report to the State Engineer commencing on February 1, 1983 and every February 1 thereafter. Tributary water will be intercepted by the mine workings from the overburden shales and silts tones of the Laramie Formation. All water intercepted by the pit will be pumped into lined settling ponds. A continuous measuring flow device will be installed to measure actual inflows. All water pumped into the ponds will be consumed through evaporation or removal for road dust control. Tributary water will also be lost directly to the atmosphere from the working face of the active pit. Based on our experience at the mine, the upgradient (south) wall of the pit will seep water. That 6.6-acre surface area face will experience seepage over about 25% n+ its area. Assuming that the evaporation in the Keenesburg area is about 40- inches annually, the evaporation from the pit will be about 5.5 of per year. Therefore, depletions will total a maximum of 75.5 of in 1982 and 35.5 of in years thereafter. Thus far, I have discussed net water losses to the system. However, the mining activity will also introduce non-tributary water into the South Platte Basin through irrigation of reclamation vegetation with deep well water. This water will be pumped from two non-tributary, Laramie-Fox Hills aquifer wells, Permit Numbers 24650-F and 24651-F, permitted and drilled in 1980. Our reclamation plan calls for revegetation of about 50 acres annually with native-type plants which would be irrigated during the first growing season. According to the vegetation studies conducted by Colorado State University, 9 inches of irrigation should be applied during the first growing season. Utilizing the Blaney-C riddle method and the assumptions noted on the attached table, we have determined that about 2.9 inches of the 9-inch application would be consumptively used. The 6.1-inch balance would move into soil moisture storage and eventually migrate to recharge the ground water system. I believe that the 6.1 inches per acre/year, or 25.4 of annually will act as a replacement to the tributary water depleted by the mining operation. Therefore, the gross depletions, up to 75.5 of in 1982 and 35.5 of thereafter will be offset by 25.4 of of on-site, non-tributary replacements leaving a net amount of 50.1 and 10.1 af, respectively, of depletions to be replaced from other sources.