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A deeply buried fault, the Stockton-Tracy Fault, <br /> is inferred to exist to the southwest of the <br /> site on an axis between Stockton and Tracy. <br /> However, this fault is not known to have caused <br /> any earthquakes in historic times. The most <br /> probable cause of seismic hazards are the <br /> Calaveras-San Andreas-Hayward Fault system to <br /> the west, and the Bear Mountain-Melones Fault <br /> system to the east. Both contain known active <br /> faults which have caused earthquakes in historic <br /> times. The Council of Governments Seismic Safety <br /> Element published in 1973 estimates a maximum <br /> probable earthquake of 8.3 on the Richter Scale <br /> for this area. All of the State of California <br /> is in earthquake zone 3 under the Uniform <br /> Building Code. This is the most severe standard. <br /> 2. Soils (See Map Insert - page 22) <br /> Project area soils are Stockton Adobe Clay, <br /> Capay Clay and Wyman Clay Loam. The first two <br /> soils predominate. They are both heavy clay <br /> soils characterized by imperfect drainage in <br /> the surface and subsurface layers, with strong <br /> profile development (stratification) , deriving <br /> from mixed but mainly basic igneous material. <br /> The predominance of fine size particles causes <br /> high shrink swell behavior when dried or wetted <br /> and requires careful agricultural management. <br /> They are best utilized for the production of <br /> vegetable and grain crops. <br /> Clay soils are less suitable than sandy or <br /> gravelly soils for roads and foundations and <br /> sometimes requires more sub-base material. <br /> To the north of the existing channel of Mosher <br /> Slough there is a trace of a former stream <br /> course. In this trace is an area of Wyman Clay <br /> Loam. This soil is better drained and is suita- <br /> ble for tree crops. However, because of the <br /> small extent and irregular shape of this area <br /> no differentiation in cultivation has occurred. <br /> Local topography is quite flat. There is a slight <br /> slope of about .2% to the wests Mosher Slough <br /> which is leveed and about 10' in depth. <br /> 3. Hydrol24y <br /> Mosher Creek is the only remaining waterway tra- <br /> versing this property. At one time as the 1915 <br /> topographic map shows there was a stream roughly <br /> parallel and about 1000' north of Mosher, although <br /> the trace of this creek shows up in the aerial <br /> -5- <br />