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Peter MacNicholl <br /> Page 5 <br /> May 17, 2006 <br /> SPECIFIC COMMENT <br /> Soil Gas Sample Collection, Section 2.2.4, Page 2-21: The Draft SAP states that the <br /> DTSC soil gas guidance will be followed in soil gas sample collection. It further <br /> indicates that procedures on leak check will be performed. HERD would like to remind <br /> USACE the application of tracer gas during sampling to evaluate ambient air intrusion to <br /> the samples. <br /> DISCUSSION and CONCLUSION <br /> HERD's comments on the Draft SAP for OU2, DDJC-Sharpe, are noted above. By the <br /> resolving our comments above, HERD will be able to accept the SAP. In addition, we <br /> recommend consulting the Central Valley RWQCB on potential beneficial use of the <br /> groundwater underlying the site. Since the document does not contain any details on <br /> preparation of the updated HHRA, HERD defers our comments on the risk assessment <br /> until we receive and review the updated HHRA for the 01-12. <br /> If you have any questions or concerns, please contact me at (916) 255-6438. <br /> Reviewed <br /> Reviewed by Michael J. Anderson, Ph.D. ptyp , y T A <br /> Staff Toxicologist <br /> Human and Ecological Risk Division <br /> REFERENCES <br /> 1. Cal EPA, Department of Toxic Substances Control (2005). Interim Final <br /> Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air <br /> Vapor Intrusion Guidance. <br /> (http://www.dtsc.ca.gov/AssessingRisk/upload/HERD_POL_Eval_Subsurface_Vapor_I n <br /> trusion_interim_final.pdf) <br /> 2. USEPA, Office of Emergency and Remedial Response, EPA/540/1-89/002 (1989). <br /> Risk Assessment Guidance for Superfund Volume I Human Health Evaluation Manual <br /> (Part A) Interim Final. (http://www.epa.gov/oswer/riskassessment/ragsa/pdf/preface.pdf) <br />