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The raw water tank was thoroughly cleaned and disinfected to remove sludge <br />built up over years. The sludge was found to contain significantly high <br />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 appazently 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 squaze miles at the location where mining <br />will extend beneath it. Although predictions indicate that maximum vertical <br />subsidence could approach six feet, lazge 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 azea. Furthermore, the swelling of shales and <br />overburden from the caved roof should effectively fill the open mine cavity. An <br />ongoing monitoring program was implemented to detect subsidence on the first <br />longwall panel and first room-and-pillaz section to be mined during the initial <br />years of production. Predictions of probable disruption of the hydrologic regime <br />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 />upwazd 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 />siphoned into them. Furthermore, the permittee predicted that sediment <br />accumulating in the cracks, and clays in the overburden would ultimately seal <br />them off from surface inflow. <br />Continued monitoring of Red Wash has confirmed the permittee's predictions. <br />As projected, subsidence in Red Wash initially resulted in water ponding in the <br />stream bottom. The high content of silt and clay carried by Red Wash rapidly <br />fills the ponds. The silt and clay layers have sealed any cracks that formed in the <br />alluvium as the result of subsidence. Water continues to flow in the surface <br />channel at Red Wash while piezometric levels in the basal alluvial gravel have <br />dropped, indicating that the basal alluvium is not rechazged by surface flow <br />infiltration. <br />Minimal subsidence impacts are expected on Scullion Gulch, similaz to those <br />observed on Red Wash. Thickness of overburden is much less under Scullion <br />Gulch than Red Wash. The Staley-Gordon Mine, abandoned in 1970, has only <br />200 to 300 feet for overburden thickness, compazable to that under Scullion <br />Gulch in the Deserado Mine. No surface expressions of subsidence have been <br />noted over caved areas in the Staley-Gordon Mine. Examination by Western <br />'i0 <br />