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Under PR06-06, only limited main and sub-main development will occur. Given the limited azea that will be <br />developed, groundwater inflows are expected to be minimal. Prior to actual mining of this azea, inflow <br />modeling will be completed and incorporated into the PAP. <br />• (21 The use of anproved modeling. techniques maybe included as Hart of the permit application, but <br />the same surface and Around water information may be required for each site as when models aze not used. <br />RESPONSE <br />Modeling of geologic conditions has been utilized to predict subsidence potential; the results of the <br />modeling aze set forth in Exhibit 7, Subsidence Predictions. Overburden stratigraphy, uriiaxial <br />compressive strength and tensile strength, angle of draw, caving, and flexure characteristics haye been <br />modeled using methods described in the Subsidence Engineer's Handbook (NCB Mining Department, <br />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, reservoir routing, sediment yield, and theoretical detention <br />time have been modeled using the techniques described in "Procedures for Detemrining Peak Flows in <br />Colorado" (USDA, SCS 1977) and "Applied Hydrology and Sedimentology For Disturbed Areas" <br />(Barfield, Warner and Haan 1981). These techniques have been incorporated into the DEPOSITS model, <br />which has been utilized in the design of treatment facilities for the underground mine. Finally, streamflow <br />and water quality in streams draining the general area has been modeled using the WATBAL model, for <br />the purposes of the assessment of probable hydro]ogic consequences of mining on surface water, required <br />by Rule 2.05.6(3). Modeling of ground water conditions has been utilized in this application, specifically <br />under Rule 2.05.6(3) and in Exhibit 9, Aquifer Test Data. Dewatering, drawdown and solute transport <br />characteristics have been modeled using the analytical methods described in "Ground Water Hydraulics" <br />(Lohman 1979), "Selected Handheld Calculator Codes for the Evaluation of the Cumulative Hydrologic <br />• Impacts of Mining" USDI. <br /> <br />PR06-07 2.04-11.1 11/07/06 <br />