Laserfiche WebLink
<br />' The toxicity problem with the mine water was limited to the first longwall district. Mining in this <br />district was completed in early 1993. The district has since then been sealed underground. <br />' There has been no pumping of accumulated water from underground during this water year. <br />2.3 Red Wash Alluvial Monitoring Program <br />Portions of Red Wash have experienced subsidence due to longwall mining at the Deserado <br />' Mine. As required by CMLRD (now DMG), BME initiated a detailed hydrology monitoring <br />program in Red Wash above the first longwall panel to be mined. The monitoring program <br />' consisted of nine (9) holes drilled in the Red Wash alluvium across the predicted zone of <br />subsidence from longwall panel 1 (LW-1). Water levels in the holes were monitored before, <br />during and after active subsidence took place. The purpose of the monitoring program was to <br />' determine if surface flow in Red Wash was being lost to bedrock as the result of subsidence. <br />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 <br />purpose of the monitoring program was met in that it was determined that surface flow in Red <br />Wash was not lost to bedrock as a result of subsidence. The major conclusions of the study <br />were: <br />• Recharge of the basal alluvium was from the upper sandstone facies (bedrock) and <br />not from infiltration of surface runoff. <br />' Subsidence cracks in Red Wash as the result of longwall mining were quickly filled <br />' 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 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 carried in the flow(s) until full, at which time flow <br />in Red 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 <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 they were surrounded by <br />' standing water. Readings had been taken only 18 days before. Even though the holes were <br />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 />19 <br />