2012-09-06_REVISION - M2008070 (21)

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will have a beneficial effect to RBC by providing employment and income to at least four households in RBC, and given the mortgage crisis and severe downturn in real estate sales over the past year, four steadily- employed individuals will also be a positive effect on the RBC housing market, albeit a small one in the regional context. Since the WRC pit location is ideally located to provide materials for the planned upgrades to RBCR 5, the pit will be a benefit by reducing wear and tear on Hwy 64 and reducing county expenditures for haul costs for materials during the upgrade process. 3.10 GEOLOGY /SOIL DATA /GEOLOGICAL HAZARDS Affected Environment: The proposed WRC pit is located in the northeast portion of the Colorado Plateau physiographic province (Howard and Williams 1972). The area is characterized by large, south - facing escarpments formed by gently sloping sedimentary rock. Topography in the vicinity is fairly moderate along the White River, giving way to more rugged terrain with steep, deeply incised tributary drainages. Bedrock geology at the site is mapped as the Uinta and Green River Formations (Hail and Smith 1994). Alluvial terrace deposits are common along both Piceance Creek and the White River. Geological hazards in the area include seismicity and ground subsidence. There have been faults mapped in bedrock outcrops well south of the WRC site, though none of them have identified as active of potentially active (Duncan 1976, USGS 2007). There has been little earthquake activity mapped in the area. The WRC site lies in a location where ground motion would be less than 18% of the acceleration of gravity from a maximum probable earthquake with an occurrence probability of 2% in 50 years (USGS 2009). Ground subsidence in Colorado usually occurs due to solution of evaporate rocks, collapsible soils and locations over mined -out areas (Colorado Geological Survey 2001). None of these conditions are present at the WRC location and there has been no documented subsidence in the project area. Soils in the area include 7 types, but by far the vast majority in the Phase 2 site are Patent Loams, 3 -6 percent slope. Patent loams are deep, well- drained soils on terraces and fans. They are formed from alluvium or colluvium derived from sandstone. The upper 10 inches are generally loam, which changes by varying degrees from clay -loam to very fine sandy loam from 10 -60 inches below ground surface. Permeability is high, effective rooting depth is 60 inches or more and available water capacity is high. Erosion capacity is moderate. Environmental Consequences of Proposed Action: The WRC pit should not affect geology in the area as it will be a shallow surface mine in alluvial deposit. It will not increase potential for seismicity or ground subsidence in any way. Soils will be temporarily affected by stripping and stockpiling until mining operations are completed. The plan of operation for the Phase 2 site calls for a phased approach wherein only about 20 -30 acres of the site will be disturbed at once, with mining operations beginning on the west end and working operations toward the east. Environmental Solutions, Inc. Page 26 of 30 March 09