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inflow studies and dewatering rates indicate that flows on the order of approximately 55 gpm resulted from mining
<br />activity in this area. Since the SMD has been sealed, measurements of inflows and discharge indicate that this rate
<br />has declined to 15 to 20 gpm. This inflow will be discussed further in the mine water-balance discussion below.
<br />These inflows can be used to estimate overall inflows to the mine for areas that aze not neaz the subcrop of the coal.
<br />Based upon the estimated inflow of 55 gpm and an affected mine area of 2,064 acres the estimated inflow per unit
<br />area is 0.027 gpm/acre. An area is considered affected when the entries are mined with 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 seam by low-permeable shales and will not
<br />be impacted by the proposed mining operation. The Twentymile Sandstone aquifer is located approximately 680
<br />feet above the Wadge Coal Seam, and is separated from the mined coal by at least 600 feet of low-permeability
<br />shales. Under normal conditions, the Twentymile Sandstone is not expected to be impacted by the proposed mining
<br />operations. However, Monitoring Well 006-82-48A, which was completed in the Twentymile Sandstone, was
<br />dewatered when the well casing collapsed after being undermined by longwall operations. It appears that loss of
<br />the well resulted from anomalous subsidence fracturing which intercepted the well bore.
<br />During development of the EMD to date (June 1999), only one zone of significant sustained inflow has been
<br />encountered. While some faults encountered in high cover areas (>600 feet) produced initial inflows estimated to
<br />be approximately 25 gpm, flows subsequently declined to 5.5 gpm or less in under six months. Beginning in July
<br />1997, however, in the Southeast Submain stub area, particulazly neaz No. 6 Entry Crosscut 1, over 30 gpm was
<br />reportedly produced. Measwements on December 2, 1997 indicated that inflow to this azea had declined to less
<br />than 10 gpm. The water had a conductivity of approximately 4,000 umhos/cm. In late November 1997, significant
<br />inflows were also encountered in the 6-Right gateroad, primarily through the roof beginning after Crosscut 25 and
<br />continuing to approximately Crosscut 27. These inflows also had a conductivity of approximately 4,000
<br />umhos/cm. The high conductivity of this water indicates that it is derived from the Wadge Overbwden near the old
<br />surface mine spoils. All other underlying units have a much lower conductivity. In the 1998 Mine Inflow Study,
<br />the average conductivity of the fow 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-
<br />Northeast. No indication of faulting was observed in either azea. The areas of highest inflow aze also coincident
<br />with the location of the Foidel Creek liniment. Limited overbwden thickness(<400 to <600 feet) and proximity
<br />(less than 3,000 feet) to the subcrop of the Wadge overbwden and the spoils, appear to be contributing factors. The
<br />Southeast Submain stub azea has a relatively shallow dip. The 6-Right gateroad was driven in. a direction of
<br />increasing dip. The azea of highest inflow (neaz Crosscut 26) is at the intersection of Foidel Creek lineament and an
<br />area of increasing dip. Both of these geologic featwes can increase the fracturing of the rock, producing increased
<br />permeabilities. When the liniment was penetrated farther downdip in Panel 7-Right, no significant inflows were
<br />encountered. The inflows from 6-Right appeaz to be approaching a seasonally variable steady state condition. The
<br />monthly average inflows ranged from 70 to 306 gpm in 1998 and 74 to 234 gpm in the first six months of 1999 (see
<br />Exhibit 51, Table E51-2).
<br />Future Inflow Estimates: Planned futwe mining will be in areas of high cover, most of which aze greater than
<br />1,000 feet, with limited areas with 700 - 1,000 feet of cover. None of the planned futwe mining will be in areas of
<br />steep dip, and should not encounter major structwal features. All futwe mining areas will be more than 3,000 feet
<br />from the coal seam subcrop. Therefore, it is not anticipated that any new significant sustained flows will be
<br />encountered, and inflows are expected to be the same or lower than those measwed per unit area in other parts of
<br />the mine. Since the average cover in the NMD and WMD will be greater than 1,000 feet, lower unit inflows aze
<br />anticipated. Using the inflow mte of 0.027 gpm/feet developed for the SMD, anticipated inflows to the EMD
<br />(excluding 6-Right) were projected to increase to 85 gpm due to the additional 400 acres to be affected, plus 65
<br />gpm from the 6-Right inflow, for a total of 150 gpm. These estimates were compared with measwed mine
<br />discharges and water balance calculations and a good match was found. Approximately 6,500 total acres had been
<br />mined by the end of 2002 (includes 2,050 acres -SMD, 2,850 acres -EMD, and 1,600 acres - NMD). For the
<br />2002 inflow study, flows included 20 gpm from the Northeast Mains, 55 gpm from the SMD, 85 gpm from the
<br />EMD, measurements of 25 gpm from the NW-Mains raisebore, and 65 gpm from 6-Right (subsequently declined to
<br />about 10 gpm), for a total of 250 gpm.
<br />TR07-59 2.05-136 04/02/07
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