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-J Draw, or 2) Restrict mining nctivit.i~•r; to tho;c are:as Chat will not subntantially influence Ennis Draw. Although these proposal; arc good practice, when the application was submitted the probablr_ lrxation of the channel was not l:no:gyn. The Division therefore, required that the applicant conduct additional studies to delineate the alluvial aquifer of Gnni~s Draw. Coors responded by submittiny the results of an electrical resistivity study, which identified the possible and probable Locations of the channel (Appendix F-1). The results show that the pit will approach within ISO feet of Ennis Draw. Although the Division is fairly confident with the findings and with Coor's mitigation proposals, the Division realizes that resistivity studies arc not an exact science and that the effects on Ennis Draw from mining so close ire hand to predict. In lieu of this, the Division would like to see one monitoring well located on the extreme west edge of Ennis Draw adjacent to Pit A. This well would be much more sensitive to drawdown from the pit and mining-related chanyes in water quality than the exisiting monitoring wells located farther to tlrr_ east. The following .stipulation is therefore required: THE APPLICANT SHALL 1fONITOR THE EXISTING FIRE PROTECTION WELL ACCORDING TO THE REQUIREAfENTS LISTED IN THE MONITORING STIPULATION OF THIS D000- FfENT . The applicant has also addressed the changes in ground water quality due to the proposed mining operations. when water passes through spoil piles the potential exists for changes in the water's quality. .Studies on the Williams Fork and Fort Union formations have shown that effluent water will contain dissolved solids concentrations ranging from 1 to 2 times that of saturated overburden extracts. The applicant prepared saturated er.trac.ts from composite grab samples taken from 3 cores in the Laramin_ formation. The results displayed on page 46 of Appendix I show that the existing dissolved solids concentration is greater than that in the saturated ertracts. If the above predictions are true the quality of pit inflow should not change significantly and should therefore be sufficiently diluted where the aquifer discharges to Ennis Draw. However, since the amount of water available For dilution in Ennis Draw is not known, it would be difficult to tell what impacts would occur if the spoil water degrades more than the applicant predicts. Zf the hydraulic conductivity of the spoils is greater than the surrounding aquifers, there may be a concentration of flow through the spoils which will magnify thr_ problem. To resolve this concern the Division requires the following stipulation: WITHIN 90 DAYS OF PERMIT ISSUANCE THE APPLICANT SHALL SUB.MZT AN ACCEPTABLE PLAN TO INSTALL A SPOIL WELL IN PIT B TO IdONZTOR SPOIL [•.7lTEP. QUALITY AND QUANTITY. -- The final impact considered by the applicant was the potential for chanyes in the recharge capacity of the Z,aramie overburden. The baseline investigation of recharge capacity revealed thaC very little rechnrye t:o t:he Laramie occurs at the mine site. This can be attributed to the water holding capacity of the thick layer of overlying blow sands and the Fact that the site experiences high evapotranspiration rates and only 12 inches of precipitation per year. The post-mining condition of rechnrye is not predicted to change significantly. Although the hydraulic properties of the spoil are difficult to predict, the large clay content of the Laramie formation suggests that the hydraulic conduc- tivity of the spoils will be close to baseline conditions. The effect of