Laserfiche WebLink
Geologt a[reduu"/#X- Page 5 <br /> Site Conceptual Model Report(2006 Revision) <br /> Valentine(Castle Motors) <br /> Project No 723 2 <br /> June 16,2006 <br /> 1 <br /> The February 2006 CPT boring's groundwater and soil data are included in Table 2 in <br /> Appendix B <br /> 2.3 Chemicals of Concern <br /> ' The investigation of the release documented in Sections 2 1 and 2 2 above has identified <br /> gasoline range petroleum hydrocarbons as the chemicals of concern (COC) at the site The <br /> ' analysis of gasoline components is usually limited to benzene, toluene, xylene and ethyl <br /> benzene (BTXE), total petroleum hydrocarbons as gasoline (TPH-G), and oxygenated fuel <br /> compounds because (1) they are readily adaptable to gas chromatographic detection, (2) they <br /> ' pose a serious threat to human health (benzene is carcinogen), (3) they have the potential to <br /> move through soil and contaminate groundwater, (4) their vapors are highly flammable and <br /> explosive (Leaking Underground Fuel Tank Field Manual, State of California Leaking <br /> ' Underground Fuel Tank Task Force, October 1989), (5) a high percent of gasoline is <br /> composed of these compounds, and (6) because of the highly soluble nature of the <br /> oxygenated fuel compounds These COC have been identified at the site and are included in <br /> the monitoring and analytical protocols <br /> GTI has compiled fact sheets available on government and commercial internet sites for the <br /> COC and has included the sheets in Appendix D The fact sheets include physical and <br /> chemical properties of the COC in a pure form, not necessarily that which occurs upon <br /> release to the environment Although the solubility of the COC in water varies from <br /> chemical to chemical, each of the COC has the potential to migrate off site with groundwater <br /> movement <br /> ' 2.4 Geological/Hydrogeologic Site Characteristics <br /> Geolog <br /> ' The site is in southeast portion the City of Stockton, California, which is located in the San <br /> Joaquin Valley The Valley is underlain by a series of Quaternary and Tertiary marine and <br /> non-marine sediments The sediments investigated in the project are Pleistocene and <br /> Holocene non-marine sediments consisting of basin deposits major stream flood-deposits in <br /> basins lying between natural levees and alluvial fans (source Geologic Map of California, <br /> San Jose Sheet, Division of Mines and Geology, 1966) <br /> The following section discusses the subjective field observations and geology documented <br /> ' during this investigation based on the interpretations of various field geologists <br /> ' • SB-1 In boring SB-1, W J Hunter & Associates (WJH) described the soils as <br /> predominantly clayey from 5 to 10 feet below grade surface Sands were noted from 15 to <br /> 25 feet below grade and WJH indicated that the sands are probably fill material related to <br /> ' the former USTs The soils at 30 feet were characterized as mottled clay <br />