Laserfiche WebLink
<br />!. Quantitative Impac7s of Mining <br />shafrs, and 100 gpm came from a fault. WWL's projection comes within 20% of accurately <br />predicting inflows associated with non-fault inflows. <br />Greystone re-examined the original data, recent water level data and information acquired from <br />drilling to prepare a more accurate estimate of inflows (Table 3A). Greystone assumes that the <br />Maxwell, Blue and Red coal seams are the predominant sources of water, with minor <br />contributions from channel sands with localized areal extent. WWL assumed that 225 feet of <br />overburden above the coal was saturated based on water level data acquired from well LA-221. <br />This value was considered the effective thickness of the leaking overburden. Examination of <br />representative drill hole data acquired since 1980 suggests that the water level can vary from <br />195.4' to 484.2' above the top of the Maxwell Coal (Table 3B), and in fact the original logging <br />of holes 218-and 221 in 1976, prior to installation of casing, found a height of water table above <br />the top of the coal of 303.7' and 321.9' respectively. Consequently, the same drawdown <br />analysis was performed using a range of saturated thicknesses. <br />Coal seam transmissivity values from the WWL Report ranged from 0.56 [0 1.92 ft2/day, with <br />an average coal transmissivity of 1.27 ft2/day. These established the three cases (I, II, and III). <br />Coal permeability was set at 2.1 x 10-4 ft/day. The effective saturated thickness of the leaking <br />overburden aquifer was set at 195.4 ft for Case A, and 484.3 ft for Case B. The leakance <br />• values ranged from 722 ft to 2098 ft with discharge to the mine per foot of perimeter ranged <br />from 0.152 to 0.443 ft2/day (Table 4). These results were then applied to the perimeter and <br />areal extent of the mine (Table 5) to determine mine inflow from the face and roof respectively. <br />Three scenarios were examined: the existing configuration of the Golden Eagle Mine, the <br />configuration for the current permit term, and the life-of-mine configuration. Case II inflow <br />predictions utilizing the maximum coal transmissivity of 1.27 ft2/day appeared to best represent <br />the situation currently observed at the mine (Table 6). <br />• <br />Currently the mine is producing 0.14 gpm/acre of mine. Figure 5 is a diagram of seepage rates <br />by acres of mined coal over time. This curve corresponds well with the seepage rates antici- <br />pated in the 1980 study, and, due to the homogeneity of stratigraphy, structural geology, <br />topography, and climate, may represent a good way to project future inflows based on total acres <br />mined. Figure 6 is a graph of inflows from shafts and holes by acres of mined coal. The slight <br />decline in gpm/acre might represent an offset from dewatering of perched water tables at old <br />sites to additional inflow from newer sites. <br />There will continue to be a constant inflow of 80 to 100 gpm associated with the SE-1 TG fault. <br />The mine is currently using the discharge for underground dust suppression activities. Should <br />the mine encounter another fault of comparable magnitude, inflows will increase beyond the <br />current projection. The station for measuring the flow from the fault was relocated, and now <br />9 <br />