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RESPONSE TO DMG COMMENTS REGARDING POND G <br />• In response to comments concerning Pond G from the Department of Mining and Geology (DMG) and at <br />the request of Twentymile Coal Company (TCC), Montgomery Watson has provided [he following: <br />1.0 POND G HYDROLOGY CHECK <br />• Pond G has been evaluated as follows: <br />Pond G has been reviewed and divided into appropriate subwatersheds delineating <br />reclaimed, disturbed, and undisturbed areas. subwatersheds have been assigned <br />hydrological and sedimentological parameters. This information is provided. <br />Using pond as-built information from the Epp survey and 1999 survey information <br />provided by TCC. SEDCAD4 modeling was utilized to predict that Pond G will meet <br />water quality requirements when the l0-year, 24-hour storm event is applied to the <br />watershed. <br />Also, utilizing as-built information from the Epp survey and information provided by <br />TCC, SEDCAD4 modeling was utilized to show that the Pond G emergency spillway <br />structure can safely pass the peak flow from the 100-year. 24-hour storm event (MSHA <br />requirements). <br />Pond G was modeled with principal and emergency spillways. <br />SEDCAD4 computer printouts are provided along with Map 9A, which shows the delineated watershed. <br />• <br />• <br />