SU0004350 SSNL - Laserfiche WebLink

Home Browse Search

F, to the hardpan, and low strength. The rare flooding is a hazard. Properly designing foundations and footings and diverting runoff away from buildings help to prevent the r! structural damage caused to rare flooding, which occurs duringof b shrinking years y g and swelling. On sites for septic tank absorption fields, the slow permeability can be overcome by increasing the size of the absorption field. Ripping the hardpan improves permeability and thus also improves the suitability of the soil for septic tank absorption fields. Properly designing buildings and roads can offset the limited ability of the soil to support a load. Houses, roads, and streets should be constructed above expected flood levels. This map unit is in capability units Ills-8 (MLRA-17), irrigated, and IVs-8 (MLRA-17), nonirrigated. It is in vegetative soil group G. r193-Madera sandy loam, 0 to 2 percent slopes This moderately well drained neary level soil is on low terraces It is moderately deep to a hardpan It formed in alluvium derived from granitic rock sources In areas that have not been leveled, slopes • are complex and the landscape is characterized by hummocky microrelief. The native vegetation is mainly annual grasses and forbs. Meandering drainageways and closed depressions fill with water Fto form vernal pools during the winter in many areas. Elevation is 60 to 150 feet. The average annual precipitation is about 14 inches, the average annual air temperature is about 61 degrees F, Fand the average frost-free period is about 275 days. Typically, the surface layer is grayish brown and brown Y g Y sandy loam about 19 inches thick. The upper 4 inches of the subsoil is brown sandy clay loam. The next 6 inches is a claypan of light Freddish brown clay. The lower part to a depth of 60 inches is a pale brown and brown, indurated, iron- and silica- cemented hardpan. In some areas the surface layer is fine sandy loam or loam. Included in this unit are small areas of Alamo soils in drainageways, Exeter and Jahant soils in Flandscape positions similar to those of the Madera .soil, and Veritas soils on the slightly higher parts of the landscape. Also included are small areas of Madera soils that have slopes of 2 to 5 percent and areas where depth to the hardpan is as little as 10 inches and most of the soil has been removed, altered, or exposed as a result of deep leveling cuts. Included areas make up abobt 15 percent of the total acreage. Permeability is very slow in the Madera soil. Available water capacity is low. The shrink-swell potential is high. The effective rooting depth is limited by the hardpan at a depth of 20 to 40 inches. Roots are restricted to cracks and the faces of peds in the claypan, which is at a depth of 10 to 25 F inches. Water is briefly perched above the claypan and hardpan after periods of heavy rainfall or irrigation. Runoff is ponded in the small vernal pools, is very slow.or ponded in the leveled areas, and is slow on the convex slopes. The hazard of water erosion is slight. The rate of water intake in ' irrigated areas is 1.5 Inches per hour. The soil is not subject to flooding. Most areas are used for livestock grazing or for irrigated pasture, irrigated crops, or vineyards. A ` few areas are used for homesite development. This unit may provide wetland functions and values. These should be considered in plans for enhancement of wildlife habitat or land use conversion. F1I Where this unit is used for.livestock grazing, general management considerations in saturated soil conditions in concave areas following rainy periods. The characteristic plant community is mainly soft chess, foxtail fescue, and filaree. Grazing should be delayed until the soil , is firm enough to withstand trampling by livestock and the more desirable forage plants have had an opportunity to set seed.