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a� <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />303 866 -3567 <br />FAX: 303 832 -8106 <br />March 29, 1991 <br />Mr. Larry Perino <br />P. 0. Box 177 <br />Silverton, CO 81433 <br />4-c f S C2 <br />111 IIIIIIIIIIIIIiii <br />STATE OF COLORAUU <br />Roy Romer, <br />Governor <br />Fred R. Banta, <br />Division Director <br />RE: Technical Revision No. 11, San Juan County Mining Venture, Sunnyside Mine, <br />File No. M--77 --378, <br />Dear Mr. Perino: <br />As we discussed, the Division has reviewed the proposal to modify the <br />reclamation plan for Tailings Pond No. as submitted on February 20, 1991 as <br />Technical Revision No. 11. In order to consider approval of the revision, <br />your commitment to the following conditions is requested: <br />1. An approximate depth of 12 inches for placement of a cover of <br />borrow material is proposed. The Division considers 12 inches to <br />be the minimum acceptable and an average of 18 -inch thickness to be <br />more appropriate for the intended use as a barrier to ground water <br />percolation and plant growth medium. <br />2. The reduction in water entering the pile as runoff from upslope is <br />important to protect the Animas River from possible acidic leachate <br />discharge from the pile. The Division recommends an impermeable <br />liner be constructed in a ditch located to divert upslope runoff <br />away from the pile. The design of a diversion with an impermeable <br />liner, or other method, should be submitted for Division review <br />within 30 days. <br />3. The top of the pile is proposed to be graded at a 2 percent slope <br />toward the hillside. This will function to drain the runoff off <br />the pile, but may encourage channelized flow where the pile joins <br />the natural hillside. The design of a non - erosive channel or <br />channel treatment should be submitted for Division review within 30 <br />days. <br />