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~~ • - • III IIIIIIIIIIIIIIII <br />' sss <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanment of Natural Resources <br />1313 Sherman St., Room 215 I`~~ <br />Denver, Colorado 80203 I <br />Phone: (3031 866-3567 <br />FA%:(3031832-8106 <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Rny Romer <br />September 6, 1994 envernnr <br />. Ken Salazar <br />Executive Dneaor <br />Mr. John E. Hardaway <br />Manager Environmental Affairs MichaelB Long <br />Division Dr.eno~ <br />Cripple Creek and Victor Gold Mining Company <br />P.O. Box 191 <br />Victor, CO 80860 <br />RE: Surface Preparation of Soil Liner (geosynthetic subgrade), Cresson <br />Project, Permit No. M-80-244 <br />Dear Mr. Hardaway: <br />Your "Report of Puncture Resistance Test Results For Geomembrane Tested <br />With Specification Soil Liner (2 inch minus)" dated September 2, 1994 <br />has been reviewed by myself and by Dr. Jim Pendleton. The test results <br />show that the 80 mil VLDPE remained intact and functional under the <br />stresses imposed in the test apparatus. The Division concurs that the <br />test adequately simulates conditions that will exist at the Cresson <br />leach pad installation. As was indicated in the Division's 8/29/94 <br />inspection report, these favorable test results allow the Division to <br />approve up to 2 inch rocks in the exposed surface of the geosynthetic <br />liner subgrade. Such approval is granted by this letter. <br />The following conditions apply to this approval: <br />1. The Division is concerned, as was enumerated in our on-site <br />meeting 8/29/94, that rocks at the exposed surface of the <br />geosynthetic subgrade will break up under high vertical stresses <br />imposed when the heap is loaded. Breakage of this type occurred <br />in the test cell. Rocks at the surface of the exposed <br />geosynthetic subgrade must be adequately embedded in the soil <br />liner fill to minimize the potential for the development of <br />differential stresses on the rock particles that could result in <br />breakage and/or rotation. Rocks at the exposed surface with <br />adjacent visible void space must be removed or covered with fine <br />grained material. <br />2. If there is any question, based on rock configuration exposed at <br />the surface, whether a rock would pass a 2 inch sieve, the rock <br />must be removed from the fill and loaded-out of the lined area. <br />