Laserfiche WebLink
1 <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 />I 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 of <br />the monitoring program was met in that it was determined that surface flow in Red Wash was not <br />last to bedrock as a result of subsidence. The major conclusions of the study were: <br />' • Recharge of the basal alluvium is 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 are quickly filled with <br />clay and silt preventing loss of surface water flow to bedrock. <br />t Although the purpose of the monitoring program has been met, Western Fuels is continuing to <br />monitor the Red Wash alluvial holes. The monitoring results are reported in Appendix F and <br />hydrographs for each monitoring hole are presented in Appendix G. <br />Longwall mining of panel 2 (LW-2) passed under Red Wash in September 1988. The surhace <br />elevation has 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. The <br />subsidence trough was developed and any subsequent flows in Red Wash was expected to form <br />a pond. The pond would trap sediments carried in the flow(s) until full, at which time flows in Red <br />Wash would likely resume flowing in a relatively narrow active channel. <br />' The conclusions noted above were further confirmed during 1989. On July 29, 1989 a large flow <br />event occurred in Red Wash. The subsidence trough over LW-2 filled with water. The trough over <br />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 standing <br />water (approximately 3 and 4 feet deep at RW-7 and RW-9 respectively) the alluvial water depths <br />had still decreased. <br />Again this year, very little change in the water levels was recorded. Three monitor holes (RW1. <br />RW2, RW8) experienced slight rises in water level. RW-4 shows a fluctuating water level, possibly <br />' from being disturbed as noted in the report for last year. <br /> <br />' 14 <br /> <br />