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• 2008 AHR McClane & Munger Canyon Mines Page 2 <br />dewater an 80 foot square pillar (40 feet / 0.11 feet per day). Therefore, exposed coal <br />ribs contribute to mine inflow for one year. At an annual production rate of 0.3 million <br />tons per year, using this five entry system, a total of 5,500 feet of development would be <br />required. This would expose 81,000 [(1,480)(5,500)/100] feet of rib. This amount of <br />exposed rib would produce an estimated maximum mine inflow as follows q = kia = <br />(0.11) (81,000 x 8) (0.05) = 3,600 cubic feet per day = 20 gpm. <br />Water was discharged from the mine during the reporting period. During the hot <br />summer months the mine discharge is utilized to water roads. Flows into the mine are <br />estimated in Table 1. Previous hydrologic reports have shown the inflow of water to the <br />mine can be attributed to dewatering of a perched aquifer as well as surface water <br />infiltration along the faults of the graben. During the mid 1980's, a clear picture of mine <br />water inflows was obtained because water collected in the faces was regularly pumped <br />to outfall 002 and discharged. The quantity of water discharged was recorded on a meter <br />and correlated with precipitation. The steady decrease in the amount of water pumped <br />from the mine during the idle years is evidence of the creation of a dewatered zone in the <br />saturated coal strata. This decrease also provides evidence there is little communication <br />with the comparatively large aquifer within the East Salt Creek alluvium across the west <br />fault of the graben. <br />When mining resumed, additional area in the saturated portion of the graben was <br />exposed, increasing the flow of water into the mine. The inflow of water went from a low <br />• of 0.80 gpm in 1988 to a high of 3.87 gpm in 1990. Water flowing down dip into the <br />faces was pumped to the sump and used in the mining process for dust control. On April <br />27, 1990, Section 001 was abandoned and sealed. <br />A small amount of water was trucked to the mine for road dust suppression starting in <br />October 1999 prior to production. When production resumed in February 2000 the demand <br />increased to approximately 373,000 gallons per month. In April 2000 water started seeping <br />from the mining faces developing to the east. To keep up with production demands, a sump <br />was established and the section was moved to the south. The water in from the east end of <br />the East Mains is pumped to a sump and again used in the mining process for dust control. <br />During 2008 the inflow of water into the mine is estimated to be approximately 15.1 gpm <br />based on the mine's demand for water and the amount of water discharged and consumed <br />for dust suppression. This compares favorably with the 20 gpm estimate provided above. <br />Table 6 shows quality results of mine discharge sampling. <br />As discussed in previous reports, the area in the mine that experienced an inflow of <br />water was sealed in 1990. In July of 1992 all areas to the north of the East Mains were <br />sealed and are now inaccessible. Figure 3, McClane Mine Map shows the location of the <br />seals; as well as, the area of the mine that is not accessible. The sealed area is lower in <br />elevation than accessible areas of the mine but is undoubtedly still experiencing an inflow <br />of water. The volume of the portion of the mine behind the seals is equivalent to about <br />124 million gallons. At the rate of inflow being experienced in 1990, 3.9 gallons per <br />minute, it would take about 60 years for the sealed area to fill with water. <br />0 <br />Rev. 08/09