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The overburden analyses did reveal SAR values exceeding soil suitability criteria defined <br />in Wyoming DEQ Guideline No. 1; however, this concern is ameliorated by replacement <br />of cover soi148 inches thick on RP-1, and at least 30 inches thick on other refuse areas. <br />The Division has approved a cover replacement thickness of less than 4 feet, based on <br />physical and chemical analyses of the refuse material, and further based on results of a five <br />year "Refuse Area Revegetation Study" focusing on effects of varying cover thickness. <br />The study final report was completed in December, 1996, and is included as Appendix A, <br />of Section V, Vol. 4, of the permit application. Study results and analyses demonstrated <br />that the requirements of Rule 4.15 can be met with less than four feet of refuse cover <br />material (4.10.4(5)). <br />The refuse disposal area is divided into I 1 subareas. At the time the initial permit was <br />approved, the permittee anticipated that only approximately ten acres would be in use at <br />any one time to minimize the total disturbed azea. However, some time after permit <br />approval, when refuse disposal operations got underway, it became appazent that <br />additional acreage would need to be developed in order to provide sufficient room for the <br />drying of refuse to attain the appropriate moisture percentage necessary to meet <br />compaction requirements. As a result, a technical revision to the permit was approved by <br />the Division on September 26, 1985, which allowed Western Fuels to open an additional <br />pair ofsub-areas (Nos. 2 and 3) ahead of schedule to provide additional room for the <br />drying of refuse. With the approval of the technical revision, the maximum anticipated <br />disturbed azea (excluding reclaimed acreage) at any one time has been increased to 120 <br />acres. Refuse Areas 2, 3, and 4 were subsequently combined into a single disposal pile <br />(RP-2/3/4). <br />During construction, the refuse piles aze inspected quarterly and the proper placement <br />certified by a registered professional engineer in compliance with Rule 4.10.2 of the <br />Colorado Permanent Regulatory Program. <br />A surface water control system has been constructed for use during the development of the <br />refuse piles and subsequent to reclamation of the piles. See the Surface Water section of <br />this Findings Document. <br />The face slopes on Refuse Area RP-1 was constructed with a Sh:1v slope. Refuse Areas <br />2/3/4 and SA will be constructed with a maximum 4(h):ly slope. Illustrations 21, 42, and <br />42A of the approved permit application present original geotechnical field investigation <br />and stability analysis, and subsequent testing of waste material and reevaluation of pile <br />stability. RP-2/3/4 was originally approved with 5:1 slopes, but final reclamation designs <br />were amended in association with RN-03, to specify 4:1 maximum slopes. Based upon <br />the previously approved laboratory and analytical information, the Division has <br />determined the steepening of the RP-2/3/4 structure to a facial angle not to exceed 4h:1 v, <br />to be acceptable. As long as the structures comply with the approved height limitation <br />(i.e., 100 feet total vertical height) the pile will comply with regulatory specifications <br />regarding slope stability. The stability of this slope was found to meet the requirements of <br />a safety factor of 1.5. Foundation materials were also found to be stable under the weight <br />of the refuse material. This slope will also facilitate the post-mining land use of grazing <br />~F <br />