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Water Inflow L Dischartte <br />• Previous hydrologic reports have given evidence that the inflow of <br />water to the mine can be attributed to dewatering of a perched <br />aquifer as well as surface water infiltration along the faults of <br />the graben. During idle years a clear picture of mine water inflows <br />was obtained because water that collected in the faces was regularly <br />pumped to NPDSS point 002 end discharged. The quantity of water <br />discharged was recorded on a meter and a correlation with <br />precipitation was made. The steady decrease in the amount of water <br />pumped from the mine during the idle years is evidence of the <br />creation of a dewatered zone in the saturated coal strata. The <br />decrease is also evidence that there is little communication with <br />the comparatively large aquifer within the Sast Salt Creek alluvium <br />across the west fault of the graben. <br />With the resumption of mining, water was not discharged from the <br />mine; rather, water was used during the mining cycle or stored in <br />sumps underground. No water has been discharged from the mine to <br />NPDBS Point 002 since April of 1987. The water that infiltrated the <br />mine was used for dust suppression in the mining cycle. <br />When mining resumed, additional area in the saturated portion of the <br />graben was opened increasing the flow of water into the mine. The <br />inflow of water went from a low of 0.80 gpm in 1988 to a high of <br />3.87 gpm in 1990. Water flowing downdip into the faces was pumped <br />to the sump and used. On April 27, 1990 Section 001 was abandoned <br />• and sealed. Water used for mining and at the offices is now being <br />trucked to the mine. Table 1 gives a month by month total of the <br />water trucked to McClane Canyon. <br />Nearly all of the water that had been generated within the mine came <br />from 001 North Section. The lowest portion of this section was <br />sealed in 1990 and no water has been produced in other areas of the <br />mine since then. The area behind the seals in 001 North Section <br />could still be experiencing an inflow of water. The volume of the <br />thousand foot long sealed section is equivalent to 14 million <br />gallons. At the rate of inflow being experienced in 1990, 3.9 <br />gallons per minute, it would take about seven years for the sealed <br />area to become totally full of water. <br />Source of Water Inflow <br />As detailed in previous reports, the water flowing into the mine <br />seems to be a mix of water infiltrating the graben along the faults <br />and water in the coal seam. The zone of saturation of the coal seam <br />was initially estimated using the results of exploration drilling. <br />The drilling indicated that holes in the McClane graben were dry; <br />specifically, holes 7-15-3 end 7-21-1. Additionally, a piezometer <br />installed downdip from the mine outside of the graben has not <br />realized water to date. Since the well is down-dip and is dry, Salt <br />Creek surmises that the water flowing into the mine is from a <br />• perched aquifer in the area of the coal mine. <br />Page - 2 <br />