2011-01-13_REVISION - C1981038 (8)

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annual temperature is 49.ONF at Paonia, with an average monthly mean of 24.5NF in January and 71.9NF in July. At Paonia, the annual precipitation is 8 to 15 inches. The local climate of the North Fork area is strongly influenced by microclimatic features - slope aspect, elevation, soil type, soil moisture content and vegetation. The steepness of the terrain, together with the type and amount of vegetation, orientation and range of elevation, are the major controls of the diurnal wind patterns. The shape and orientation of the North Fork valley is such that the drainage (or katabatic) flow is the dominant flow for most hours of the day. Prevailing winds are from the south-southeast, with wind speeds of ten (10) miles per hour occurring in June. Below Paonia, the wind speed appears to decrease sharply as the air spreads over the lower valley. Because of this strong drainage wind, frost pockets are not allowed to form, thus creating a favorable microclimate for fruit tree farming. Geology - Rules 2.04.5 and 2.04.6(2) Information on local and regional geology can be found on pages 15 to 26 of Section 2.04.6 of Volume 1. Maps 2-1, 2-2, 2-7, 2-8, 2-11, 2-12 and 6A-8 identify pertinent geologic features. Waste rock geochemical analyses can be found in Volume 6A. BRL has mined the D seam of the Upper Coal member of the Mesaverde Formation. The seam ranges in thickness from 2 to 21 feet in the permit area, with one split ranging in thickness from 15 1/2 feet to several inches. The coal dips 4N to 7N to the northeast. Two high-angle, normal fault zones are found in the area with displacement ranging between 1 and 50 feet (Map 2-8). The earliest fault system trends N65NE and dips 70N to 80N with displacements of 2 to 6 feet. The other fault system trends N35NW and dip 70N to 80N to the northeast. The geology is further modified in the northeast comer of Lease C-37210 where coked coal gives evidence of igneous activity associated with the Miocene Iron Point pluton. 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 3N to 5N to the north and northeast, and range in age from late Cretaceous to early Tertiary. Coal is produced from the Mesaverde Formation, a 2500-foot-thick sequence of sandstone, shale and coals overlain by the Ohio Creek conglomerate and underlain by the Mancos Shale (Figure 2). The Mesaverde Formation is composed of four members, which are, in order of decreasing age, the Rollins Sandstone, the Lower and Upper Coal members and the Barren member. Minor faulting of limited vertical displacement has been observed in other nearby mines. However, in the Bowie No. 1 Mine, a fault with a displacement of fifty (50) feet was encountered during mining, and drill-hole data indicates the presence of other faults in the life-of-mine area with similar displacements. The faults which have been encountered in these 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 have 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. The units of the Late Cretaceous in the general area are described below in ascending order. A stratigraphic column representing the geology of the coal member of the Mesaverde Formation in the permit area can be found on Map 2-10, Volume 2, and is found in this document as Figure 3. 12