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West Elk Mine lJ Table 62 Summa of Estimated Probable and Worst Case Groundwater Inflow to the Mine 1994 Estimate Probable Maximum "Worst Case" Maximum Inflows Inflows Item Initial Steady Initial Steady F Seam, 5-Year Mine Plan 1991-1998 99 184 Observed Inflow, F Seam 1982-1988 35 11.5 Life of Mine Estimates 719 • Approximate Apache Rocks Mining Area (E Seam) Longwall Panels (34,033,750 ft z) and Development Areas (11,286,750 ft?) • Approximate Jumbo Mountain Mining Area (B Seam) Longwall Panels (17,005,000 ft.z) and Development Areas (7,475,000 ft 2) • B and E Seam longwall mining panels aze 100 percent open (panel azeas defined above represent the gross area of longwall panel boundaries where all coal material were removed). • B and E Seam development areas aze 50 percent open (development areas defined above • represent the gross area of mains and development mining around the longwall panels where room-and-pillaz mining where approximately half of the coal materials were removed). • F Seam mining thickness (6 R.) • Approximate F Seam Mining Area is 2.5 mi.2 (69,696,000 ft?) • F Seam Mining Area is 50 percent open (F Seam mining was by the room-and-pillar method and a general assumption of 50 percent removal from these gross mining areas was assumed). • Half of the mining thickness is pore space following subsidence (i.e., only 50% of the volume of coal materials removed is considered available to be filled by water because much of the void space has been transferred vertically into the fractures and collapse azeas above the mine workings after mining). • Average estimated sustained inflow into the combined B and F Seam mine workings (7 gpm) or (491,872 ft s/yr.) • Average sustained inflow (1983-1995) observed into the mine (4.7 gpm, 7.54 AF/yr or 328,464.8 ft.3/yr.) • Maximum observed inflow into the mine workings (50 gpm) or (3,513,369 ft s/yr.) No seepage or outflow from the mine workings occurs. 1.05-210 Revised November 2004 PRIO