2009-02-10_PERMIT FILE - C1981022 (5)

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Sea n- 2.04.7 searns, the following hydraulic characteristics have been estimated based on typical values presented in Applied Hydrogeology (Fedder, 1988): • Transnussivity- 0.90 to 0.96 • Porosity- 0.0012 • Aquifer Thickness - 2 to 14 feet I-L.storic mining operations have encountered perched ground water, with resulting mine inflows, from the E, D, C, and B coal seams or the associated overlying or underlying units. Continued mining operations are expected to encounter perched ground water from the B seam (Sanborn Creek Mme) and D seam (Elk Creek Mme) sequences. Recorded mine inflows to the Somerset Nine workings (B seam) were approximately 235 gpm and inflow rates were relatively consistent with no significant increase in discharge from caved areas following completion of pillar recovery and subsequent roof collapse. Inflows to the active Sanborn Creek Nine (B and C seams) average 100 gpnt, although interception of a fracture system resulted in a short-term increase in peak inflows to approximately 250 gpm and inflow potential has been calculated to be as high as 400 gpm The Oliver Mme was developed in the D seam, with most of the development upgradient from its outcrop/sub-crop with Elk Creek Available information indicates that the Oliver Mine workings were generally dry with isolated areas of limited mine inflow (0 to 6 gpm). The majority of the exploration drillholes completed in the mine area have been relatively dry, with occasional damp zones encountered in some of the holes and limited occurrences of actual flowing ground water. Drillholes SG 1, 2, and 3 were drilled in the vicinity of the Sanborn Creek Mme. Drillhole SG1 was essentially dry except for a damp zone at a depth of approximately 40 feet until it intercepted the Rollins sandstone. Drillholes SC-2 and SC-3 encountered ground water in both the D Coal Seam and Rollins sandstone. Mute inflow potential from the D seam below its outcrop/sub- crop with Elk Creek is un-quantified at this time but drilling results indicate that the seam does contain water in the vicinity of Elk Creek Inflow potential for the D, C, and B coal seams may be estimated using the following relationship that is based on Darcy s Law: Q - ((W)(T)"/(n)(L)) where; Q is steady-state flow rate (gpd) based on the total length of exposed coal face W is the width (h) of mine workings adjacent to the outcrop T is transmissivity (gpd/ft) H is potentiornetric head (ft) of potential recharge source above mining (Elk Creek above D seam and outcrop Isubcrop above C and B seams) n is coal seam porosity L is distance (ft) from mine workings to outcrop The results of this calculation for the respective coal seams or associated clastic sequences are as follow: Coal Seam ?) T ft H ft n L ft d/ m D 6,600 2.00 100 0.0012 2,400 458,330/318 C 17,495 0.90 200 0.0012 7,380 355,680/247 B 16,050 0.96 250 0.0012 12,074 265,860/185 Based on recorded mine inflows, the mine inflow estimates above are relatively accurate and can be used as a general indicator of anticipated inflow rates. • In most cases, the volume and rate of any perched ground water discharge at stratigraphic outcrops is limited. Because most of the perched ground water occurs in near-surface units, discharge is frequently ephemeral, flowing for a brief period following spring snowmelt until infiltration from PR04 2.04-26 Revised August 2000