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14 Soil Survey Nearly Level Soils in Basins and on Basin Rims Pescadero soils have a slope of 0 to 2 percent. The soils in this group are in low positbns on the Typically, the surface layer is moderately fine textured. landscape, primarily in the central part of the county. The-subsoil is fine textured, and the underlying materia Elevation ranges from about 5 feet below sea level near Is Moderately fine textured. The soils are calcareous Thornton to 200 feet above sea level near Farmington. and saline-sodic throughout. The shrink-swell pote 'al Levees have been cotlskucted in some areas to control is ham. A high water table is regulated at a dell f 3 floodwater. They should be periodically checked and a to 6 feet by drainage systems. The soils are Proper maintenance program should be developed- rare flooding. )ect to Drainage ditches and pumps are needed to maintain Minor in this unit are the Capay, Me ' and Vemalk the water table below the rooting depth of crops. The soils. These soils are not calcareous aline-sodic average annual precipitation is 10 to 14 inches, and the throughout- Capay soils are in the . er interfan average annual air temperature is 60 degrees F_ The basins. Memft silts are on the r flood plains. average frost-free period is 250 to 300 days. Vemalis soils are on the high Iluvial fans. These soils are deep or moderately deep to a Areas of this unit are mainly as irrigated cemented hardpan or are very deep. They are poorly cropland. A few areas used for horresite drained to moderately well drained_ Depth to the high development. The in - soils generally are suited to water table is commonly more than 5-0 feet but ranges 'irrigated crops, but are poorly suited to most from 1-5 to 5.0 feet in some areas_ The soils in basins perennial, deep r ed crops. Limitations include saline have a moderately fine textured or fine textured surface sodic cond epth to the high water table, and ver layer and a high shrink-swell Potential_ The soils on slow pe Intensive management is required to basin rims have a moderately coarse textured or reduce sal and maintain productivity. moderately fine textured surface layer and commonly Whe unit is used for homesite development, have a hardpan. the in ' itations are very slow permeability, a high These soils are used mainly for irrigated crops or shrin I Potential, low strength, depth to the high pasture. A few areas are used for homesite by table, and saline-sodic conditions. The main development. is rare flooding. Onsite sewage disposal is Three map units are in this group_ They make up because of the very slow permeability and the about 18 percent of the survey area. high water table and may cause contamination of the ground water_ Structural damage can result from the 5. Willows-Pescadero high shrink-swell potential and low strength. These limitations should be considered when foundations, Poorly drained moderately fine textured and fine buildings, and roads are designed_ The plants selected textured. saline-sodic sods that are very deep have been partially drained in basins for landscaping should be those that are adapted saline-sodic conditions. Dikes and channels that have This map unit is in basins in the lout ern part of outlets for floodwater can protect buildings from the county. It is in two long and nano eas south of flooding. the San Joaquin River. The soils fo in alluvium derived from mixed or sedimenta ock sources. Q0.7wh. one Hollenbeck-Stockton Levees have been constructed control floodwater from the San Joaquin River. o, drainage systems poorly drained and moderately well drained, have been installed. fine textured soils that are moderately deep and deep to This unit makes up 1 percent of the survey a cemented hardpan and that have been drained in area. It is about 61 pe nt Willows and similar soils, 20 some areas, on basin rims and in basins percent Pescadero similar soils, and 19 percent This map unit is in basins and on basin rims in the components of m' extent. central part of the county. The soils formed in alluvium Willows soils ve a slope of 0 to 2 percent. derived from mixed rock sources. Levees have been Typically, the rface layer and underlying material are - constructed in some areas to control floodwater. They fine textur a soils are calcareous and saline-sodic are used in conjunction with drainage ditches to reduce througho a shrink-swell potential is high. A high wetness. water to is at a depth of 4 to 6 feet. It is regulated by This unit makes up about 13 percent of the survey drainage systems in some areas. The soils are subject area. it is about 46 percent Jacktone and similar soils, to rare flooding. 21 percent Hollenbeck and similar soils, 20 percent