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• the Seneca 11-W production well (completed in the Trout Creek sandstone) indicates that <br />some degree of leakage occurs from the overlying confining layer. <br />Hydrologic Boundaries. Constant and semiconstant discharge boundaries occur where <br />aquifers crop out downg ra dient from recharge areas. There are no faults or unconformiti es <br />within the permit area which could restrict the lateral movement of ground water (Bass et. <br />al., 1955; Stewart, 1983). Aquifer testing did not reveal the presence of hydrologic <br />boundaries, although the aquifer tests conducted within the leasehold (primarily bailer <br />and sl ug-i njection techniques) stress a relatively small portion of the aquifer and are <br />unlikely to disclose barriers to ground water flow. The variable nature of the strata <br />suggests that minor lithologic boundaries may be present due to pi nch-outs, degree of <br />cementation, degree of fracturing, etc. <br />Infiltration and Permeability of the Unsaturated Zone. The unsaturated zone, also known <br />as the vadose zone, is that area above the water table where fluid pressure is less than <br />atmospheric. The unsaturated zone consists of unconsolidated material (soils) as well as <br />bedrock located above the water table. Infiltration (the process through which water <br />penetrates the surface) and permeability of the unsaturated zone will be examined below. <br />The majority of the unsaturated zone at Seneca II-W is composed of soil. Forty-four soil <br />units have been mapped on the leasehold at a scale of 1:4800 (1 inch = 400 feet). Most of <br />the soils are Borollic Vertic Cam6orthids, Li thic Cryoboralls, and Pachic Cryoboralls, <br />typical soils found in the cold, semi-arid regions of the western United States. Although <br />particle sizes vary, soils are generally 18 to 40 percent sand, 25 to 55 percent silt, and <br />20 to 60 percent clay. Detailed soil descriptions and maps can be found in Tab 9 of this <br />permit application. <br />Infiltration and permeability rates can be estimated through studies of soil physical <br />properties (structure, composition, porosity, cracking, etc.) Table 7-5 shows estimated <br />infiltration and permeability rates based on soil physical properties for Seneca II-W <br />soils. Infiltration rates range from slow (0.05 to 0.20 inches per hour) to moderately <br /> rapid (0.80 to 5.00 inches per hour), with most soils classified as moderate. <br /> Permeability rates range from very slow (less than 0.05 inches per hour) to moderately <br /> rapid (2.50 to 5.00 inches per hour). Most soils have a moderate to moderately rapid <br />• permeability rate, although a significant number of soils are classified as very slow. <br /> Infiltration and permeability rates were determined using USDA Soil Conservation Service <br />literature (USDA Soil Survey Staff, 1951; USDA-SCS, 1981a; USDA-SCS, 19816). <br />27 <br />