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SURFACE WATER HYDROLOGY The CEC site drainage plan and facilities are presented in Appendix K of the Permit, and can also be found in the, "Teclmical Revision, Drainage Control Plan II," submitted in June, 1994. Existing diversioi>/drainage ditches that Dave been constructed along the access roads and around the north and east sides of the CEC property presently serve to convey surface water runoff to Sediment Pond 2. The existing drainage facilities, as well as existing site topographic features, are shown on the Existing Surface Features Map. It is noteworthy that total long-term sediment accumulation in Sediment Pond 2 has not been a problem in twelve years of use. The Dugout Pond is to remain undisturbed at site closure in order to provide a continued wildlife habitat, in accordance with CDMG direction. The permanent drainage facilities for final site reclamation are shown on the Reclamation Contour Map and Drainage Plan drawing. All standing water accumulation in the former mining pits, except for the surface water runoff which soon evaporates or infiltrates into the substuface, has been eliminated, and the pit sumps have been backfilled. Due to the deep eolian sand deposits over the mine site acid the sand's Itiglt infiltration characteristics at this site, • significant amounts of moisture are lost to the deep percolation of rainfall during major storm events. CEC began implementation of a dewatering scheme for Sediment Pond 2 in 1997, in accordance with its newly revised (June, 1997) "Spill Prevention, Control and Countermeasures Plan" for the site. Wlten appropriate, CEC personnel will pump excess runoff water accumulated in this pond back to the Dugout Pond, which is located about 700 feet slightly upb~adient and to the south-southeast on CEC property. The Dugout Pond is designated as att on-site permanent impoundment and ltas an available storage capacity that exceeds the total contributing runoff volume associated with a 100-year, 24-hour design stone (refer to "Technical Revision Drainage Control Plan II," dated January, 1995). A batilc of pumps (maximum combined sustained pumping rate of 1200 gallons per minute (gpm)) will be used as needed to evacuate the accumulated nmoffwater in Sediment Pond 2 back to the Dugout Pond within a maximum time frame of 72 hours, thus meeting a reasonable evacuation time period for the Sediment Pond 2 dewatering. Also, in this manner, Coors can maintain a continued lowered pond level in Sediment Pond 2 during prolonged periods of excess rainfall and runoff at the site, similar to that which was experienced during the Spring of 1995. AHR-1997 - 81-