2014-05-20_REVISION - C1982056 - Laserfiche WebLink

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With the additional geologic information obtained from the ongoing drilling, Map 23d has been updated to show the Wolf Creek interburden thickness. ➢ All drilling to date has not encountered any significant groundwater below the Wadge Coal Seam, as evidence by the lack of increases in return flows during the drilling operations. ➢ The lithologic sequence does not include any significant clay layers immediately above or immediately below the Wolf Creek Coal Seam. 2. Per Rule 2.04.7(1)(a)(i), (ii), (iii), (v), and Rule 2.04.7(b) no discussion concerning the any aquifers related to the Wadge /Wolf Creek interburden, the Wolf Creek coal seam, or, if potentially impacted, strata directly below the Wolf Creek coal seam has been provided. The Division has studied the Williams Fork Formation here and at other nearby mines and has made findings in the past regarding the need for baseline groundwater information below the Wolf Creek Coal which is the lowest coal seam to be mined with this proposed mine plan area. The Division has determined that there is no potential to impact the Trout Creek Sandstone which is the significant aquifer that underlies the Wolf Creek Coal. The Trout Creek Sandstone is a confined aquifer under potentiometric head. The confining shale layers above the Trout Creek Sandstone should prevent any integration of water from the overlying Wolf Creek Coal seam. The Foidel Creek PAP also discusses the hydraulic isolation of the Trout Creek Sandstone. Additional baseline data collection will be necessary to identify potential groundwater impacts below the Wadge Coal Seam and within the Wolf Creek Coal seam. Characterization of the quantity and quality of water within each aquifer /saturated zone above and within the Wolf Creek Seam is required. Please provide a plan for review that addresses baseline characterization of the Wadge CoaUWolf Creek Coal Interburden and the Wolf Creek Coal Seam. The plan, description, and associated maps should include both up gradient and down gradient monitoring wells and the Hydrologic Monitoring Plan and Probable Hydrologic Consequences portions of the permit document updated accordingly. Response: TC has worked closely with the Division to identify and develop reasonable baseline hydrologic information to adequately characterize the groundwater hydrologic system. Plans and relevant information have been incorporated in the expanded description of baseline surface and groundwater conditions in Sections 2.04.5 and 2.04.7, and the revised PHC discussion in Section 2.05.6(3) of the PAP which accompany these responses. In framing the hydrologic baseline and impact discussions, the following considerations are important (as further detailed in the referenced PAP discussions): ➢ The Wolf Creek Reserve area underlies areas of the Wadge Coal Seam which have been previously mined, consequently, any mining - related impacts on the Wadge Seam and associated overburden units have already occurred, as characterized and discussed in the current relevant PAP sections. Exploration drilling of the Wolf Creek Seam and associated units (Wadge /Wolf Creek Interburden, and immediate underlying units) has not encountered any significant amounts of groundwater, as evidenced by the lack of any significant increase in normal return flows during drilling operations. As noted in the Division's comments, the potential for the plamied development and future mining activities in the Wolf Creek Seam to impact the Trout Creek Sandstone, as an important regional aquifer, are negligible, given the distance of the Trout Creek Sandstone below the