GENERAL30618 - Laserfiche WebLink

Home Browse Search

-33- Use of these stations allows determination of approximate inflows to the North Fork of the Gunnison River contributed by the study watershed boundary located on Figure 1. The average monthly flows are illustrated on Table 2, along with the inflows to the North Fork of the Gunnison River from Minnesota Creek. These figures were used to determine the amount of outflow via the North Fork of the Gunnison River from the basin. Obviously, such predictions are not absolutely accurate. For example, less than 3 years of data existed for Minnesota Creek and 1 year (1977) experienced drought conditions. However, for purposes of this assessment, such figures provide a rough approximation of flows through the general area. PROBABLE HYDROLOGIC CONSEQUENCES Effects of the Bear Coal Company Mining Operation on Ground Water Faults and fractures intercepted during the Bear Mining operation could produce mine inflows as is the case in other mines in the North Fork Basin. Any inflows which may occur are expected to be minor, based on mining,of the C Seam in the Bear No. 1 and No. 2 and previous mining of the C Seam in the old Edwards mine, which has resulted in minor inflows. As of 1985, the Bear No. 3 Mine has not reported any inflows. Apparently, the massive sandstone which caps the lower coal member produces very little water. These mines have not discharged mine water, but have imported water into the mines for underground use. There is a possibility that water existing in the Rollins Sandstone or other sandstones below the C Seam could appear as mine inflows from the floor, through faults or fractures penetrating the lower strata, or produce floor heaving. Floor seeps have not been encountered in any of the three Bear mines. Floor seeps have occurred in other mines in the area. Mine inflows of 10 gpm have been reported, associated with the D Seam floor at the Orchard Valley mine, near Paonia. The only other bedrock aquifers in the general area, above the Bear mines, are the saturated lenticular sandstones in the Barren member above the F Seam. The C Seam is separated from the Barren member by over 300 feet of sedimentary strata. No impact on the hydrologic functions of the Barren member aquifers, including springs supplied by those aquifers is anticipated. Effects of mining on the alluvial aquifer of the North Fork of the Gunnison are expected to be insignificant, and are discussed in the Alluvial Ualley Floor Section (VII) of this document. Disturbance to the alluvium is limited to construction and operation of surface facilities and coal storage. No underground development waste will be stored on the surface. No coal processing waste will be produced. A portion of the water used in the Bear No. 3 mining operation comes from the alluvium of the North Fork. This causes only a localized draw down in the alluvial water table, since the alluvium has a high transmissivity, and the well is located in close proximity to the river. Thus, the Bear operation will have little if any impact on alluvial ground water use in the area.