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CONESTOGA-ROVERS <br /> &ASSOCIATES <br /> Ambient air samples will be collected adjacent to the vapor wells during sampling activities. The <br /> ambient air samples will be stored in Summa canisters. <br /> The vapor and ambient air samples will be labeled, entered onto a chain-of-custody record, and <br /> transported to a State of California certified laboratory for analysis. <br /> Written documentation of all field activities, conditions, and sampling processes, including names of <br /> field personnel, dates and times, etc. is important to obtain. Documentation includes weather conditions <br /> (temperature, barometric pressure, wind direction, and speed, humidity); surface conditions (presence of <br /> standing water and/or non-vegetative cover); and groundwater elevation measurements in monitoring <br /> wells adjacent to the soil gas probes. <br /> Chemical Analyses: Vapor and ambient air samples will be analyzed for total petroleum hydrocarbons as <br /> gasoline (TPHg), total petroleum hydrocarbons (middle distillates), benzene, toluene, ethylbenzene, <br /> xylenes (BTEX), methyl tertiary butyl ether (MTBE), tertiary butyl alcohol (TBA), naphthalene, and <br /> isopropyl alcohol by an appropriate analytical method (e.g., TO-15, TO-3) as determined by the <br /> laboratory. In addition, fixed gases (i.e.,02, CO2, N2, and CI34) will be analyzed using Method <br /> ASTM 1946. Soil samples from the borings will be analyzed for TPHg,total petroleum hydrocarbons as <br /> diesel,BTEX, and fuel oxygenates by EPA Method 8260B or equivalent. <br /> Soil Data Assessment: Following the receipt of analytical results from the laboratory,CRA will evaluate <br /> the soil and soil vapor data to determine whether onsite commercial workers are at risk from the existing <br /> soil and/or groundwater impacts. The soil analytical data will be compared to the surface soil <br /> screening levels for both residential and industrial/commercial exposures presented in the RWQCB's <br /> guidance document entitled, "Screening For Environmental Concerns At Sites With Contaminated Soil <br /> and Groundwater", dated February 2005. The soil vapor results will be compared to the values <br /> published in the document titled Use of California Human Health Screening Levels (CHHSLs) in <br /> Evaluation of Contaminated Properties",published by Cal/EPA in January 2005. <br /> Report Preparation: Following the completion of the data assessment, CRA will prepare a report <br /> discussing field activities, investigation results, assessment results, and recommendations for further <br /> assessment and/or mitigation if warranted. <br /> 1729 4 <br /> Worldwide Engineering, Environmental,Construction,and IT Services <br />