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August 37, 1994 Mr. Berhan Keftelew Environmental Protection Specialist Colorado Department of Natural Resources Division of Mines and Geology Office of Mined Land Reclamation 1313 Sherman Street, Room 215 Denver, Colorado 80203 Reference: Geomembrane oertormance when placed directly on prepared soil liner fill containing soil materials 6etween_the 3/4-inch and 2-inch fraction at the surface. Dear Mr, Keffelew, The following report contains the resuks of static heap overburden loading of liner cover fill placed directly on a 80-mil VLDPE geomembrane, underlain by soil liner fill (ironclad tailings) that contained two approximately 2-inch size gravel pieces placed directly at the interface surface. The samples of liner cover fill, geomembrane, soil liner fill and 2-inch size gravel pieces were obtained from project specific materials that were either removed from the placed fill or from stockpiles. Additionally, the surface of the soil liner fill was sloped to simulate conditions that may occur on the side slopes of the pad during loading. A 10-inch diameter percolation cell was used to confine the layers of drain cover fill, VLDPE, and soil liner fill. The composite layers were subjected to a static load of 300 psi (approximately 375 feet of equivalent ore) overnight. The cell was then dismantled and the VLDPE was evaluated for deformation and damage. The purpose of this type of large scale performance testing is to determine what, if any, mechanical damage will occur to the geomembrane when subjected to maximum static heap loading conditions. SAMPLE PREPARATION Samples were placed in the cell in a condition similar to placement on the pad. Soil liner fill was near optimum moisture content and compacted to a wet density of approximately 141 pounds per cubic foot. That value is consistent with field measurements of soil liner fill recently obtained during construction. The sample of soil liner fill was obtained from the heap leach pad after the fill had been dumped from a truck and prior to compaction. The sample generally contained materia{ that was less than 3/4-inch in size but consistent with the material being placed on the pad, contained some gravel pieces between the 3/flinch and 2-inch fraction. The gravel pieces were obtained from material that was considered to 6e "reject' material from the surface of the soil liner fill during the site inspection on 8!29/94. A sample of the drain cover fill was obtained directly from Heap Leach Pad No. 2. The material contained material less than 1-inch and was generally well graded to the sand traction. The geomembrane sample was obtained from a roll of smooth 80-mil VLDPE that had been delivered to the project site from which a 10-inch diameter test specimen was cut_ TEST CONFIGURATION