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hT1 KLEINFELDER ,i 2 SITE SETTING 2.1 SITE LOCATION The Disco Site is located at the southeast corner of Filbert Avenue and Myrtle Streets in Stockton, California (see Plate 1). The address of the site is 110 Filbert Street, Stockton, California. The site is located in Section 6 (extrapolated), Subsection M, Township 1 North Range 7 East, Mount Diablo Base and Meridian. 2.2 GEOLOGY AND HYDROGEOLOGY The site lies within the Great Valley Geomorphic Province of California. The valley is approximately 400 miles long and averages about 50 miles wide, and comprises about 20,000 square miles. The valley has been filled with a thick sequence of marine and non-marine sediments from the late Jurassic to Holocene. The uppermost strata of the Great Valley represents, for the most part, the alluvial, flood, and delta plains of two major rivers (Sacramento and San Joaquin Rivers) and their tributaries. The valley deposits are derived from the Coast Ranges to the west and the Sierra Nevada to the east. Granitic and metamorphic rocks outcrop along the eastern and southeastern flanks of the valley. Marine sedimentary rocks outcrop along most of the western, southwestern, southern, and southeastern flanks; and volcanic rocks and deposits outcrop along the northeastern flanks of the valley. The valley geomorphology includes dissected uplands, low alluvial plains and fans, river flood plains and channels, and overflow lands and lake bottoms. . Site specific geologic information was obtained from a document prepared for Del Monte by CH2M Hill titled, "Additional CPT Investigation and Monitoring Well Installation Report, Del Monte Disco Property, Stockton, California" (dated March 2002), and past documents pertaining to the installation of other monitoring wells on the site. According to the CH2M Hill reports, the site is underlain by unconsolidated alluvial sediments. The soils encountered during subsurface investigations show clay, silt, sand, and gravel. The predominant soils are interbedded sandy clay and silty sand. The majority of the native sediments near the site consist of Miocene to Holocene continental rocks and deposits of a heterogeneous mixture of interbedded, generally poorly sorted clay, silt, sand and gravel. Water level information was also obtained from the CH2M Hill groundwater reports. Generally, during the period of the monitoring (1995 to date) the groundwater elevation'beneath the project site has been -20 feet in reference to mean sea level (msl). The direction of groundwater flow has been predominantly to the southeast. Historical groundwater information obtained by CH2M Hill indicates that in 1991 groundwater elevation beneath the site was approximately-53 feet msi l 12280.MON I ST02R519 Page 3 of 14 0 2002,Kleinfelder,Inc September 19,2002