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cam- Asa !- H.KLEINFELDER&ASSOCIATES i 5 DISCIISSION EE t= 5.1 REGIONAL GEOLOGY The Teichert site is located within San Joaquin County which is geomorphically part of beth the Great Central Valley and the Coast Range providences of California. Characteristic of Great Valley sediments, the site is underlain by a sequence of strata consisting of continental and marine gravels, sand, silts and clays. The valley was formed by the filling of a broad structural trough by erosional debris which originated i_ x from the surrowiding Coast Range :and Sierra Nevada providences. These �a deposits have been accumulating over the last 15 million years from the early part of the Fre-Cretaceous period to recent periods. Recent deposits consist of alluvial fan and stream channel deposits. The 4 alluvial deposits are generally derived from the the Coast Ranges and r consist of a heterogeneous mixture of gravels, sand, silt and clay. The stream channel deposits are typically considered to be more permeable than . the alluvial depodits and generally consist of sand and gravel with lesser i amounts of clay and silt. s� 5.2 SITE GEOLOGY Material encountered' during drf.11ing consisted of silt, clay, sand and combinations of these sediments. A surface soil of silty clay is underlain by clayey silt which in torr: is underlain.,by silty clay, sandy silt-silty sand aid finally silt. Two geologic cross sections prepared � c from the boring log data are presented as Pl,'tes 51 and 52. The contacts between soil types are generally gradational, both laterally and .' horizontally. The soil units,, are consijered to be. lensoidal and not laterally extensive or continuous, as would be expected from an alluvial depositional environment. Site soil permeabilities are relatively low, -- ----- ej --- ranging from l.5— -10 7.---to-2:O'-x-10-5--1'ermeabilities-of--the-various— -- ,--------- --.-- - Z, soils are presented previously on Table 5. 38-87-43 EM12 ,: