2012-03-23_REPORT - M1988112 - Laserfiche WebLink

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San Luis Project CDRMS Annual Report March 22, 2012 Page 3 Tailing facility under drain flows were monitored at the base of the embankment to determine the under drain return flow to the collection pond. The 2011 under drain flow rates ranged from 20 to 33 gpm with a mean under drain flow rate of 28.25 gpm. As specified in TR -31 and TR -32 monitoring plans, monthly and quarterly pond analysis were conducted and reported to the Division. 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 monthly reports. The tailing 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 2011 collection pond leak detection system return flow rates ranged from 20.32 to 31.48 GPAD. Water treatment plant sludge removal was conducted twice during the 2011 calendar year; approximately 90 tons of sludge were removed from the water treatment pond and placed to the drying pad containment and subsequently to the tailing facility for final placement. Technical Revisions /Permit Amendments BMRI continued implementations 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 techniques 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 groundwater elevation (8582 ft amsl) below the Rito Seco stream channel elevation since February 8, 2000 eliminating any surface water expressions. Groundwater recovery wells M -32 and M -33 installed during the 2000 calendar year to capture and remove contaminates contained in the Rito Seco alluvial groundwater system continued to be operated throughout the 2011 calendar year. Groundwater recovered from these 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 or to the Tailing Disposal Facility for water management. During the year approximately 43,373,000 gallons (133 acre feet) of water was discharge from the water treatment plant and approximately 61,275,000 gallons (188 acre feet) of water was pumped to the tailing facility for water management. Groundwater elevations