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' drilled in the Red Wash alluvium across the predicted zone of subsidence from longwall panel 1 <br />' (LW-1). Water levels in the holes were monitored before, during and after active subsidence took <br />place. The purpose of the monitoring program was to determine if surface flow in Red Wash was <br />being lost to bedrock as the result of subsidence. <br />t The monitoring data, analysis and conclusions reached were submitted to CMLRD in an Interim <br />' Report, November 1987, and in the Third Annual Hydrology Report, January 1988. The purpose <br />of the monitoring program was met in that it was determined that surface flow in Red Wash was <br />not lost to bedrock as a result of subsidence. The major conclusions of the study were: <br />' • Recharge of the basal alluvium was from the upper sandstone facies (bedrock) and not <br />from infiltration of surface runoff. <br />• Subsidence cracks in Red Wash as the result of longwall mining were quickly filled with <br />' clay and silt preventing loss of surface water flow to bedrock. <br />Although the purpose of the monitoring program was met, BME continues to monitor the Red <br />' Wash alluvial holes. The monitoring results are reported in Appendix F and hydrographs for each <br />monitoring hole are presented in Appendix G. <br />' Longwall mining of panel 2 (LW-2) passed under Red Wash in September 1988. The surface <br />elevation subsided approximately 3.7 and 4.1 feet at RW-7 and RW-9 respectively. Events in <br />' Red Wash over LW-2 were expected to occur in the same fashion as those seen over LW-1. <br />The subsidence trough was developed and any subsequent flow in Red Wash was expected to <br />' form a pond. The pond would trap sediments caried in the flow(s) until full, at which time flow <br />in Red Wash would likely resume flowing in a relatively narow active channel. <br />' The conclusions noted above were further confirmed during 1989. On July 29, 1989 a large flow <br />event occured in Red Wash. The subsidence trough over LW-2 filled with water. The trough <br />' over LW-1 also filled, but to a lesser depth as it had filled with sediment in the past. Water level <br />measurements were taken in the monitoring holes while they were surrounded by standing water. <br />Readings had been taken only 18 days before. Even though the holes were surrounded by <br />t standing water (approximately 3 and 4 feet deep at RW-7 and RW-9 respectively) the alluvial <br />water depths had still decreased. <br />1 <br />1 <br />1 <br /> <br />17 <br />