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2.3 Red Wash Alluvial Monitoring Program <br />Portions of Red Wash have experienced subsidence due to longwall mining at the <br />Deserado Mine. As required by CMLRD (now DRMS), BME initiated a detailed hydrology <br />monitoring program in Red Wash above the first longwall panel to be mined. The <br />monitoring program consisted of nine (9) holes drilled in the Red Wash alluvium across the <br />predicted zone of subsidence from longwall panel 1 (LW-1 ). Water levels in the holes were <br />monitored before, during, and after active subsidence took place. The purpose of the <br />monitoring program was to determine if surface flow in Red Wash was being lost to bedrock <br />as the result of subsidence. <br />The monitoring data, analysis and conclusions reached were submitted to CMLRD in an <br />Interim Report, November 1987, and in the Third Annual Hydrology Report, January 1988. <br />The purpose of the monitoring program was met in that it was determined that surface flow <br />in Red Wash was not lost to bedrock as a result of subsidence. The major conclusions of <br />the study were: <br />• Recharge of the basal alluvium was from the upper sandstone facies (bedrock) <br />and not from infiltration of surface runoff. <br />• Subsidence cracks in Red Wash as the result of longwall mining were quickly <br />filled with clay and silt preventing loss of surface water flow to bedrock. <br />Longwall mining of panel 2 (LW-2) passed under Red Wash in September 1988. The <br />surface elevation subsided approximately 3.7 and 4.1 feet at RW-7 and RW-9 respectively. <br />Events in Red Wash over LW-2 were expected to occur in the same fashion as those seen <br />over LW-1. The subsidence trough was developed and any subsequent flow in Red Wash <br />was expected to form a pond. The pond would trap sediments carried in the flow(s) until <br />full, at which time flow in Red Wash would likely resume flowing in a relatively narrow active <br />channel. <br />The conclusions noted above were further confirmed during 1989. On July 29, 1989 a large <br />flow event occurred in Red Wash. The subsidence trough over LW-2 filled with water. The <br />trough over LW-1 also filled, but to a lesser depth as it had filled with sediment in the past. <br />Water level measurements were taken in the monitoring holes while standing water <br />surrounded them. Readings had been taken only 18 days before. Even though the holes <br />were surrounded by standing water (approximately 3 and 4 feet deep at RW-7 and RW-9 <br />respectively) the alluvial water depths had still decreased. <br />Although the purpose of the monitoring program was met, BME continued to monitor the <br />Red Wash alluvial holes until water year 1996-1997. The latest monitoring results are <br />12 <br />