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West Elk Mine '. West Elk Mine Experience WWE's evaluation of the probable hydrologic consequences draws heavily on information obtained from current and previous mining of the B and F-Seams, respectively, at the West Elk Mine. As described previously in the Subsidence Survey section, WWE (working closely with Messrs. Rold and Dunrud) has determined that previous experience regazding subsidence and hydrologic consequences for the current permit azea, applies to the Box Canyon permit revision azea as well. This continues to be the case despite the B East Mains fault inflows in 1996 and the January 1997 14SE (a.k.a. 1 SE) Headgate inflows. A large database of hydrologic information, for both water quality and quantity, has been collected for springs, groundwater, and surface water at the West Elk Mine. ~ These data have been collected since 1977 and aze contained within this permit document, associated permit revision or renewal application "Adequacy Responses," Quarterly Hydrology Reports (1977 to 1987), and Annual Hydrology Reports (1982 to present). In general, the mining experience at the West Elk Mine to date indicates the following features of the hydrologic system and changes resulting from mining: • Typcially, groundwater occurrence in the Upper arid Lower Coal Members of the Mesaverde Formation has been the result of the downward percolation of snowmelt and precipitation through the stratified siltstones, sandstones, shales, and coal. The . primary permeability of the bedrock units is very low (approximately 1x10 cm/sec) ~ and recharge to the Mesaverde Formation is primarily through joints and other fractures in the bedrock. Noted exceptions are the inflows of groundwater from the lazge fault systems in the B East Mains and iri the 14SE Headgate. These unprecedented inflows represent the fast significant (> 100 gpm) groundwater inflows to the mine from a fault system or other source. Faults or fracture systems with similar displacement have been encountered elsewhere in the mine, but have had little or no groundwater yield. The bedrock units within the Upper and Lower Coal Members of the Mesaverde Formation aze not aquifers. The Cumulative Hydrologic Impact Assessment -North Fork of the Gunnison River (CHIA, CDMG 1992) describes the Mesaverde Formation as "a poor aquifer composed of incompetent shales and sandstones in which water storage is restricted to (localized) buried channels". Most groundwater dischazge from the system is from springs exiting the steep outcrop faces formed by incised drainages such as Box Canyon, North Fork, and Sylvester Gulch or from colluvium generally in association with landslides. Springs typically occur on the south or west sides of drainages on the down-dip outcrop exposures. Spring flows aze typically less than 10 gpm with annual dischazge peaks in the spring which generally diminish to no flow in the fall. I. • Mining of the B and F-Seams to date has shown little groundwater inflow, except for the two fault system inflows as noted above. The average rate of inflow between 1.05-139 November 2004 PR/!