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<br />CNAPTERTHREE <br />Atfectrd Environment ~ i <br />to intersect this unit. It is present throughout the central Piceance Creek Basin and in neazby <br />Horse Draw Mine, where it is 6 feet thick and averages 65 to 70 percent nahcolite by weight. <br />3.1.3.4 Salable Minerals <br />Limited amounts of salable minerals are available within the sodium lease tract:.. These include <br />sand, gravel, and sandstone. The sand and gravel aze found in Quaternary alluvial deposits, and <br />the sandstone is from the Tertiary Uinta Formation. This material is used for road construction <br />and maintenance in this azea of the basin. No known leases for sand and gravel or sandstone aze <br />found within American Soda's sodium lease tracts. <br />3.2 SOILS <br />The study azea for soils includes the mining well-field and initial processing plant azea known as <br />the Piceance Site, a 400-foot wide corridor along the pipeline route, and the final processing <br />plant area at the Pazachute facility. Soils are described in soil surveys conducteci by the USDA <br />Soil Conservation Service (SCS). The Soil Survey of Rifle Area Colorado (SC:i 1985), and Soil <br />Survey of Rio Blanco County Area, Colorado (SCS 1982) provide detailed information on the <br />physical and chemical characteristics of soils throughout the study area. Soil characteristics, <br />including erosion potential, and salvage and reclamation chazacteristics are sunnnarized below <br />for soil mapping units within the study azea. <br />3.2.1 Regional Soil Conditions <br />Soil conditions across the study area are highly variable due to differences in the soil-forming <br />factors of pazent material, topography, vegetation, and climate. The semi-arid environment of <br />the resource azea has affected soil development. Lack of moisture, cool nights, ~md infrequent <br />high temperatures suppress vegetation growth and slow the chemical and biological processes <br />needed for good soil development. In addition, geologic erosion has progressed too rapidly for <br />many soils to develop distinct deep horizons (BLM 1994). Soils in the Piceance Creek Basin <br />occupy varying landforms including drainageways and narrow valleys, rolling hills, and high <br />mountains with very steep sideslopes. Slopes range from 0 to 90 percent. Soils aze shallow to <br />deep, and have formed in alluvium, colluvium, residuum, and reworked eolian d~:posits derived <br />dominantly from shale and sandstone (SCS 1982). Native vegetation ranges from streambank <br />riparian shrub communities along perennial streams to sagebrush communities that occur at all <br />elevations, mountain shrub communities at higher elevations, and pinyon juniper communities <br />on shallow soils on mountainsides and ridges. Major uses include wildlife habitiu and livestock <br />grazing. <br />Soils aze considered fragile when they exhibit the following criteria: <br />• Areas rated as highly or severely erodible by wind or water, as described by the SCS. <br />• Areas with slopes greater than 35 percent if they have one of the following soil <br />chazacteristics: (a) surface texture that is sand, loamy sand, very fine sandy l~~am, fine sandy <br />loam, silty clay or clay, (b) a depth to bedrock that is less than 20 inches (described as <br />3-8 Geology <br />