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-23- There are a total of 13 decreed water rights on or near the lease area but outside the five year permit area. 'Ihe applicant has determined that an additional 29 downstream rights might be affected by the life of mine project. However, since the impacts will be addressed in future permit terms, no additional analysis is needed for this permit decision. The majority of springs that might be impaired are located above the "F" seam outcrop. The Mt. Gunnison No. 1 Mine is an underground mine within the F coal seam. Mining is to ultimately progress from the portals in the valley of the North Fork of the Gunnison River up the dip of the F seam under the watershed of Minnesota Creek. The extraction of coal will be by continuous mining methods. Controlled subsidence will occur during pillaring. Development waste rock and processing waste from the Mt. Gunnison mine will be disposed of in one permanent disposal pile. One pile, the Upper Waste Pile, has been approved but not yet constructed. Another pile, the Lower Waste Pile, has been proposed for approval in this document. Load out facilities for the Mt. Gunnison Mine are located along the North Fork of the Gunnison River. Regional Geology The Somerset Coal Field lies on the southeast margin of the Piceance Basin, and just south of Grand Mesa. The sedimentary strata exposed in the Somerset Coal Field dip at 3 to 5 degrees to the north and northeast. Only minor faulting of limited vertical displacement has been observed in the existing Blue Ribbon, Bear, and Hawk's Nest Mines. However, in the Orchard Valley Mine, a fault with a displacement of 50 feet was encountered during mining. Drill hole data indicates the presence of other faults in the life-of-mine area with similar displacements. One major fault has been encountered in the Somerset Mine. The faults which have been encountered in existing mines tend to be high angle normal faults. The steep slopes of the stream valleys and the instability of the rock strata in the North Fork Drainage Basin has contributed to numerous landslides, mud flows and rock falls. These mass wasting features have been mapped by W.R. Junge of the Colorado Geological Survey and published as an open file report, entitled "Geologic Hazards, North Fork Gunnison River Valley, Delta and Gunnison Counties, Colorado". Geologic units exposed in the North Fork Drainage Basin consist of Late Cretaceous to Early Tertiary Age sedimentary strata, Tertiary Age igneous intrusives, and Quaternary Age alluvial and colluvial deposits. A generalized stratigraphic column of Late Cretaceous units can be found in Figure 3. The units are described below in ascending order.