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—G� <br /> Department of Toxic Substances Control <br /> Alan C,Lloyd,Ph.D. 8800 Cal Center Drive Arnold Schv menegger <br /> AgencySecrelary Sacramento.Callfornla 96826-3200 Governor <br /> CaVEPA <br /> T0: Jerry Lile <br /> Project Manager <br /> Northern California Site Mitigation Branch <br /> 8800 Cal Center Drive,2nd Floor <br /> Sacramento, CA 95826-3200 <br /> FROM: Karen W. DiBlasio, Ph.D., <br /> Staff Toxicologist <br /> Science, Pollution Prevention and Technology Program - <br /> Human and Ecological Risk Division <br /> DATE: March 3, 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 aures in size <br /> and was formerly used for storage and as a distribution point for petroleum hydrocarbons <br /> off-loaded from ships in the Pod of Stockton. In the early 1980's,the Delta Gateway <br /> Apartments were constructed on the westem 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 priorto 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 Papee <br />