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forest Luke October 6. 1998 Trapper Mininglnc. Page 6 Ground water- Suitability for intended post-mining uses 13. Uses and aquifers. The post-mining uses of ground water in the vicinity of Trapper will be domestic, irrigation, and livestock uses. Only the massive sandstone aquifers within the upper Williams Fork Formation at Trapper could reasonably be expected to yield enough high quality water to serve as a local supply source. These aquifers are the Twenty Mile sandstone, 2"d White sandstone, and 3`d White sandstone. Coal aquifers in the area possess neither the deliverability nor water quality to be considered for reliable water supplies. Twentymile Sandstone. The Twentymile Sandstone is the only regionally extensive aquifer in the vicinity of the Trapper Mine. It is several hundred feet deeper than the deepest mining at Trapper and has shown no effect from Trapper's mining. 2"d White Sandstone (well P-5) and 3'd White Sandstones (well P-8). The 2"d and 3'd White Sandstones overlie the stratigraphic sequence being mined at Trapper. The 3rd White has been cut by Trapper's pits; the 2"d White crops out down-slope from the pits. TDS concentrations in both of the White Sandstones have increased over the past several years in the two Trapper wells (P-5 and P-8) that monitor these aquifers in East Pyeatt Gulch (see Table 2, above). Suitability of water from wells P-5 and P-8. Prior to mining, high TDS levels caused electroconductivity values of water in both wells to exceed DMG's guidelines for irrigation water of 1.0 mmhos/cm. Water from both wells, though, remains suitable for the lower level use of livestock and wildlife watering based on compazison with water quality suitability standazds for domestic livestock issued by the State of Wyoming Department of Environmental Quality. (The Wyoming standards are used for comparison because Colorado has not issued suitability standazds specifically for livestock or wildlife.) Trapper believes the TDS (and electroconductivity) will eventually subside afrer mining and reclamation as discussed under Probable Hydrologic Consequences, Section 4.8.3 of the mining and reclamation permit. Comparison of 1997 hydrologic data with PHC section of permit 14. The need to update PHC. Trapper's expectations for the probable hydrologic consequences (PHC) of the mine aze set forth in Section 4.8.3 of the mining and reclamation permit. These consequences appear reasonable but need updating now as Trapper's pits approach the east end of the permit area. The revised PHC should be submitted as a Technical Revision that includes revisions of the following discussions: a) Impacts to the 2"d and 3rd White Sandstones. The revised discussion should include: 1) predictions of the impacts to each of the wells completed in those