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A RCOSA <br /> Geolo-gy <br /> Material to be mined as feedstock for the lightweight aggregate processing plant is shale of Cretaceous <br /> Age contained in the Pierre Shale Formation. This bedded shale formation dips an average of 56 <br /> degrees toward the east at the quarry site and is interspersed with thin beds of limey sandstone and <br /> relatively small concretionary calcareous lenses. The Pierre Formation at this location is approximately <br /> 8,000 feet thick.As shown in Figure D.6, the quarry in cross section only penetrates a small fraction of <br /> the formation. The shale is generally dark greenish-grey to black in color, is well consolidated, quite soft <br /> and contains approximately 10% inherent moisture. Additionally, the material deteriorates rapidly when <br /> exposed to the natural elements, precluding any possibility of maintaining more than a few days'surge <br /> between mine and plant. Sufficient reserves are available within the permit area to sustain plant <br /> operations for in excess of 30 years. <br /> Overlying the Pierre Formation at the Hogan property is 5 to 20 feet of bouldery sand and gravel <br /> containing abundant granite and gneiss. Material in this surface feature, called the second Coal Creek <br /> Berm, is of Quaternary Age, and is strongly weathered. The gravel was deposited by the present <br /> drainage system when it was flowing at a higher level. <br /> Waste Disposal <br /> Disposal of solid wastes from the processing plant's lime flue gas scrubbing system will be ancillary to <br /> routine mine operations. The anticipated composition of the waste material is: <br /> 50% Raw Shale Fines <br /> 38% Gypsum (CaSO4.2H2O) <br /> 10% Flyash <br /> 2% Unreacted Lime <br /> This material will be trucked from the plant site in a relatively dry state(15% moisture)at an estimated <br /> rate of approximately 50 to 70 tons per day. The material will be placed along the contours of the <br /> sidewalls of the portion of the quarry that is undergoing contemporaneous reclamation at that time. The <br /> material is placed along the sidewall via dozer pushing the solid waste material over the edge of the <br /> quarry sidewall allowing the material to slope down the side of the quarry. Since the material is placed <br /> within the impervious Pierre Shale Formation, potential leachates should be contained to within the <br /> quarry. <br /> To verify that leachate from the waste material has not impacted local groundwater conditions, a <br /> groundwater monitoring well will be drilled at least 20 feet below the quarry floor elevation of 5,860 feet <br /> above mean sea level hydrologically down gradient of the quarry. The monitoring well will be screened <br /> across the lowest 50 feet of well conduit. Groundwater is not anticipated to be encountered due to the <br /> impervious nature of the Pierre Shale Formation as discussed further below. The well will be monitored <br /> on a quarterly basis for the first two(2)years following its installation. If no parameters are identified <br /> above applicable regulatory limits during the first two(2)years of monitoring,the well will then be <br /> monitored on a semi-annual basis for an additional two(2)years. If no parameters are identified above <br /> applicable regulatory limits during the two(2)years of monitoring on a semi-annual basis, the well will <br />