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F e r i Mr. Jim,Barton h. RWQCB. March 29,2013 Page 15 Strict chain-of-custody protocols will be followed throughout all sample transfers. Chain- of-custody procedures provide an accurate written record tracing the possession of individual samples from the time of field collection through laboratory analysis. The chain-of-custody record will document the samples collected and the analyses requested. Sample Analyses URS' procurement process includes confirming the laboratory chosen is Environmental Laboratory Accreditation Program/National Environmental Laboratory Accreditation Program certified for each analytical method needed. All groundwater and soil samples will be analyzed for TPHg and VOCs using EPA Method SW826013. Soil vapor samples will be analyzed for TPH and VOCs using MethodTO15. Samples collected will be analyzed on a standard 10-day turnaround time. One soil gas sample from each of the three investigation area will also be analyzed to speciate TPH by the length of carbon chains (up to C12), for vapor intrusion risk assessment. One soil gas sample from each investigation area will also be analyzed for oxygen and carbon dioxide to assess aerobic/anaerobic conditions in the soils which may be aiding bio-degradation of TPH. Investigation Derived Waste Soil cuttings and wastewater generated during drilling and groundwater sampling activities will be placed in 55 gallon Department of Transportation approved steel drums, pending disposal. Following receipt of analytical results,, waste drums will be transported to an approved facility for disposal. Assessment Report and Risk Assessment A report will be prepared summarizing field activities, the results of soil gas, soil and _ groundwater sampling, and our conclusions and recommendations. Included in the report will be an updated CSM that will address the comments and recommendations presented in the February 27, 2013, RWQCB letter. The report will also include a screening-level human health risk assessment prepared by the URS project risk assessor. The screening-level human health risk assessment will be performed using the soil vapor and soil data collected from the site. The vapor intrusion assessment will be in accordance with recent DTSC (2011a,b) guidance. The characterization of risk to construction-worker receptors will be performed in general conformance with the DTSC (1994) Preliminary Endangerment Assessment process, including incorporation of more- recent methodological changes in risk assessment (e.g., addressing dermal exposures [EPA, 20041 and inhalation exposures [EPA, 2009]), current toxicity factors, and other procedural recommendations (DTSC, 2011c,d).