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San Joaquin County, California 125 Egbert, Guard, and Rioblancho soils in the slightly lower soil for septic tank absorption fields. Properly designing positions. Also included are small areas of Stockton buildings and roads can offset the limited ability of the —soils that are highly calcareous or saline-sodic soil to support a load. Houses, roads, and streets throughout. Included areas make up about 15 percent should be constructed above expected flood levels. of the total acreage. This map unit is in capability units IIs-5 (MLRA-17), — Permeability is slow in the Stockton soil. Available irrigated, and IVs-5 (MLRA-17), nonirrigated. It is in water capacity is moderate. The shrink-swell potential is vegetative soil group C. high. The effective rooting depth is limited by the hardpan at a depth of 40 to 60 inches. Depth to the 251—Stockton-Urban land complex, 0 to 2 percent 'water table is more than 5 feet, but water may be briefly slopes. This nearly level map unit is in basins. perched above the hardpan after periods of heavy Elevation is 10 to 40 feet. The average annual rainfall or irrigation. Runoff is slow, and the hazard of precipitation is about 14 inches, the average annual air —water erosion is slight. The rate of water intake in temperature is about 60 degrees F, and the average irrigated areas is 0.1 inch per hour. The soil is subject frost-free period is about 270 days. to rare flooding, which occurs during years of This unit is 50 percent Stockton clay and 35 percent —abnormally high precipitation. Urban land. The components of this unit occur as areas Most areas are used for irrigated crops or orchards. so intricately intermingled that it was not practical to A few areas are used as irrigated pasture or for urban map them separately at the scale used. development. This unit may provide wetland functions Included in this unit are small areas of Galt soils in and values. These should be considered in plans for landscape positions similar to those of the Stockton soil enhancement of wildlife habitat or land use conversion. and Egbert and Ryde soils in the slightly lower This unit is suited to irrigated row, field, and orchard positions. Also included are small areas of soils that --crops. The main limitations are the slow permeability have been altered by construction activities and and depth to the hardpan. Because of the restricted Stockton soils that have moderately coarse textured or permeability, water applications should be regulated so moderately fine textured overwash or that have a ,that the water does not stand on the surface and hardpan at a depth of 30 to 40 inches as a result of damage the crops. The hardpan limits the suitability for leveling. Included areas make up about 15 percent of deep-rooted crops. Where feasible, deep ripping of this the total acreage. restrictive layer can help to overcome this limitation. The Stockton soil is deep to a hardpan and is —The soil should be cultivated only within a narrow range somewhat poorly drained. It formed in alluvium derived Of moisture content. It is too sticky when wet and too from mixed rock sources. Mottles in the profile indicate hard when dry. Furrow, border, and sprinkler irrigation a somewhat poorly drained soil; however, drainage has ,systems are suitable. Returning crop residue to the soil been improved by levees and reclamation projects. or regularly adding other organic material improves Typically, the surface layer is dark gray clay about 29 fertility, minimizes crusting, and increases the rate of inches thick. The upper 8 inches of the subsoil also is water intake. dark gray clay. The next 5 inches is mixed light This unit is suited to irrigated pasture. Irrigation water brownish gray and grayish brown clay loam. The lower can be applied by sprinkler and border methods. part to a depth of 60 inches is a variegated dark grayish Leveling helps to ensure a uniform application of water. brown and dark brown, weakly cemented to strongly Proper stocking rates, pasture rotation, and restricted cemented hardpan. In some areas the surface layer is grazing during wet periods help to keep the pasture in silty clay, silty clay loam, or clay loam. good condition and protect the soil from compaction. Permeability is slow in the Stockton soil. Available If this unit is used for urban development, the main water capacity is moderate. The shrink-swell potential is 'limitations are the high shrink-swell potential, the slow high. The effective rooting depth is limited by the The eability, depth to the hardpan, and low strength. hardpan at a depth of 40 to 60 inches. Depth to the rare flooding is a hazard. Properly designing water table is more than 5 feet, but water may be briefly —fOUndations and footings and diverting runoff away from perched above the hardpan after periods of heavy buOdmgs help to prevent the structural damage caused rainfall or irrigation. Runoff is slow, and the hazard of bYShrinking and swelling. On sites for septic tank water erosion is slight. The rate of water intake in a. fPtion fields, the slowermeabilit be p Y can irrigated areas is 0.1 inch per hour. The soil is subject - e by increasing the size of the absorption field, to rare flooding, which occurs during years of Ing the trench with sandy material, and installing abnormally high precipitation. rption lines. Ripping the hardpan improves Urban land consists of areas covered by roads, _1itY and thus also improves the suitability of the driveways, sidewalks, parking lots, buildings, and other t