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' Ripona Market October 28,2004 Corrective Action Plan SITE CONDITIONS 2.0 H dro Bolo is Characteristics Y g � 2.1 Beneficial Uses of Surface and Groundwater Beneficial uses of the surface and groundwater in the Central Valley are Municipal, Domestic, and Agricultural Domestic use of the groundwater is through municipal and private water supply wells The area is extensively farmed with row crops and orchards irrigated by imported surface water Agricultural uses of the groundwater are limited to supplementing imported surface water for irrigation 2.2 Physical and Topographic Features The Ripona Market is located adjacent to state highway 99 in the town of Ripon, California Ripon is located in southernmost San Joaquin County on the eastern flank of the Central Valley The Stanislaus River, a t ibutary to the San Joaquin River, is located approximately 0 7 miles to the east The topography is subdued except for incised river channels and flood plains, Figure 1 10 23 Site Geology & Groundwater Occurrence The site is underlain by interbedded fine to medium grained distal facies sediments of the Pleistocene Modesto Formation The Modesto Formation in the Ripon area was deposited in the distal portion of coalescing alluvial fans derived from the Sierra Nevada Mountains to the east In the distal portions of the fans, sandy sediments interfinger with silts and clays deposited at the interface of the lacustrine environment, which was found in the center of the San Joaquin Basin The upper unit at the site, which is described below, represents a basinward transgression of the coarser grained alluvial fan sediments over the underlying finer grained lacustrine sediments A generalized hydrogeologlc cross section is shown in figure 3 The upper 15 feet of sediments explored at the site consist of medium dense to dense, fine to medium, angular, arkosic sands A fine-grained unit is present from depths 21 to 30135 ft This unit consists of interbedded predominately moderately consolidated low plasticity, clays, silts, and poorly sorted silty sands The consolidated nature of the fine-grained unit provided a solid foundation for the installation of the conductor casing Shallow unconfined groundwater was present at an approximate depth of 25 feet The basal portion of the borings below the fine-grained unit is composed of fine p g gT' p Ito medium grained moderately sorted unconsolidated sands The sands are 6 I