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• • • iii iiiiiiiiiiiiiiii ~/~` Cripple Creek & Victor Gold Mining Company 999 l1 ~ A Joint Venture -Pikes Peek Mining Company, Manager `~/ ~L~/ Operations Office Englewood Office PO. Box 191, 2755 State Highway 67 5251 DTC Parkway, Suite 700, Englewood Victor, Colorado 80860 Colorado 80111 (719) 689-2977 • FAX (719) 689-3254 (303) 889-0700 • FAX (303) 889-0707 July 12, 1994 SENT BY FACSIMILE -COPY FOLLOWS BY MAIL Mr. Berhan Keffelew Environmental Protection Specialist Colorado Department of Natural Resources Division of Mines and Geology Off ice of Mined Land Reclamation 1313 Sherman Street, Room 215 Denver, Colorado 80203 ~;IyR_ ~ ~~~• - /U~ I419~4 S 0p 0~ ~i'~~~E/di~ 6 `~(,coY Reference: Cresson Project: Permit Number M-80-244: Valley Leach Underdrain Configuration. Dear Mr. Keffelew: In accordance with our discussion of late this afternoon, we are submitting to you the proposed change in a segment of the underdrain configuration. This change will maintain the flow capacity of the underdrain and improve the construction technique. The revised cross section is submitted as Attachment 1 to this request. This change in configuration will only occur upgradient of the area where the total width of the underdrain is to be 20 feet or less. In the remainder of the area where the total width increases from 20 up [0 100 feet, the original configuration will remain. The original configuration is one of the entire underdrain excavated to a single grade with the pipes located in the middle of the excavation and the pipe bedding material piled around and over the pipes. Then the larger underdrain material will be placed on top of the bedding material as well as beside the bedding material and across the entire design width of the drain area (up to 100 feet). In the areas narrower than 20 feet, with the proposed change, it will be much more efficient to excavate a trench for the pipes, lay the pipes in bedding material, and then fill that trench with bedding material. Then the bench area above the trench will be filled to the design cross-section with the larger underdrain rock -which covers the beddng rock in the lower trench.