1997-08-18_HYDROLOGY - M1977493 - Laserfiche WebLink

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1111111111111111111 / 999 © CLIMAX MOLYBDENUM COMPANY COLORADO OPERATIONS A Division of Cyprus Climax Metals Co Climax Mine Hwy.91 Climax,Colorado 80249 (719)486-2150 Fax:(719)486-2251 tKugust 18, 1997 Hand Delivered Mr. Allen Sorenson Division of Minerals and Geology ✓ 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Modified design consideration fs or 4-Dam Seep Return System, Permit No. M- 0,--77-493 Dear Mr. Sorenson: This letter follows our conversation of July 15 regarding activities at the Climax Mine relative to the 4-Dam Seep Return System. In that conversation, we discussed the installation of the return line to Robinson Reservoir that was reviewed and accepted by the Division in 1996 as an appropriate modification to an existing Environmental Protection Facility. We further discussed the construction design that entailed the placement of a liner along the entire length of the ditch. As you will recall, water quality improvement in the seep water at the toe of 4-Dam and the construction constraints required to place a liner along the length of the ditch resulted in reevaluation of the design and consideration of alternatives to secondary containment along the return line. Climax Molybdenum Company (CMC) requests your acceptance of the following alternative that will serve to substitute the liner installation in the return system. The original design will remain below the dam crest. The alternative consists of two components. First, the line, once constructed and placed in the trench, will be pressure tested according to manufacturer's system testing guidelines (attached). The line will be tested prior to commissioning the line using 4- Dam seep water. Any leaks identified in the testing will be repaired. Second, a pressure drop switch will be installed at the seep return station to shut down the system in the event of catastrophic failure. Because the pump station operates intermittently, the sensor will be programmed with the pump PLC to measure pressure drop several minutes after pumping has initiated. A yet-to-be determined pressure drop will be programmed into the PLC to control pump operation. Pressure drops in excess of the programmed level will trigger the existing alarm on the crest of 4-Dam and shut down the pumps. As with the remainder of the return system, the pressure test, containment passage through 4-Dam, and the installation of the sensor will be certified in accordance with Rule 7.3.2 (2). 1 have attached water quality analyses from February and July 1997 for the seeps at the pump station. You will note that the values have dropped significantly. Because of the.