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of Sylvester Gulch. This application originally requested approval to permanently <br /> dispose of 1.77 million tons of coal processing waste within the proposed structure. <br /> The original design phased the refuse pile into five specific design layouts (Phases I <br /> through V), including recompaction and reconfiguration of temporarily stored waste <br /> material. The pile was constructed according to this original phased design until the <br /> Phase IV configuration. A revision application was submitted in November 1992, <br /> which eliminated Phase V and reduced the pile to 1.2 million tons. The proposed <br /> storage volume represents a 15.7 year life. The proposal included the combination of <br /> a 28,500 cubic yard topsoil pile during Phases I through III and a maximum of 45,000 <br /> cubic yards of non-toxic soil cover (subsoil) stockpile. Topsoil removed for Phase IV <br /> will be stored on the 50-foot bench constructed in Phase III. In addition, an access <br /> road was constructed in Phase Three and a portion of the Sylvester Gulch access road <br /> to the main fan portal was relocated. Underdrains have been constructed beneath the <br /> pile. Piezometric groundwater monitoring will be conducted. Slopes of the pile will <br /> be maintained at 2.5H:1V. <br /> The permit revision application included a thorough slope stability analysis performed <br /> in accordance with the prudent state-of-the-art slope analysis for the original design in <br /> 1985. and for the redesigned pile in 1992. Material strength values were derived from <br /> on-site sample testing and nearby previously reported test results. Piezometer <br /> observations, falling head parameter tests and analytical projections were completed in <br /> order to predict appropriate phreatic surfaces within the proposed waste structure. <br /> Data for the 1992 analysis utilized data collected for the 1985 analysis. <br /> The applicant has committed to the installation and quarterly monitoring of three sets <br /> of survey monuments to monitor slope stability of the waste structure. One row of <br /> monuments has been installed parallel to the state highway adjoining the toe of the <br /> waste pile on 100-foot intervals. Two additional rows of monuments have been <br /> installed perpendicular to the highway on the facial slope of the pile at 50-foot interval <br /> spacing. The operator has also committed to quarterly reporting of visual inspections <br /> of the topsoil, non-toxic soil cover stockpiles, and refuse pile. <br /> For the Lower Permanent Waste Pile, drainage will be controlled by a series of <br /> drainage ditches, terraces, and a sedimentation pond. Since the pile will be <br /> constructed in phases, the drainage system will also be built in phases. All disturbed <br /> area drainage from the topsoil piles, subsoil stockpile and waste pile will be routed to <br /> the sedimentation basin at the northwest comer of the lower waste pile (MB-2R). <br /> The design incorporates several permanent drainage features into the plan. After final <br /> reclamation of the pile, the terraces will be barricaded with rocks or berms to prevent <br /> access to the pile. However, the terraces will still function to control runoff from the <br /> pile. A hundred year diversion ditch has been constructed around the perimeter of the <br /> pile to permanently collect any runoff from the site and safely route it to the natural <br /> drainage system. For a discussion of the hydrologic effects of the waste pile on both <br /> surface and groundwater, see the hydrology section in the Probable Hydrologic <br /> Consequences section of this findings document. <br /> 50 <br />