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P <br />Seneca II Technical Revision 47 (2009) Ground Water Points of Compliance <br />Points of Compliance - Bedrock <br />At Seneca II Mine, the Wolf Creek coal, Wadge coal, and Lennox coal were removed during mining. <br />As the replaced spoil material recharges, the groundwater can potentially affect the adjacent undisturbed <br />strata of the Wadge coal overburden and the Wadge coal. The Lennox coal was completely removed <br />during mining and thus, cannot be affected. <br />As can be seen in Tab 7, page 48, only one aquifer test was conducted on the Wadge coal, Well GW- <br />S 17, revealing a hydraulic conductivity of 1.52E-3 cm/s (4.3 ft/day). This value is relatively high, most <br />likely due to this well being located next to the final highwall. Fracturing of the coal seam may have <br />occurred during coal and overburden blasting. Other aquifer tests conducted in the area prior to mining <br />on the Wadge coal show lower hydraulic conductivities, ranging from 2.47E-7 cm/s at Yoast Mine to <br />1.06E-5 cm/s at Seneca II-W Mine. Aquifer tests of the Wadge coal overburden were conducted at <br />Seneca II-W Mine and Yoast Mine and ranged from 3.53E-7 cm/s to 1.76E-4 cm/s. Excluding the one <br />aquifer test conducted at Seneca II on the Wadge coal, the materials in this area show low hydraulic <br />conductivities. Groundwater flow velocity through the Wadge coal was estimated for the nearby Yoast <br />and Seneca II-W mines and ranged from 1.63 ft/yr to 14.71 ft/yr. <br />The low yields of these materials limit their widespread use. Wadge coal transmissivities ranged from <br />0.015 ft2/day at Yoast Mine to 0.36 ft2/day at Seneca II-W, again excluding those tests with suspect <br />construction. In the Wolf Creek coal, transmissivities ranged from 0.001 ft2/day at Seneca II-W to 0.328 <br />ft2/day at Yoast. The low yields are rated poor to infeasible for domestic water supply and are <br />insufficient for irrigation. <br />Other factors, including attenuation and dilution, should assist in limiting water quality impacts to a <br />close downgradient proximity. Dilution by unaffected groundwater plays an important role in reducing <br />dissolved ion concentrations. Attenuation also reduces dissolved ions and can occur through physical, <br />chemical, physiochemical, and biological mechanisms. Although, attenuation is difficult to quantify, <br />there are some site characteristics that suggest an increased rate of attenuation will occur. These include <br />fine grained silty and clayey soils, low permeability shales and siltstones in the overburden and adjacent <br />lithologies, neutral and alkaline groundwater conditions, and low rainfall and infiltration rates. <br />Downward seepage into the underlying strata is also unlikely. This is substantiated by a study <br />conducted by the USGS at the Seneca II Mine that found the hydraulic gradient of groundwater in the <br />bedrock is upward, evidenced by water levels in the coal seams above the land surface. This would <br />prevent the downward migration of mineralized spoil water to the bedrock groundwater. In fact, water <br />from the bedrock may seep into the spoil material above. The calculated water balance indicated that <br />discharge from the reclaimed spoil groundwater to the bedrock was only one percent of the total <br />discharge from the spoil material and was therefore negligible (USGS 1994). <br />• Aquifers of regional significance include the Trout Creek Sandstone and the Twentymile Sandstone. <br />These are thick beach deposit sandstones that can potentially be used for water supply. However, the <br />TR-47 7-3-1 Revised 1/09