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West Elk Mine <br />Three of the five entries experienced inflows during construction while the remaining two were <br />dry. Entry No. 4 experienced the greatest inflow (approximately 5 gpm). Within one week this <br />flow had diminished to less than 1 gpm. Entry No. 1 produced a small quantity of water from <br />the bottom of the coal at a rate of less than 1 gpm, which dried up within two weeks. The <br />sandstone roof of the entry was dry. Entry No. 5 produced drips, perhaps as much as 0.1 gpm for <br />about one week. <br />It is uncertain how much water levels in the low permeability strata aoound the portal have been <br />affected. However, certain conclusions can be drawn. First, it is cleaz that a uniform cone of <br />depression has not occurred. While it is likely that water levels in the low permeability <br />colluvium around the mine entry may have declined as a result of construction and de-watering, <br />water levels have reached a new equilibrium condition. Water levels in the inclinometers <br />changed little since September 1982. Similarly, the water level in monitoring well SOM-13 has <br />remained relatively constant during this same period, (See Map 34 for the location of well SOM- <br />13). <br />This experience neaz the F Seam subcrop indicates that the colluvium, coal, and bedrock aze <br />recharged locally. Limonite stains in sandstone above the F Seam coal neaz the outcrop also <br />suggests local recharge of water. However, the experience at West Elk Mine indicates that <br />sandstone roof rock above the F Seam coal is usually dry. The small quantity of water produced <br />from the F Seam coal itself and in the colluvial overburden during construction of the portals in <br />the wettest part of the yeaz were the first indication that mine inflows would not be substantial as <br />mining progressed. Soon after completion of the entries in 1982, mine inflows virtually ceased, <br />but typically reappeaz at low rates during snowmelt runoff each season. <br />Based upon these observations, WWE has concluded that the current and past mining has not <br />materially impacted the groundwater contained within the colluviaVlandslide deposits in the <br />vicinity of the mine portal. <br />Direct Miniup Impacts <br />Direct mining impacts on groundwater include the effects of longwall mining subsidence and <br />induced mine inflows from saturated channel sandstones above or from damaged fault <br />zones in saturated sandstone layers beneath the mined interval. A general discussion of each <br />is followed by a more detailed presentation of the impacts from mining the F, E, and B Seams. <br />Subsidence Effects <br />The most direct mining impact to groundwater is from overburden subsidence resulting from <br />longwall coal extraction. Subsidence is simplistically defined as the downward displacement of <br />strata overlying the mine workings under the influence of gravity. For purposes of chazacterizing <br />subsidence effects, the four subsidence zones, as discussed eazlier in Section 2.05.6, are again <br />described as follows (see Figure 1, Exhibit 60): (1) Caved zone, (2) Fractured zone, (3) <br />Continuous deformation zone, and (4) Neaz-surface zone. <br />• <br />2.05-147 Revised Jwre 1005 PRIG; Rev. March 2006; Rev. May 1006 PRl0 <br />