2008-03-31_REPORT - M1988112 - Laserfiche WebLink

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San Luis Project CDMG Annual Report March 23, 2008 Page 4 The tailing embankment piezometers were inspected monthly. Each of these installations either remained dry or contained less than 12 inches of accumulated water within the piezometer casing. Results of these inspections were reported to the Division in the monthly reports. The collection pond leak detection system was evacuated monthly and quarterly sampled and analyzed in accordance with the applicable technical revision monitoring plan. Laboratory analytical reports were submitted to the Division upon receipt from the Laboratory. The 2007 collection pond leak detection system return flow rates ranged from 16.06 to 31.48 GPAD with a mean annual collection pond return flow rate of 21.47 GPAD. Water treatment plant sludge removal was conducted twice during the 2007 calendar year. Approximately 386 tons of sludge material was transported from the water treatment plant to the tailing facility during 2007. This material was extracted from the water treatment plant ponds and transported to the tailing disposal facility for final placement. The November 2007 monthly report summarizes the 2007 sludge management activities. Technical Revisions BMRI continued implementation of TR-26 as approved on May 23, 2000. BMRI has been actively managing the West Pit and Rito Seco alluvial hydrologic systems since July 1999, and the water management plan developed in TR-26 has been fully implemented accordingly. The water management techniques employed since the submission of TR-26 to the Division has reversed and maintained the West Pit hydrologic gradient at a ground water elevation (8582 ft amsl) below the Rito Seco streambed channel since February 8, 2000 eliminating any surface water expressions. Ground water recovery wells M-32 and M-33 installed during calendar year 2000 to capture and remove contaminates contained in the Rito Seco alluvial ground water system continued to be operated throughout calendar year 2007. Ground water recovered from theses wells was pumped back to the West Pit water treatment plant, treated and discharged in accordance with the Colorado Department of Public Health and Environment discharge permit. Ground water elevations in the vicinity of these wells were maintained below an elevation of 8540 ft amsl to ensure ground water capture and prevent downgradient migration of any contaminates contained in the Rito Seco alluvial ground water system. Each of these actions has substantially improved the West Pit and Rito Seco alluvial ground water quality. A total of 107,488,200 gallons (329.89 acre-feet) of ground water was extracted from the West Pit and 7,194,500 gallons (22.08 acre-feet) of Rito Seco alluvial ground water was extracted and delivered to the water treatment plant during calendar year 2007. Of this water, 99,444,100 gallons (305.24 acre-feet) of water was treated and delivered to Rito Seco Creek in accordance with the Colorado Department of Public Health and Environment discharge permit and TR-26. A total of 8,611,200 gallons (26.42 acre-feet) of water treatment plant reject concentrate water was transferred to the tailing facility from the water treatment plant during calendar year 2007. This water was applied within the lined tailing facility to irrigate revegetation in accordance with TR- 30.