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• 2003 AHR McClane & Munger Canyon Mines Page 2 Mine Water Inflow/Discharge Appendix N of the permit application indicates the rate at which the saturated coal ribs are exposed should govern the maximum mine inflow rate. A five entry system exposes 1,480 lineal feet of rib per 100 feet of advance assuming 80 foot square pillars. That same 100 feet of development produces 5,400 tons of coal assuming an eight foot mining height. Based upon the k factor of 0.11 feet per day, it takes about one year to dewater an 80 foot square pillar (40 feet / 0.11 feet per day). Therefore, exposed coal ribs contribute to mine inflow for one year. At an annual production rate of 0.3 million tons per year, using this five entry system, a total of 5,500 feet of development would be required. This would expose 81,000 [(1,480)(5,500)/100) feet of rib. This amount of exposed rib would produce an estimated maximum mine inflow as follows q = kia = (0.11) (81,000 x 8) (0.05) = 3,600 cubic feet per day a 20 gpm. Water was discharged from the mine during the reporting period. During the hot summer months the mine discharge can be utilized to water roads. Flows into the mine are estimated in Table 1. Previous hydrologic reports have shown the inflow of water to the mine can be attributed to dewatering of a perched aquifer as well as surface water infiltration along the faults of the graben. During the mid 1980's, a clear picture of mine water inflows was obtained because water collected in the faces was regularly pumped to outfall 002 and discharged. The quantity of water discharged was recorded on a meter and correlated with precipitation. The steady decrease in the amount of water pumped from the mine during the idle years is evidence of the creation of a dewatered zone in the saturated coal strata. This decrease also provides evidence there is little communication with the comparatively large aquifer within the East Salt Creek alluvium across the west fault of the graben. When mining resumed, additional area in the saturated portion of the graben was exposed, increasing the flow of water into the mine: The inflow of water went from a low of 0.80 gpm in 1988 to a high of 3.87 gpm. in 1990. Water flowing down dip into the faces was pumped to the sump and used in the mining process for dust control. On April 27, 1990, Section 001 was abandoned and sealed. A small amount of water was trucked to the mine for supply road dust suppression starting in October 1999 prior to production. When production resumed in February 2000 the demand increased to approximately 373,000 gallons per month. In April 2000 water started seeping from the mining faces developing to the east. To keep up with production demands, a sump was established and the section was moved to the south. The water in the North faces is currently pumped to the sump and again used in the mining process for dust control. During 2003 the inflow of water into the mine is estimated to be approximately 12.4 gpm based on the mine's demand for water and the amount of water discharged and consumed for dust suppression. This compares relatively good with the 20 gpm estimated mine inflow rate explained above. Table I provides a month by month total of the water pumped from the mine. Table 6 shows quality results of mine discharge sampling.