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Page 5 <br />monitoring at TR-3 is 332.4, and for TR-4 is 281.6. TDS values at TR-3 were expected to rise <br />between 2000 and 3000 mg/1 due to mining of the Moffat area.3o <br />Probable Hydrologic Impacts <br />Bedrock Groundwater <br />In response to the Division 1994 Midterm Review of the permit, monitoring of a well into the <br />Trout Creek Sandstone, TCS-1, was initiated in 1995 to validate31 the prediction of no probable <br />hydrologic impacts to the Trout Creek Sandstone.32 Information in the 2004 Annual Hydrologic <br />Reports validates the prediction from 1995 through 200333 <br />The piezometric level is higher within the Trout Creek Sandstone than the elevation of springs at <br />the surface. These springs are at the unconfined water surface of the spoil groundwater at the <br />low-wall of the former mine pit. Further, there is approximately 200 feet of relatively <br />impermeable strata between the spoil groundwater of the former mine pits and the Trout Creek <br />Sandstone. The intrusion of spoil ground water into the Trout Creek Sandstone aquifer is <br />unlikely due to the head differential between the backfill groundwater and bedrock groundwater. <br />Backfill Groundwater <br />Backfill groundwater developed as a result of the mining method, and is not considered as <br />impacted by mining. Springs and seeps have developed near the crest of the lower coal mine pit <br />low wall, suggesting that backfill groundwater migrates down through the relatively permeable <br />backfill to a reservoir formed by the lower portion of the mine pit (intersection with the more <br />impermeable bedrock units left in place at the low-wall). Numerous springs are in evidence as a <br />result.34 Additional information that supports this hypothesis includes the levels of spoil ground <br />water in monitoring well WR-1 and the flows at Spring No. 1 (SP-1). <br />Spring No. 1 (SP-1) and groundwater monitoring well WR-1 and are in close proximity to each <br />other, WR-1 being in the spoil at an elevation above the low-wall location of SP-1. The elevation <br />of water at SP-1 (the ground surface) is 712835. The elevation of water in WR-1 varies slightly, <br />but remains around 715036. The elevation of spoil ground water is estimated to be about twenty- <br />two feet higher, at a distance of some 400 feet directly upslope from, the elevation of the spring. <br />Groundwater would migrate from the levels of WR-1 to the levels of Spring SP-l. <br />'0 PAP page 2.5-97 <br />" PAP page 4.6-147 <br />iz PAP page 2.5-47 <br />" 2004 AHR Appendix F <br />;" PAP, page 2.5-50 <br />35 AHR, 2004, page 27 <br />'b AHR, 2004, page 27 <br />