2014-01-14_REPORT - C1981020 (4)

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2013 AHR McClane & Munger Canyon Mines Page 2 CAM - Colorado, LLC has been granted a lease suspension. It is unknown how long the mine will remain idle. As required by stipulations, a mine map for McClane Canyon showing important hydrologic features is included as Figure 3. Seepage into the mine is nearly all from the areas mined to the north of the East Mains. Water from seeps accumulates in the east end of the East mains. In response to comments made by the Division regarding the 1995 annual hydrologic report, Figure I - Water Sampling Locations, is enclosed. Figure 1 is a line diagram of the drainages and water sampling locations that was derived from Figure 4.2 -2 of the McClane Canyon Mine permit. 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 = 20 gpm. Water was discharged from the mine during all months of 2013. 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