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To date refuse piles have not impacted the groundwater zone <br /> near Sylvester Gulch. Because of the low permeability of the <br /> colluvial soils and the lack of a groundwater table near the <br /> surface in the colluvium, no impacts on groundwater are <br /> anticipated. Water monitoring wells SGA and RPE-1, located <br /> near the site of the soil stockpiles, other water quality <br /> monitoring stations on Sylvester Gulch, and sites above and <br /> below the mine on the North Fork of the Gunnison, provide <br /> sufficient baseline water quality information to evaluate the <br /> changes in water quality that could result from the impacts of <br /> this refuse stockpile. An additional groundwater monitoring <br /> well is scheduled for installation in the alluvial deposits <br /> downgradient of the RPE area. Conductivity and TDS from <br /> samples of monitoring well GP-1 showed slightly higher levels <br /> in 1986. However, this does not appear to be a continuing <br /> problem. Concentrations of iron during 1991 were higher than <br /> the baseline monitoring data, which the operator believes may <br /> be associated with B development waste. Concentrations of iron <br /> will be monitored to see if the elevated levels continue. <br /> A leachate study of the F Seam refuse was conducted and <br /> included in the application for the permanent refuse disposal site <br /> in Exhibit 51 of the permit application. In addition, the effects <br /> of B Seam refuse on leachate were also evaluated and can be <br /> found in Exhibit 56. The permeability contrast found in the pile <br /> will cause most of the leachate water to perch within the refuse <br /> pile and above the native soils. A shallow water mound will <br /> build within the pile and cause the water to migrate laterally to a <br /> small seepage area at the edge of the site. During 1991, there <br /> were no visible flows from the pile toe and midsection <br /> underdrain. <br /> Upper Refuse Disposal Area - The upper waste rock pile was <br /> approved, with stipulations on June 14, 1986. This pile has not <br /> been constructed and construction is not proposed for this permit <br /> term. The final pile would cover approximately 40 acres and <br /> contain five million tons of coal reject and developmental waste <br /> rock. The primary predicted impact to groundwater would be <br /> the development of leachate from precipitation infiltration <br /> through the pile. The approved plan calls for the installation of <br /> five lateral subdrains to collect this leachate. The drains will <br /> help prevent the formation of a large perched leachate aquifer <br /> that may effect the stability of the pile. Additionally, the drains <br /> will intercept most of the leachate and prevent it from entering <br /> the shallow colluvial aquifers. The subdrains will daylight into <br /> 41 <br />