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,,1 ,. ..: ... <br /> Department of Toxic Substances Control <br /> Alan C.Lloyd,Ph.D. 8800 Cal Center Drive Arnold Schwarzenegger <br /> Agency Secretary Sacramento, California 95826-3200 Governor <br /> Cal/EPA <br /> TO: Jerry Lile <br /> Project Manager <br /> Northern California Site Mitigation Branch <br /> 8800 Cal Center Drive, 2nd Floor <br /> Sacramento, CA 95826-3200�j� <br /> FROM: Karen W. DiBiasio, Ph.D. 7 A'6 � � 9-Ca <br /> Staff Toxicologist <br /> Science, Pollution Prevention and Technology Program <br /> Human and Ecological Risk Division <br /> DATE: June 27, 2005 <br /> SUBJECT: DELTA GATEWAY APARTMENTS / L & M OPERABLE UNIT <br /> WORK PLAN FOR SOIL VAPOR ASSESSMENT <br /> PCA Code: 11050 Site Code: 101350 WP: 00 <br /> BACKGROUND <br /> The Human and Ecological Risk Division (HERD) was requested to provide ongoing <br /> toxicology and risk assessment support for Delta View Apartments (formerly Delta <br /> Gateway Apartments) (Site) by the Site Mitigation Program at the Region 1 Sacramento <br /> Office. The Site is located in the City of Stockton, California. The Site is six acres in size <br /> and was formerly used for storage and as a distribution point for petroleum hydrocarbons <br /> off-loaded from ships in the Port of Stockton. In the early 1980's, the Delta Gateway <br /> Apartments were constructed on the western and southern portions of the L & M OU. <br /> There appears to be no evidence that the Stockton Redevelopment Agency (RDA) <br /> conducted any environmental investigation of the Site prior to the construction of the Delta <br /> Gateway Apartments. Previous sampling and analyses have identified dissolved and <br /> separate-phase petroleum hydrocarbons in soil and groundwater as well as volatile <br /> organic compounds (VOCs) including fuel constituents such as benzene, ethylbenzene, <br /> toluene, and xylenes (BTEX), chlorinated solvents, semi-volatile organic compounds <br /> (SVOCs), including polynuclear aromatic hydrocarbons (PAHs); and, metals (notably <br /> arsenic in groundwater and both arsenic and lead in soil). Methane has been detected <br /> in soil gas above the lower explosive limit (LEL) and also in groundwater. Soil gas <br /> analyses have confirmed the presence of VOCs such as petroleum hydrocarbon fuel <br /> constituents including BTEX, confirmed the presence of chlorinated solvents and <br /> identified vinyl chloride contamination, and identified hydrogen sulfide contamination. <br /> Groundwater occurs at 8 to 17 ft below ground surface (bgs) and according to the <br /> CVRWQCB flow is variable although generally to the southeast away from Mormon <br /> ® Printed on Recycled Paper <br />