2008-03-03_PERMIT FILE - C2006085 (16)

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Ms. Angela Bellantoni Apri125, 2007 Page 6 are no wells completed within the projected rubble zone, accordingly, water level impacts will not directly occur to wells as a result of fracturing within the rubble zone. Although unlikely, it is possible that ground water flow could be altered in the ediments overlying the coal seam as a result of fractures in the rubble zone. Ground water flow in overlying sediments in the same stratigraphic interval as the rubble zone could be altered due to changes in ground water flow in the rubble zone. In order to determine the potential for water level changes in wells completed in the same stratigraphic interval as the rubble zone, we used the Theim equation and the following hydraulic properties of the sediments to determine the distance to zero water level drawdown from the angle of draw. Hydraulic conductivity: 0.1 gpd/ft2 Starting head (ft above rubble zone): 200 ft Estimated inflow: 30 gpm Radius of mining operations: 3000 ft Unconfined conditions, steady state conditions r: ~ ~,~11s Note that hydraulic conductivity value is supported by specific capacity data from wells and published reports (Horizontal Hydraulic Conductivity Estimates for Intact Coal Barriers Between Closed Underground Mines, Environmental and Engineering Geoscience; August, 2006; v. 12; no. 3; P. 272 -282). ~~ 7 rv c~-S,~ -~'",5~ This analysis indicated that projected water level drawdowns are not expected to extend more than 1,000 feet beyond the angle of draw within the interval 100 feet above the coal. There are no wells completed within the 1000-foot drawdown radius within the _~ stratigraphic interval of the rubble zone. Accordingly, impacts to wells as a result of fracturing from subsidence are not expected. ~,~ ~~ Expected Water Quality Changes Nine residential wells were identified in stratigraphic intervals above the projected rubble z eno and within the 1,000-foot drawdown zone, as presented in Appendix 5. As stated above, water level changes are not expected in these wells because they are not completed in the same stratigraphic interval as either the mine or the rubble zone, but because of the remote possibility of impacts to these wells due to fracturing of the formations above the rubble zone, we recommen t at t ese nine wells are included in t e~i well monitoring program. Mining operations will not introduce contaminants to the ground water system; therefore water quality changes are not anticipated. Most nearby wells, including the Chandler Heights wells, are located up gradient of the mine (see Figure 6 in our March, 2006 hydrology report), and therefore water quality impacts to nearby wells including the Chandler Heights wells is nearly impossible. /k/.. . .~~ ~/~ •