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• Maos <br />Two maps are included in this volume (Tab 6). They are presented to show the bore hole and <br />section locations. Two of Maxim's reports analyzed the stability of the site. The report in Tab 3 <br />evaluates stability at two sections (A and B). These sections were evaluated to determine if the <br />reclaimed portal area would be stable. The report in Tab 4 evaluates stability at four sections (], <br />2, Station 61 and 76). Sections 1 and 2 were taken to evaluate the stability of the topsoil <br />stockpile. Sections at portal road stations 61 and 76 were taken to evaluate the stability at critical <br />(high cut or fill) areas. <br />Expansive Soil Evaluation -Reclaimed Fill Sloues <br />Additional laboratory testing was performed (Tab 7) on typical material that will comprise the <br />reclaimed fill slopes to evaluate the expansion potential of the material. Swell-consolidation tests <br />were performed on the samples to evaluate the expansion potential when the material is subject to <br />innundation with results of no expansion and only slight consolidation. It is Maxim's opinion that <br />"properly prepazed reclaimed fill slopes will have adequate shear strength for stability of the slope <br />and that wetting of the fill material through natural precipitation and runoff will not adversely <br />affect the soil strength". <br />BRL commits to properly prepare the fill slopes which will entail placing the fill at or above <br />optimum moisture content and compacting the fill to a density of at least 85% of the maximum <br />modified Proctor density. <br />Additional Geotechnical Investigations -Coal Ivfine Waste Bank <br />Additional geotechnical investigations were performed at the site on January 24, 1997 (Tab 8). The <br />target material for the investigation was Mancos shale. WESTEC's report states in part: "Maxim <br />conducted consolidated undrained (CLT) triaxial tests on the Mancos Shale. These tests indicated a <br />cohesion of 1,100 psf and a 12 degree angle of internal friction. It is important to note that these tests <br />were conducted under saturated conditions. The Mancos Shale however, is not saturated in the waste <br />bank location, and therefore, the Maxim results are not representative of the site conditions." <br />WESTEC reevaluated its stability analysis of the proposed coal mine waste bank based on laboratory <br />derived strength pazameters. The stability results calculated with the revised material strength <br />parameters yielded higher factor of safety values than WESTEC's original coal mine waste bank <br />design report presented in Volume N. Therefore, the DMG's wncerns regarding the stability of <br />the coal mine waste bank should be alleviated. <br />• <br />-5- 2/13/97 <br />