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RESPONSE <br />• <br />n <br />U <br />• <br />Modeling of geologic conditions has been utilized to predict subsidence potential; the results of the modeling are <br />set forth in Exhibit 7, Subsidence Predictions. Overburden stratigraphy, uniaxial compressive strength and tensile <br />strength, angle of draw, caving, and flexure characteristics have been modeled using methods described in the <br />Subsidence Engineer's Handbook (NCB Mining Department, 1975). <br />Modeling of surface water conditions has been utilized as set forth in Exhibit 8, Sediment Control Plan. <br />Characteristics of surface runoff, peak flow, reservo'v routing, sediment yield, and theoretical detention time have <br />been modeled using the techniques <br />described in "Procedures for Determining Peak Flows in Colorado" (USDA, SCS 1977) and "Applied Hydrology <br />and Sedimentology For Disturbed Areas" (Barfield, Wamer and Haan 1981). These techniques have been <br />incorporated into the DEPOSITS model, which has been utilized in the design of treatment facilities for the <br />underground mine. Finally, streamflow and water quality in streams draining the general area has been modeled using <br />the WATBAL model, for the purposes of the assessment of probable hydrologic consequences of mining on surface <br />water, required by Rule 2.05.6(3). <br />Modeling of ground water conditions has been utilized in this application, specifically under Rule 2.05.6(3) and in <br />Exhibit 9, Aquifer Test Data. Dewatering, drawdown and solute transport characteristics have been modeled using the <br />analytical methods described in "Ground Water Hydraulics" (Lohman 1979), "Selected Handheld Calculator Codes <br />for the Evaluation of the Cumulative Hydrologic Impacts of Mining" (USDI. <br />Permit Renewal No. 3 <br />2.oa-11.1 ~yg+~q©;-~~a pPR 2 4 2~9G <br />11/1/99 <br />