2008-12-11_REPORT - C1981010 - Laserfiche WebLink

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Requirement Regulation Require- ment complied with ? (yes / no) Comment Potential aquifers. The post-mining uses of ground water in the permit area will be 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 3rd 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 based on monitoring data from well GF-1 (and previously GD-1(2)). 2"d White Sandstone (well P-5) and 3rd White Sandstones (well P-8). The 2"d and 3rd White Sandstones overlie the U. Prevention of stratigraphic sequence being mined at Trapper. The 3rd impacts to White has been cut by Trapper's pits; the 2nd White crops out ground water CDRMS down-slope from the pits. TDS concentrations in both of the that adversely regulations White Sandstones have increased over the past several years impact the 4.05.1(2) and yes in the two Trapper wells (P-5 and P-8) that monitor these postmining land 4.05.11 aquifers in East Pyeatt Gulch. use within the permit area Suitability for postmining use 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 comparison with water quality suitability standards 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 standards specifically for livestock or wildlife.) Trapper believes the TDS (and electroconductivity) will eventually subside, possibly hundreds of years after mining and reclamation, as discussed under Probable Hydrologic Consequences, Section 4.8.3 of the mining and reclamation permit. The suitability of Trapper's ground water for livestock and wildlife is expected to continue into the future based on long-term trends in Trapper's water quality data. Page 6