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`- Department of Toxic Substances Control <br /> v > . <br /> Edwin F. Lowry, Director <br /> Terry Tamminen 8800 Cal Center Drive Arnold Schwarzenegger <br /> Agency Secretary Sacramento, California 95826-3200 Governor <br /> Cal/EPAED <br /> April 15, 2004 APR 2 0 2004 <br /> ciJVIKOINNIENT PERMIT/SERVICES HEALTH <br /> Mr. Maurice Benson <br /> Environmental Office <br /> Building 100 <br /> Post Office Box 9600001 <br /> Tracy, California 95296-0250 <br /> COMMENTS ON DRAFT VAPOR INTRUSION SAMPLING WORK PLAN, FOR <br /> DEFENSE DISTRIBUTION DEPOT (DDJC)-SHARPE FEBRUARY 2004, LATHROP, <br /> CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC), received the above-mentioned <br /> work plan on March 26, 2004. The vapor-intrusion work plan was prepared in response <br /> to comments from the DTSC on a potential exposure pathway identified for Volatile <br /> Organic Compounds (VOCs) in shallow Ground Water (GW) beneath buildings located <br /> on DDJC-Sharpe during the review of the Draft Five-Year Review Report. <br /> The vapor intrusion sampling work plan proposes to take a total of ten Cone <br /> Penetrometer Testing® shallow sub-surface soil vapor samples over three areas where <br /> Trichloroethene (TCE) concentrations in GW are greater than 25 pg/L in shallow A-zone <br /> aquifer. The samples will be taken at depths of three feet and six feet below ground <br /> surface. The three foot samples represent the approximate depth of bottom of a <br /> building foundation. The soil gas samples will be collected in 1.0 litre SUMMA® <br /> canisters for analysis of any VOCs detected by United States Environmental Protection <br /> Agency Total Organic 14 Method. Any detected concentrations of VOCs in soil gas will <br /> be used in the Johnson Ettinger Soil Vapor Intrusion Model to evaluate potential risks to <br /> workers in a building over the sampled areas. <br /> Field work will be scheduled in early spring as funding is appropriated. DTSC and the <br /> Regional Water Quality Control Board will be represented during the actual field work to <br /> ensure work is carried out as planned. <br /> DTSC concurs with the tasks and sampling methodology proposed in the vapor <br /> intrusion sampling work plan. <br /> ® Printed on Recycled Paper <br />