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No areas of specific high inflows were found in the WMD. Also, because the panels where sealed sequentially <br />.after mining. the mine inflow surveys have never been able to include a synoptic survey of all of the panels. <br />Estimates based on a composite of several inflow studies and dewatering rates from indicate that approximately 55 <br />gpm resulted from this mining activity. Since the WMD has been sealed measurements of inflows and discharge <br />indicate the above rate to be a reasonable estimate. This inflow will be discussed further in the mine water-balance <br />discussion below. These inflows can be used to estimate overall inflows to the mine for areas that are no[ near the <br />subcrop of the coal. Based upon the estimated inflow of 55 gpm and an affected mine area of 2064 acres the <br />estimated inflow per unit area is 0.027 gpm/acre. An area is considered affected when the entries are mined with <br />the continuous miners. <br />Hydrologic analysis and information from the existing mine indicate that the undermining and consequent <br />subsidence would directly impact only the Wadge Coal unit. The Trout Creek Sandstone, located approximately <br />220 feet below the Wadge Coal Seam, is separated from the mined coal by low-permeable shales and will not be <br />impacted by the proposed mining operation. The Twenrymile Sandstone aquifer is located approximately 680 feet <br />above the Wadge Coal Seam, and is separated from the mined coal by at least 600 feet of low-permeable shales. <br />Under normal conditions, the Twenrymile Sandstone is not expected to be impacted by the proposed mining <br />operation. However, at [he Foidel Creek Mine, Twenrymile Sandstone monitoring well 006-82-48A, which was <br />completed in the Twenrymile Sandstone, was dewatered when the well casing collapsed after being undermined by <br />longwall operations. ]t appears the loss of water level was due to increasing the porosity of the sandstone <br />overlying and adjacent to the panel. The additional pore space would be filled, thus lowering the water level. <br />Also, [he area subsides and changes the relation of the surface to the prior measuring point. <br />During the development of the EMD to date (June 1999), only one zone of significant sustained inflow has been <br />encountered. While some faults encountered where cover was high (>600 feet) produced initial inflows estimated <br />~o be approximately 25 gpm, they had reduced to 5.5 gpm or less in under six months. However, beginning in July <br />1997, in the Southeast Submain stub area, particularly near No. 6 Entry Crosscut I, over 30 gpm was reportedly <br />produced. Measurements on December 2, ] 997 indicated that inflow to this area was less than 10 gpm. The water <br />had a conductivity of approximately 4,000 umhos/cm. In late November 1997, significant inflows were <br />encountered in the 6-Right Gateroad, primarily through the roof beginning after Crosscut 25 and continuing to <br />approximately Crosscut 27. These inflows also had a conductivity of approximately 4000 umhos/cm. The high <br />conductivity of this water indicates that it is derived from the Wadge Overburden near the spoils. All other <br />underlying units have a much lower conductivity. In the 1998 Mine ]nflow Study, the average conductivity of the <br />four sites sampled in the EMD (excluding the 6 Right inflow) was 2,380 µmhos/cm. <br />The areas of the high inflow, primarily in the 6-Right area, are on the limb of an anticline with dips to the North to <br />Northeast. No indication of faulting was observed in either area. The areas of highest inflow are also coincident <br />with the location of the Foidel Creek liniment. There is also relatively thin overburden (<400 to <600 feet) and is <br />less than 3000 feet from the subcrop of the Wadge overburden and the spoils. The Southeast Submain stub area <br />has a relatively shallow dip. The 6-Right Gateroad was driven in a direction of increasing dip. The area of highest <br />inflow (near Cross-Cut 26) is at the intersection of Foidel Creek lineament and an area of increasing dip. Both of <br />these geologic features can increase the fracturing of the rock, producing increased permeabilities. When the <br />liniment was penetrated farther downdip in Panel 7-Right, no significant inflows were encountered. The inflows <br />from 6 Right appear to be approaching a seasonally variable steady state condition. The monthly average inflows <br />ranged from 70 to 306 gpm in 1998 and 74 to 234 gpm in the first six months of 1999 (see Exhibit 49, Table E49- <br />2). <br /> <br />TR99-32 2.05-136 f1~~~~~Ln~9 F~L 0 6 2D00 1/03/00 <br />