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the area of disturbance, no surface water impacts are anticipated. <br /> Impacts to the surface water system for mine water discharges have been <br /> experienced. High TDS (>5,000 mg/1) in the discharge water led to failure of <br /> Whole Effluent Toxicity (WET) tests from 1989 through mid 1993. The WET <br /> tests were performed in cooperation with the Colorado Water Quality Control <br /> Division (WQCD). WFU has taken the following measures to reduce the <br /> toxicity of the effluent: <br /> • On-site aeration structures were installed for HxS removal before <br /> discharging the effluent. <br /> • A pilot test was conducted to identify a flocculent for removing high levels <br /> of oil and grease from the effluent. <br /> • The main water source of the mine was changed from the high TDS <br /> (>5,000 ppm) alluvial well water to a significantly lower TDS (500 ppm) <br /> surface lagoon. <br /> • The raw water tank was thoroughly cleaned and disinfected to remove <br /> sludge built up over years. The sludge was found to contain significantly <br /> high levels (1,000 colonies/ml) of bacteria. <br /> • An MSHA waiver was received to stop the use of Wendon Dustrol-10 <br /> surfactant in the water spray at the longwall face. The surfactant has been <br /> found to be lethal to fish life at 500 ppm. <br /> These measures were apparently effective in remedying the problem, as WET <br /> testing failures have not occurred since the second quarter of 1993. <br /> Subsidence from underground mine workings could potentially impact both Red <br /> Wash and Scullion Gulch. The effect on Red Wash is of greatest importance <br /> because it drains approximately 122 square miles at the location where mining <br /> will extend beneath it. Although predictions indicate that maximum vertical <br /> subsidence could approach six feet, large crevasses or collapse of the surface <br /> should not occur because there is approximately 600 to 1200 feet of overburden <br /> above the coal seam in that area. Furthermore, the swelling of shales and <br /> overburden from the caved roof should effectively fill the open mine cavity. <br /> An ongoing monitoring program was implemented to detect subsidence on the <br /> first longwall panel and first room-and-pillar section to be mined during the <br /> initial years of production. Predictions of probable disruption of the hydrologic <br /> regime from subsidence were based on an analysis of those data. The permittee <br /> originally predicted that tension cracks from subsidence may develop in <br /> formations directly underlying Red Wash and that these cracks may extend <br /> upward for several tens of feet. These cracks were predicted to be of limited <br /> extent; therefore, a minimal amount of surface water was predicted to be <br /> 24 <br />