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tertiary butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tert-amyl methyl ether (TAME), tertiary butyl alcohol (TBA), and ethanol. The detection limits for benzene and vinyl chloride will be no greater than 0.5 micrograms per liter (ug/L). The detection limits for the other target VOCs will be 1 ug/L or less. If no VOCs are detected in any of the initial samples, additional samples (10-percent more) will be collected and analyzed for benzene and vinyl chloride with detection limits of no greater than 0.1 ug/L. A hand-held instrument with a proper detection limit (500 ppm, or less) will also be used to check for the presence of methane in the soil gas samples. Although not currently anticipated, should encountered site soils consist primarily of tight formations such as clay or silty clay, URS will make a recommendation to DTSC regarding whether soil gas sampling should proceed or whether the field crew should instead collect soil matrix samples for VOC analysis using the USEPA-approved method 5035 preparation technique. In such event, URS would proceed as directed by DTSC> During the installation of the soil gas probes, soil lithology will be characterized and sample intervals potentially adjusted should certain structures be found such as clayey soils that may inhibit flow of the volatile gases. Lithology will be recorded on boring logs by a field engineer or geologist working under the supervision of a qualified California-registered engineer or geologist. Soil matrix samples will be collected from the borings used to install the soil gas probes. Soil matrix samples will be collected from all locations at the surface (0-6 inches below ground surface [bgs]) and at 5 feet bgs. At the six locations in specific areas of concern, soil matrix samples will also be collected at 15 feet bgs. All soil samples will be analyzed for California Code of Regulations (CCR) Title 22 total metals, semi-volatile organic compounds (SVOCs) [including polycyclic aromatic hydrocarbons(PAHs)], organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and total petroleum hydrocarbons (TPHs). If VOCs are detected by the soil gas investigation, soil matrix samples will be collected from the corresponding locations and depths and will be analyzed for VOCs. To provide required data for the human health screening evaluation conducted as part of the PEA, two soil samples will be collected for physical parameters including soil moisture content, total porosity, bulk density, grain-size distribution, pH, total organic carbon (TOC), and effective permeability. One of these samples will be collected at the predominant interval of the soil gas samples at 5 feet bgs and one will be collected at 15 feet bgs or at the interval of a significant change in soil lithology within the first 15 feet bgs. In addition to the planned samples, if areas significantly stained with waste oil or other petroleum products or organic constituents are observed, URS will recommend to DTSC additional soil sampling, and will proceed as directed by DTSC. Recommended analyses for such samples would include SVOCs, TPH and lower detection limit analysis for polynuclear aromatic hydrocarbons (PAHs) by EPA method 8310. Recommended sampling intervals would likely be at 0 to 0.5-foot and 2 to 3 feet bgs. According to the Phase I ESA, groundwater occurred at a depth of about 110 feet bgs in the Site vicinity in spring 1999. No groundwater sampling is currently planned due to the depth to groundwater and the absence of any known localized source of groundwater contamination. Potential health risks to the school population due to possible volatilization from unknown deep subsurface sources will be screened using the soil gas survey. If a perched aquifer is encountered during the PEA investigation, groundwater samples will be collected using the Hydropunch sampling technique (or equivalent). These samples will be analyzed for Title 22 dissolved metals, VOCs, SVOCs (including PAHs), OCPs, PAHs, and TPHs. These analyses will provide screening-level groundwater data due to the method of collection and will provide support for the characterization of soil contamination. Accurate characterization of groundwater would require an Page 4 PAPEA Lockeford\Work Plan\Lockeford WP.doc