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• r • Mr. Brian Tay] -' Formatted:Rl9ht - <br /> uaorta 1l 2008 _ I <br /> �- __-- DeMted:Mc Brien Teylor9 <br /> - •---- oeleted:ia,�aryai.2oosy <br /> A summary of previous work performed at the site and additional background information is presented in <br /> Attachment A. - <br /> PRODUCT RELEASES AND SOURCE AREAS <br /> Table I in Attachment B lists the product releases reported at the facility. Based on these releases and the <br /> historic soil and groundwater analytical data,there appear to be three source areas(SAs)beneath the site <br /> (Pacific Environmental Group,Remedial Action Plan,March 23, 1994): <br /> • SA-1 is located near Tank 14 and the former rail car off-loading area. The primary source is - <br /> probably Tank I4. Wells MW-10,MW-11,and MW-16 monitor groundwater within this area. <br /> • SA-2 is located near the truck loading rack. The primary source is probably the product <br /> distribution rack. Well MWA and MW-24 monitor groundwater within this area. <br /> • SA-3 is located near wells MW-2 and MW-13R. The primary source is probably the former <br /> unlined holding pond located west of the office building. <br /> The three SAs are marked on Fig 1. <br /> SITE GEOLOGY AND HYDROGEOLOGY <br /> Site Geology <br /> The sediments underlying the site are comprised of the Great Valley sedimentary sequence. Near-surface <br /> sediments are characterized as unconsolidated to semi-consolidated,mostly nonmarine; alluvium,lake, <br /> playa,and terrace deposits that are Quaternary in age(CDMG, 1977). <br /> I <br /> Site investigation activities characterize soils beneath the site as primarily fine-grained silt and clay soils <br /> - that average approximately 18 feet in thickness. Coarser-gained(sandy)soils have been observed,but to <br /> a lesser extent. Silty fine-gained sands were encountered to depths of approximately 2 feet below grade - <br /> (fbg) at well MW-17, and to approximately 17 fbg at MW-9. Please note: The 'coarser" sediments <br /> consist of fine-grained sand and silty sand,with minor clay lenses and some interbedded gravel. With the <br /> exception of well MW-9,these coarser grained soils are unsaturated(occur within the vadose zone)and <br /> overlie silt/clay horizons. -Saturated coarse-grained soils were encountered in the southern portion of the <br /> site, at depths below 20 tbg in wells MW-23,MW-25, MW-26, MW-27, DW-1, and DW-2. Geologic <br /> cross sections prepared by previous consultants are presented in Attachment B. Based on these cross <br /> sections,it does not appear that the saturated coarse-grained layers are laterally continuous. <br /> 241729 2 <br />