1989-11-01_REVISION - M1977378 - Laserfiche WebLink

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1111111111111111111 999 AMERICAN TUNNEL WATER TREATMENT UPGRADE TECHNICAL REVISION Introduction San Juan County Mining Venture proposes to upgrade the existing water treatment facilities of the American Tunnel Portal . All work to be performed is on previously disturbed permitted area. Current Conditions All mine water discharge is treated and subsequently discharged into four settling ponds . These four ponds allow the suspended solids to settle before the water is discharged into Cement Creek. All ponds are cleaned on a regular basis to maintain sufficient holding time for the solids to settle. Each pond has its own permitted discharge that could be used to discharge while cleaning a pond downstream. It is important to maintain the longest retention time possible by routing through as many settling ponds as possible to maintain acceptable water quality in the discharge stream. Current piping arrangements do not allow this flexibility and this routing is being done by pumps, although the pumps being used do not have the capacity to handle the complete flow. Proposed Work A new 12" dia. pipeline will be installed on grade along the south edge of the ponds . This line will enable any one of the four Ponds to be by-passed for cleaning and maintain three working ponds for adequate retention of mine water before discharge into Cement Creek. The line will be buried along its entire length and the surface smoothed to provide a roadway along the ponds . The integrity of the existing dams will not be affected , as all trenching will be carried out to the outside of the ponds . All four decants will be replaced with new 12" dia . standpipes. Existing discharge lines through the darns will remain and be utilized with the new decants; therefore the integrity of the dams will be maintained . Replacement of existing decant structures will. be spread over the next couple of years . A launderer will be installed at the inlet of Pond #1 . Water will be routed through the launderer and allowed to flow uniformly through numerous discharge points into the pond . This will spread the flow of water going into the pond, and eliminate short-circuiting. If the launderer appears to work in Pond #1 , then additional launderers may be installed in Ponds 2 , 3 and 4 .