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Coal Methane Drainage Projee! - PaneG 76-74 Wett E!k Mine • Pave 3-7 3.0 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES This chapter briefly describes the affected environment for each of the resource or subject categories identified in Section 2.2.1 as "Issues Considered"; describes the environmental consequences for each of the project alternatives identified and described in Section 2.3; briefly discusses relevant considerations for other resource categories; and describes project considerations relative to short- term use versus long-term productivity. For each resource or subject category, the evaluation of environmental consequences addresses potential direct and indirect project impacts and cumulative impacts. Direct and indirect project impacts are evaluated for the project area of approximately 4,730 acres, as shown on Map Ml, Project Area Activities With Surface Stipulations. The area of cumulative impacts varies by resource or subject. Cumulative impact assessment areas are identified for each resource or subject in the following sections. 3.1 GEOLOGY, SURFACE WATER, GROUND WATER, AND RIPARIAN For geology, surface water, ground water, and riparian resources the project impact area is the project area. The cumulative impact area for geology is also the project area. The cumulative impact azea for surface and ground water includes the surface watersheds and ground water basins associated with Sylvester Gulch, Box Canyon, Wallow Road, Deep Creek, and the Upper ephemeral tributaries to the Dry Fork of Minnesota Creek. For riparian resources, the cumulative impact area is the project azea. 3.1.1 Affected Environment 3.1,1.1 Geology The bedrock geology in the project vicinity consists of interbedded sandstones, shales and claystones of the Upper Cretaceous Mesa Verde and Tertiary Wasatch Formations. The Mesa Verde formation is exposed in most of the drainages in the area. The Wasatch formation occurs as a thin veneer'of sandstones, shales, and claystones on the tops of mesas and ridges. Structurally, the bedrock dips at a low angle of 3 to 4 degrees to the northeast. There aze numerous faults in the azea, but fault displacements are minimal and the faults are not readily discernable on the surface, except where exposed in drainages and road cuts. The prevalent landform in the project area is aflat-topped mesa known as West Flatiron Mesa. The highest elevation of this mesa is just under 8,600 feet amsl. This mesa and adjacent ridges aze separated by indsed drainages that cut through the less resistant shales and claystones. Soils on the tops of mesas and ridgelines aze poorly developed and relatively thin. Soils on drainage side slopes and bottoms are developed on alluvium or slopewash colluvium derived primarily from the overlying Wasatch Formation. Soils range in texture from silty to sandy loams. The subsurface coal seams in this area occur in the Mesa Verde Formation. The proposed MDWs would vent methane from the Somerset (B) coalbed of the lower coal member of the Mesa Verde Formation. Geologic mapping indicates that the drill pads and MDWs on the West Flatiron Mesa above Panels 21 through 24 would be developed in the Wasatch Formation and the remaining drill pads and MDWs would be developed in the Mesa Verde Formation. 3.1.1.2 Geologic Hazards Geologic hazazds are present in the project azea in the form of current and historic rock falls, landslides, and slumps assoaated with unstable moderate to steep slopes. Areas of instability aze typically associated with steep slopes and saturated soil conditions. Slope aspect relative to geologic structure also affects stability, where dipping structure daylights on exposed slopes. Much of the project azea contains moderate (40 to 60 percent) and steep (greater than 60 percent) slope areas. Environmental Arrerrment ®.PD/MvrJ.WG/E.,/O.yM1 f/~/0}F/ VJFI /S/OSA