2009-03-19_PERMIT FILE - C1980005

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Twentymile Sandstone is approximately 500 feet above the Wadge Coal seam. It was present at higher elevations on the permit area, but is not found in strata immediately adjacent to the Seneca II permit boundary. Therefore, the Twentymile Sandstone is not affected by the mining activity at Seneca II. The Trout Creek Sandstone of the Illes Formation lies approximately 300 to 400 feet below the Wadge Coal seam and approximately 60 to 100 feet below the Wolf Creek Coal seam. The Trout Creek sandstone is essentially under confined conditions and is separated from the surface mining by finer grained lithologies of the Williams Fork Formation, which are predominantly gray to black siltstones, limey shales, and silty, fine-grained sandstones. Because of the thickness and low permeability of the strata separating the Trout Creek Sandstone from the mining and the upward hydraulic head below the mined strata, it is unlikely that the mining could have any effect on the water quality of this unit. For these reasons, the current coal mining operations at Seneca II are unlikely to significantly impact bedrock groundwater offsite, and that no point of compliance is warranted for bedrock groundwater. Points of Compliance - Alluvial At Seneca II Mine, the flow direction of the reclaimed spoil will be predominantly towards the adjacent western drainage of Little Grassy Creek and Grassy Creek, which have potential to receive direct runoff and groundwater inflow from the mine operation (Figure 1). Aquifer tests conducted in the Grassy Creek alluvium at Yoast and Seneca II mines showed a range of hydraulic conductivities between 1.06E-5 cm/s and 4.23E-4 cm/s. The low yields associated with the alluvial materials will limit its use. • Nonetheless, the alluvial material has the highest hydraulic conductivity of the materials downgradient of the mine site and would be most indicative of any offsite impacts. Therefore, the well GW-S70-A (SGAL70) will be designated a compliance monitoring well. This well is actively being monitored and will be sufficient to capture any impact to Grassy Creek alluvial groundwater quality from the Seneca II Mine. Results from recent monitoring can be seen in Table 1. This table also provides the agriculture and domestic use groundwater standards from Regulation 41. Wells along Grassy Creek at the Seneca II Mine are analyzed for concentrations of groundwater compliance parameters. Table 2 provides a statistical summary of ambient water quality data for those wells. Likewise, wells in the Grassy Creek basin at the Yoast Mine, shown in Figure 2, were analyzed for ambient concentrations of these constituents. Table 3 provides a statistical summary of ambient water quality data for all Yoast Grassy Creek alluvial wells. The ambient cutoff date chosen was 1/31/94, as specified in Reg. 41. Maximum values observed in Tables 2 and 3 are also provided on Table 1. Outliers in Tables 2 and 3 were indentified and not used in Table 1. Ambient values were higher than the Reg. 41 standards for iron, lead, manganese and sulfates. These values are underlined on Table 1 and will serve as the standard for those parameters. For all other parameters, the more stringent of the Reg. 41 domestic or agricultural standards will serve as the standard. Those values are also underlined on Table 1. Review of Table 1 indicates that the water quality from well GW-S70-A has not exceeded any of the proposed standards from October 2005 to May 2008. Potential contributors to the mineralization of the alluvial water include the underlying Lewis Shale, • which is a marine shale with high concentrations of these constituents that underlies portions of the TR-47 7-3-2 Revised 1/09