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• i Rito Seco (south of the West pit). Water emanating from the seeps also had elevated quantities of TDS, sulphate and manganese so BMRI constructed a system to collect the seep Flow and pump the water back to the West pit. On April 8, 1999, BMRI submitted technical revision 26, as required by the Mined Land Reclamation Board, which proposed specific actions by BMRI to protect groundwater and surface water quality. In order to protect surface water quality, BMRI proposed to lower the West pit water level to a msl of 8580 feet (the elevation of the Rito Seco neaz the seeps) and maintain the .eater level at this elevation until the water quality in the West pit is able to meet applicable waver quality standazds. Theoretically, this activity should shut the seeps off which, if successfitl, would protect water quality in the Rito Seco. As reported by BMRI on February 4, 2000. the water level in the West pit is at an elevation of 8584 feet msl and the seeps have stopped flov+ing. The DMG confirmed BMRI's observation that the seeps have stopped flowing during an inspection of the site on February 11, 2000. In addition, in order to improve water quality in the West pit and the alluvial aquifer, BMRI proposed, and has initiated, a water treatment program involving anano-filtration system with an evaporation system as a backup. Water quality in the West pit has improved significantly since BMRI received a temporary discharge permit (from CDPHE) to dischazge proces:;ed water into the Rito Seco. In January, 1999 the arithmetic average of manganese, sulphate an~i TDS was 6.27 mg/l, 8I8 mg/1 and 1346 mg/l respectively (for 5 backfill wells in the West pit). ht October, 1999 the average was 3.93 mg(1, 680 mgll and 1000 mg/l respectively for the 5 wells. This is a 37% reduction in manganese, 17% reduction in sulphate and a 26% reduction in TDS in a ]0 month period. In order to prevent further degradation of the alluvial aquifer, BMRI has proposed to drill two curtain wells to capture the contamination plume in the Rito Seco alluvium. The water will be pumped back to the West pit for processing and discharged into the Rito Seco or teinjected back into the West pit (to help flush the backfill material). If these wells are successful, the plume will not continue its westwazd migration which should eliminate the risk of any potential impacts to downgradient groundwater users (the town of San Luis). The DMG also required BMRI to drill one additional point of compliance west of the zone of contamination, at which compliance with the permit conditions applicable to the quality of groundwater in the alluvial aquifer must be demonstrated. As of the date of this correspondence, [here have been no offsite w;tter quality impacts to surface water or groundwater. With continued implementation of the approved mitigation plan, we expect that no offsite impacts will occur. If you have any questions, please contact James Dillie.