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Mine Water Inflow / Dischart,~e <br />• No water has been discharged from the mine and no flow into the mine has been noted this <br />year. Previous hydrologic reports have shown that the inflow of water to the mine can be <br />attributed to dewatering of a perched aquifer as well as surface water infiltration along the faults <br />of the graben. During the mid 1980's, a clear picture of mine water inflows was obtained because <br />water that collected in the faces was regularly pumped to NPDES point 002 and discharged. The <br />quantity of water discharged was recorded on a meter and a correlation with precipitation was <br />made. The steady decrease in the amount of water pumped from the mine during the idle years is <br />evidence of the creation of a dewatered zone in the saturated coal strata. This decrease also <br />provides evidence that there is little communication with the comparatively large aquifer within <br />the East Salt Creek alluvium across the west fault of the graben. <br />When mining resumed, additional azea in the saturated portion of the graben was exposed, <br />increasing the flow of water into the mine. The inflow of water went from a low of 0.80 gpm in <br />1988 to a high of 3.87 gpm in 1990. Water flowing down dip into the faces was pumped to the <br />sump and used in the mining process for dust control. On April 27, 1990, Section 001 was <br />abandoned and sealed. Since then, all water necessary for operations has been trucked to the <br />mine. Table 1 gives a month by month total of the water trucked to McClane Canyon. <br />As discussed in previous reports, the area in the mine that experienced an inflow of water was <br />sealed in 1990. No water has been produced in other areas of the mine since then. In July of <br />1992 all areas to the north of the East Mains were sealed and are now inaccessible. Figure 2, <br />McClane Mine Map, shows the location of the seals; as well as, the area of the mine that is not <br />. accessible. The sealed area is lower in elevation than accessible areas of the mine but is <br />undoubtedly still experiencing an inflow of water. The volume of the portion of the mine behind <br />the seals is equivalent to about 124 million gallons. At the rate of inflow being experienced in <br />1990, 3.9 gallons per minute, it would take about 60 years for the sealed area to frll with water. <br />Only then will the mine realize a detectable inflow of water from the areas that had been making <br />water previously. <br />Source of Water Inflow <br />As detailed in previous reports, the water flowing into the mine seems to be a mix of water <br />infiltrating the graben along the faults and water in the coal seam. The zone of saturation of the <br />coal seam was initially estimated using the results of exploration drilling. The drilling indicated <br />that holes in the McClane graben were dry; specifically, holes 7-15-3 and 7-21-1. <br />Additionally, a piezometer installed down dip from the mine outside of the graben has not <br />realized water to date. Since the piezometer is down-dip and is dry it is apparent that the water <br />flowing into the mine is from a perched aquifer in the area of the coal mine. <br />The water within the perched aquifer flowing into the mine probably comes from surface <br />water infiltration along the faults east and west of the mine. Both faults have ephemeral drainages <br />crossing their surface trace. These faults may be one source of recharge to the perched aquifer. <br />The water then infiltrates the coal seam which has become saturated over time. This assumption <br />• is supported by the previously documented cyclical nature of water inflow corresponding with <br />periods of precipitation. <br />AHIt - 98 Page - 2 I 1 - 23 - 98 <br />