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West <br />small diameter pipe is installed at the base of seals where water may accumulate, as required by <br />MSHA, to relieve pressure build-up from water accumulating on the seal. <br />Longwall mining of the 6NW and 7NW panels was completed in late February 1996 and these <br />panels were sealed, along with the already sealed 1NW through SNW panels, in June 1996. In <br />March 1996, development mining in the B East Mains encountered a fault system containing lazge <br />volumes of water. Initial inflows from the BEM Fault were estimated at 2,500 gpm with flows <br />eventually leveling out at less than 100 gpm. The unprecedented inflows coupled with the presence <br />of colloidal clay particles created treatment difficulties for TSS in the sedimentation ponds. At the <br />time, surface applications of alum provided the most effective treatment and allowed MCC to meet <br />discharge permit limits with only a couple of exceptions. <br />In November 1996, two key events occurred that forced MCC to alter their water management and <br />treatment practices. The first was a letter from the CWQCD stating that if MCC had additional <br />permit exceedances, then enforcement actions, including fines, would be assessed. The second was <br />that the sedimentation ponds were freezing over, thus rendering alum applications infeasible. These <br />two events led to the decision to pump the "dirty" water to the mined NW panels, thus creating the <br />NW Panels sealed sump. During this period, "clean" water from the B East Mains fault was <br />segegated and was pumped to and dischazged from the sedimentation ponds on the surface. <br />The storage capacity in the NW Panels sealed sump when the surface elevation of the water was at <br />the 1NW Tailgate seal in crosscut 14 was estimated to be 104 million gallons, or 318 acre-feet. This <br />• estimate of storage is based on the volume created by the extraction of the coal assuming a 20 <br />percent porosity of the mined area after subsidence and 100 percent porosity of the development <br />mining azea. <br />A preferred second estimate of the storage volume was made using athree-dimensional computer <br />representation of the NW Panels sealed sump. Using a collapsed material porosity value of 20 <br />percent and an 85 percent porosity of the development mining azea, the estimated storage volume <br />within the NW Panels sealed sump is 122 million gallons or 375 acre-feet. <br />In January 1997, the second large fault system was encountered in the 14SE Headgate (formerly <br />termed the 1SE Headgate). Initial inflows were estimated at 8,000 gpm; and MCC's emergency <br />procedures were implemented to protect the miners and save West Elk Mine. With the restrictions <br />on the sedimentation ponds noted above and discussed later, the majority of the fault inflows were <br />directed to the NW Panels sealed sump until eazly March 1997, when water was observed seeping <br />beneath, azound, and through the seals at crosscut 14 in the 1NW Tailgate; and, thus, the sump was <br />considered "full". <br />Periodic observations at the seals indicated that the water level in the sump remained relatively <br />constant, indicating that there was little or no loss of water occurring. The utilization of the <br />sump was geazed towazd enabling discharges to Lone Pine Gulch via a pipe through the <br />northern-most 7NW panel seals (a.k.a. Lone Pine seals). However, the water level reached the <br />seals in the 1NW Tailgate at crosscut 14 prior to having sufficient head at the Lone Pine seals for <br />• discharge. Consequently, the seals at crosscut 14 were replaced with new seals up-dip at crosscut <br />12 in the 1NW Tailgate. With this improvement, enough water could be pumped to the sealed <br />205-282 RevisedJw~e 2005 PRI0; Rev. March 2006; Rev. May 2006 PRIO <br />