1997-05-05_GENERAL DOCUMENTS - C1980007

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To date the lower refuse pile has not impacted the ground water zone near Sylvester Gulch. Because of the low permeability of the colluvial soils and the lack of a ground water table near the surface in the colluvium, no impacts on ground water are anticipated. Water monitoring well SG-1, located near the site of the soil stockpiles, other water quality monitoring stations on Sylvester Gulch, and sites above and below the mine on the North Fork of the Gunnison, provide sufficient baseline water quality information to evaluate the changes in water quality that could result from the impacts of this refuse stockpile. Conductivity and TDS from samples of monitoring well GP-1 showed slightly higher levels in 1986. However, this does not appear to be a continuing problem. Concentrations of iron during 1991 were higher than the baseline monitoring data, which the operator believes may be associated with B development waste. Concentrations of iron will be monitored to see if the elevated levels continue. A leachate study of the F Seam refuse was conducted and included in the application for the permanent refuse disposal site in Exhibit 51 of the permit application. In addition, the effects of B Seam refuse on leachate were also evaluated and can be found in Exhibit 56. The permeability contrast found in the pile will cause most of the leachate water to perch within the refuse pile and above the native soils. A shallow water mound will build within the pile and cause the water to migrate laterally to a small seepage area at the edge of the site. During 1991, there were no visible flows from the pile toe and midsection underdrain. Upper Refuse Disposal Area - The upper waste rock pile was approved, with stipulations on June 14, 1986. This pile has not been constructed and construction is not proposed for this permit term. The final pile will cover approximately 40 acres and contain five million tons of coal reject and developmental waste rock. The primary predicted impact to ground water is the development of leachate from precipitation infiltration through the pile. The approved plan calls for the installation of five lateral subdrains to collect this leachate. The drains will help prevent the formation of a large perched leachate aquifer that may effect the stability of the pile. Additionally, the drains will intercept most of the leachate and prevent it from entering the shallow colluvial aquifers. The subdrains will daylight into surface channels where the leachate will flow to a sediment pond. As this pile is constructed, spoil wells will be installed. There are a number of stipulations which must be addressed prior to beginning the construction of the upper refuse pile. 37