2011-01-13_REVISION - C1981038 (8)

Home Browse Search

injected the Lower Coal Bearing member, particularly the B and C seams. These sills consist of diorite and appear to have their source to the northwest of Terror Creek. Hvdrologic Balance - Rules 2.04.5, 2.04.7, 2.05.3, 2.05.6(3), 4.05 Ground Water - Ground water information can be found on pages 27 to 41 of Section 2.04 and on pages 114 to 138 of Section 2.05.6 of Volume 1. Water quality documentation may be found in Volume 4 and is supplemented by annual hydrologic reports prepared since 1982. For a description of the ground water hydrology of the mine area and permit revision area and a discussion of the impacts of mining on ground water, please refer to the Hydrologic Balance portion and the Probable Hydrologic Consequences portion of Section B of this Document. Three categories of potential aquifers occur in the general area. These are alluvial and terrace deposits associated with the North Fork of the Gunnison River, the localized shallow alluvial/colluvial areas in the stream drainages, and ground water in the lenticular sandstones and the Rollins Sandstone of the Mesaverde Formation. The most significant occurrence of ground water in the general area is associated with the alluvium of the North Fork of the Gunnison River, located approximately two (2) miles southeast of the mine portals and 1,500 feet lower in elevation. Significant alluvial sand and gravel deposits averaging 34 feet thick exist along the North Fork from the mouth of Terror Creek to the confluence of the Gunnison River. There are numerous wells in the area which draw water from this alluvium; well yields range from 5 gpm to 120 gpm, with average yields of approximately 17 gpm (page 31 of Section 2.04.7, Volume 1). Steven's Gulch, an ephemeral stream located in the center of the permit area, drains an area of 6.0 square miles and contains several reaches of shallow alluvium/colluvium. Most of these reaches have little ground water except during periods of stream flow. The most significant area of alluvium/ colluvium occurs in the NW 1/4 of Section 13, Township 13 South, Range 92 West (Steven's Gulch wellfield), where a 25-foot-thick sandstone outcrop has created a topographic restriction such that a considerable thickness of alluvial sands and colluvial material have been deposited. Test wells drilled by the applicant indicate that the alluvium in this area can support a pumping rate of approximately 28 gpm (Ground Water Hydrology Appendix, Volume 4). The applicant had installed a production well and used this water for domestic use, dust control, and fire control. The recharge to the Steven's Gulch well field area is through flow from the adjacent colluvial deposits and from a leaky pipeline aqueduct. The ground water flows through the colluvium downslope to the alluvium, where it becomes trapped or temporarily stored. This situation is somewhat modified by the presence of landslide complexes which occur throughout the general area in the Bowie and five adjoining quadrangles (Colorado Geological Survey Information Series 5, 34p.). Ground water will tend to move down through the more permeable material and along lateral shears of these landslide complexes. The sources of ground water discharges from the Steven's Gulch alluvium at the well field are through the applicant's wells, through underflow within the alluvium down the old bedrock channel of Steven's Gulch, and through discharges to the stream during high water table conditions in spring and early summer. Water quality analysis for the Steven's Gulch well water indicates good quality water, with none of the parameters exceeding the recommended standards of the Colorado Department of Public Health and the Environment. 14