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III. Environmental Setting, Impacts, and Mitigations J. Geology, Soils and Seismicity years of abnormally high precipitation. Included in this mapping in unit are small areas of Archerdale soils and small areas of Jacktone soils that have moderately coarse textured overwash. Both of these soil are on the slightly higher parts of the landscape. Stockton Clay,0 to 2 Percent Slopes The Stockton clay is immediately adjacent to the existing landfill,on both the north and south sides,including the area of the existing borrow pit. This somewhat poorly drained,nearly level soil is in basins and formed in alluvium derived from mixed rock sources. It is deep to a hardpan. Mottles in the profile indicate a somewhat poorly drained soil;however,drainage has been improved by levees and reclamation projects. A few areas are dissected by intermittent sloughs that have been filled as a result of land leveling. Typically the soils profile has about 37 inches of clay over five inches of clay and clay loam. A weakly to strongly cemented hardpan extends to a depth of 60 inches. Permeability is slow and shrink-swell potential is high. The depth to the water table is more than 5 feet,but water may be briefly perched above the hardpan after heavy rainfall or irrigation. The soil is subject to rare flooding,in years of abnormally high precipitation. Included in this unit are small areas of Archerdale and Vignolo soils on the slightly higher parts of the landscape; Galt and Jacktone soils in landscape positions similar to those of the Stockton soil; and Egbert,Guard, and Rioblancho soils in the slightly lower positions. Soil Agricultural Resource The USDA Soil Conservation Service Land Use Capability Classification shows the general suitability of soils for most kinds of field crops. The Jacktone clay is suited to irrigated row, field,orchard,and vineyard crops. The main limitation are the slow permeability and depth to hardpan. The capability classification is IIIc-8 irrigated,and IVs-8 non-irrigated. Because of jrestricted permeability,water applications should be regulated. The hardpan limits the suitability for deep-rooted crops, and where feasible,deep ripping of the layer can help to overcome this limitation. The Stockton clay is suited to irrigated row,field, and orchard crops. The main limitations are the slow permeability and depth to hardpan. Because of the restricted permeability,water applications should be regulated. The hardpan limits the suitability for deep- rooted crops, and where feasible,deep ripping of this layer can help to overcome this limitation. This map unit is in capability units IIs-5,irrigated and IVs-5,non-irrigated. IH.J.3