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H 4.5 Geology and Seismicity KRC-Aggregate's (KRC) sand and gravel deposit is situated in i the gently rolling foot hills of the Sierra Nevada Mountains, which are located east of the Property. West of the Property lies the Great Central Valley of California, a major agricultural producing region. In this area are flat-lying continental sedi- ments which dip slightly to the west and overlie steeply dipping metamorphic rocks. No known earthquake faults exist on or near the site. Exploratory borings encountered the Turlock Lake Formation r and the Laguna Formation. The Turlock Lake Formation is Pleisto- cene Age arkosic alluvium consisting of mostly fine sand, silt, and clay, with some pebbles of granitic and metamorphic rock. The Turlock Lake Formation is typically reddish brown in color + and contains a high percentage (20% to 40%) of silt and clay. It was generally encountered in the upper 5 to 10 feet of the bor- ings located east of Cord Road. ~ r The g Laguna Formation is Pliocene Age arkosic glacial meltwa- ter ter alluvium consisting of sand, silt, and gravel of quartz and metamorphic rock. The Laguna Formation is stratigraphically located beneath the Turlock Lake Formation. KRC's sand and gravel deposits are included in the Laguna Formation. Underlying the Laguna is the Tertiary-age Mehrten Formation. The Mehrten Formation consists of well-rounded andesitic conglomerate, , sand- stone, siltstone and claystone of nonmarine typically fluvial : origins. The units are stratified, but discontinuous over large t areas, with cut and fill channeling. Mudflow deposits derived from the Sierra Nevada occur as interbeds. The principal source of the Laguna Formation sediments is _ eroded metamorphic rocks. They are thought to have been derived from metamorphics in the Sierra Nevada Mountains to the east by glacial erosion and washed to their present location by glacial FS melt water. Pebbles and cobbles of the Laguna Formation are highly siliceous metamorphic quartzite which are extremely tough and very durable. Finer fractions of the Laguna Formation: in- clude sand, silt and clays. 4, 6 Soils The soils of the project site have been identified by use of Soil Conservation Service surveys for San Joaquin County. Thir- teen soil map units are found in the project area. Two of these ' units - gravel pit and tailings dump - are the result of anthro- pomorphic development activities. Of the remainder, units such f, as the Pentz cobbly sandy loam and Kaseberg fine sandy loam will be nominally disturbed, if at all. At the other end of the spectrum, the Montpellier - Cometa complex, Redding gravelly loam, and units of the Pardee soil series encompass the majority of the area where aggregate will be mined. A description of some of the characteristics of the soil map units in the project area appears in Table 4 . 6. 1. KRC Aggregate, Inc. ' Fill - 4 - April 1, 1994