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Land Use <br />• <br />It was anticipated by CEC that from as early as the third year after seeding, managed <br />livestock grazing would be beneficial towards meeting the DMG revegetation success <br />standards. Technical Revision TR-29 (approved on August 24, 1994) allows for the <br />grazing of livestock within fenced areas to keep livestock away from the unreclaimed <br />areas. <br />Surface Water Runoff Calculations and Sediment Pond Sizing <br />In 1994, Industrial Compliance (now Terranext) completed an initial drainage study for <br />the CEC site, in which the site hydrology was updated (refer to "Technical Revision <br />Drainage Control Plan II," dated June, 1994). Later on, a design re-evaluation of the <br />existing Sediment Pond 2 and the subsequent enlargement of that facility to accommodate <br />a 10-year, 24-hour design storm event was made by Terranext, as directed by the DMG <br />(refer to Appendix A in "Technical Revision Drainage Control Plan II," dated November, <br />1994). <br />During a prolonged period of observed significant rainfall nmofl`'accumulations and the <br />overall general heavy precipitation amounts measured on site by CEC personnel during <br />early to mid 1995, the Sediment Pond 2 facility did not experience any flows through the <br />spillway section and provided for the total storage of all accumulated storm water runoff <br />• originating above and routed to this pond site. (In fact, there has been no reported <br />spillway flow from the pond facility since its original construction, circa 1980.) The <br />1995 precipitation period is discussed in detail in the 1996 Annual Hydrology Report. <br />CEC will implement a dewatering scheme for Sediment Pond 2 in 1997. Coors personnel <br />will pump excess runoff water accumulated in this pond back to the Dugout Pond, which <br />is located about 700 feet slightly upgradient and to the south-southeast on CEC property. <br />The Dugout Pond is designated as an on-site permanent impoundment and has an available <br />storage capacity that exceeds the total contributing runoffvolume associated with a 100- <br />year, 24-hour design storm (refer to "Technical Revision Drainage Control Plan II," dated <br />January, 1995). A bank of pumps (maximum combined sustained pumping rate of 1200 <br />gallons per minute (gpm)) will be used to evacuate the accumulated runoff water in <br />Sediment Pond 2 back to the Dugout Pond within a maximum time frame of 72 hours, <br />thus meeting a reasonable evacuation time period for the Sediment Pond 2 dewatering. <br />Also, in this manner, Coors can maintain a continued lowered pond level in Sediment <br />Pond 2 during prolonged periods of excess rainfall and runoff on site such as was <br />experienced during 1995. <br />Since the sediment level in Sediment Pond 2 has been virtually non-existent to very little <br />after eleven years of use, and since this pond facility has never had any measurable water <br />stored in it for more than a 24-hour period, except during the unusual prolonged period of <br />excess precipitation events in 1995, and during which time period there was never any <br />. observed spillway discharge, all previously existing man-made temporary pond sites have <br />105 5/96 <br />