Laserfiche WebLink
• The unsaturated zone consists of unconsolidated materiel (soils) es well es bedrock <br /> Loca ted above the water table. Infiltration (the process through which water penetrates <br /> the surficial materiels) will be inferred below by examining the permeability of mapped <br /> soil textures within the Yoast permit area. <br />Permeability is a char ecteristie of soil which relates to the movement of water through <br />the profile. Criteria used to characterize soil permeability are based on the rate et <br />which water moves through the most slowly permeable layer to a depth of 60 inchec in e <br />saturated soil profile. <br />A majority of the surficial materials within the Toast permit boundary are unsaturated. <br />Twenty-eight soil units have been mapped on varying slopes on the leasehold at a scale of <br />1:4800 (1 inch 400 feet). Most ere typical soils found in the cold, semi-arid regions <br />of the western United States. Although the texture clessif icetions of soils mapped et <br />Yoast vary, they can be generalized for both the predominantly clayey soils end the fine <br />sandy soils. Typical textures for the clayey soils (gins o, Aabe rg, etc.) range from 5 to <br />20 percent sand, 25 to 35 percent silt, end 45 to 70 pe reent clay. The sandier soils <br />• (Coutis end Vinevada foams, etc.) exhibit textures ranging from 70 to 30 percent clay, 35 <br />to 50 percent silt, and 25 to 45 percent send. Detailed sail descriptions end maps can be <br />found in Tab 9. <br />Permeability rates can be estimated through studies of soil physical properties <br />(structure, composition, porosity, cracking, etc.). ieble 7-8 shows estimated <br />permeability rates for Yoast soils based on soil physical properties. <br />Permeability rates range from very slow (<,06 inches per hour) to moderate (0.6 to 2.0 <br />inches per hour). Almost 40 percent of the soils mapped within the Toast area may exhibit <br />very slow permeabilities (see Tab 9, Soils Resources). More then half of the mapped soil <br />units were classified as having permeability rates greeter then 0.2 minutes per inch, with <br />almost 30 percent exhibiting permeability rates approaching 2.0 inches per hour. <br />Permeability rates were determined using USDA Soil Conservation Service literature (USDA <br />Soil Survey Staff, 1951; USDA-SC S, 1981e; USDA-SCS, 198th). <br /> Although the hydrologic properties (permee bi liti es) of near-surface unsaturated bedrock <br />• strata within the Toast permit area are unknown in the absence of fracturing, the tightly <br /> cemented sandstones end shales underlying the area likely inhibit the vertical movement of <br /> infiltrating surface water. Field observations of exposed bedrock suggest that secondary <br /> 25 <br />