2012-01-26_PERMIT FILE - C1981018A

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Monitoring of wells 2 -7TWU, 2 -7TWL, 2 -7U, 2 -7M, 2 -7L, 35-4U, 35-4L, 354M, 36 -2U, 36 -21- and RM -1 was discontinued pursuant to DMG's approval of TR48. Monitoring was discontinued because these holes were either dry or did not serve any purpose. Upper sandstone wells will not be plugged without DMG's prior approval. They will be retained to allow for monitoring associated with bond release. Siltstone -coal Facies and Lower Sandstone wells may be plugged prior to or after being mined through to avoid safety concerns with open communications between the surface and mine workings. Such plugging will only occur after the final required sampling has taken place. Alluvial monitor hole Qal -5 is periodically monitored to measure impacts to the White River's alluvial aquifer from the mine's production water well field. With the flooding of the Kenney Reservoir the mine abandoned pumping from the well field and began pumping directly from the river. Nine (9) new alluvial monitoring holes were installed in Red Wash (see Map 137) during the spring or summer of 1986. These holes were installed to monitor water levels during mining of Longwall Panel No. 1. After installing these holes, water levels were measured once every two months. When the longwall face has advanced to within 200 feet of the Red Wash alluvium, water level monitoring was done once every two weeks and continued on this schedule until the longwall face had advanced past the alluvium 400 feet. Thereafter, monitoring resumed at a schedule of once every two months until longwall mining in panel 1 was complete. Results of the Red Wash monitoring have been reported in the Deserado Mine Annual Hydrology Report, and in an Interim Report submitted to CMLRD in November 1987. The purpose of the Red Wash alluvial monitoring program was to determine whether surface flow in Red Wash would be lost to bedrock as a result of subsidence. The major conclusions of the program were: • Surface flow in Red Wash is not lost to bedrock as a result of subsidence. • Recharge of the basal alluvium is from the upper sandstone facies (bedrock) and not from infiltration of surface runoff. • Subsidence cracks in Red Wash are quickly filled with clay and silt preventing any loss of surface water to bedrock. • Water ponding in the subsided area acted as a stilling basin for deposition of clays and silts being carried down Red Wash. This provided a beneficial impact in that the sediment load to the White River was reduced. Since these wells RW -1 through RW -9 satisfied their intended study purposes, monitoring requirement of these wells was eliminated in 1997 by DMG in response to a technical revision. It is expected that future subsidence from longwall mining under Red Wash and Scullion Gulch will have similar effects as those observed during this monitoring program. Minor Revision #149 (01/2012) II.0 -7 7