2010-12-17_REVISION - C1981019 (108)

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RULE 2 PERMITS The majority of the springs, with bedrock sources, appear to be contact springs. A contact spring results from the infiltration of water from the surface to a porous zone (such as sandstone) above a horizontal hydrologic barrier (such as shale) where the water preferentially flows along the contact to the exposure. This type of spring is common in areas where alternating sequences of lithologies exist that exhibit differential hydraulic conductivities, such as the Williams Fork Formation. Springs within Little Collom Gulch that will be eliminated by the mining operations include SPRLC -01, SPRLC -02, SPRLC -03, VI 1, and V29. Additionally, VI, V 10, and V32 (West Fork of Jubb Creek) may be impacted by mining activities via potential elimination of portions of their recharge areas. Additional springs in the Collom Gulch and Jubb Creek drainages are unlikely to be affected, due to their location upgradient /updip, cross -dip, or on the opposite side of an incised stream channel of the proposed mining. Table 2.05.6 -4 lists the springs and seeps found in the vicinity of the proposed mining areas. The locations of the investigated springs and seeps are presented on Map 1013. Data collected for the springs and seeps were previously summarized in Table 2.04.7 -49. Two springs (SPRLC -01 and SPRLC -02) maintained flow during July and August 2005 in Little Collom Gulch, and produced a total of 0.30 cfs during spring runoff in June 2005, and 0.045 cfs during August 2005 baseflow. Spring/seep SPRLC -03 only produced flow (0.009 cfs) in December 2004, and produced no measurable flow for any other sampling event. Springs /seeps V 11 and V29 produced no measurable flow for any sampling event. All Little Collom Gulch spring and seep flows subsequently infiltrated into the valley fill or were captured by stock ponds, because no flow was observed at streamflow monitoring point LLCG, which was dry throughout the 18 month sampling period. In the West Fork of Jubb Creek, the three springs potentially affected by mining operations (VI, V 10, and V32) produced a total of approximately 0.042 cfs in May 2006, and 0.024 cfs in September 2005. Potential Impacts to Bedrock Groundwater Quantity No impacts are anticipated to the quantity of groundwater in the Williams Fork Formation or the Trout Creek Sandstone of the Iles Formation. Drilling and monitoring by Colowyo in the permit revision area identified very limited perched water in the shallow coal beds and interburden, and saturated conditions downdip of the Collom Lite pit area in the sequence to be mined. Dewatering of the sequence to be mined in the Collom Lite pit will be necessary. However, the low permeability and depositional nature of the strata restrict the ability of the bedrock to store and transmit water, and there are no continuous non -coal beds in the Danforth Hills. Groundwater movement is mainly controlled by fractures of varying orientation. The Williams Fork Formation is not a significant water supply source in the Danforth Hills. It is not used as a source of water where the valley -fill aquifers and surface waters are accessible. Where wells yield water, the water quality in the Williams Fork Formation is generally good. Very few registered wells for domestic, agricultural, or industrial purposes are completed in the Williams Fork Formation in the vicinity of the Collom pits. Drilling by Colowyo and other parties encountered groundwater in the Collom Lite pit area in the litholgic sequence which is planned to mined, as discussed in Section 2.04:7. The water is present under both perched unconfined and confined conditions. The shallow, perched water - bearing units are of very limited extent due to removal from the valley areas by erosion. The deeper water - bearing coal seams are more laterally continuous, but few of the interburden units are laterally continuous. Maintaining a dry pit will, in some areas, require dewatering in advance of mining or pumping to remove groundwater that enters the pit. Collom — Rule 2, Page 127 Revision Date: 1/23/09 Revision No.: PR -03