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UPgradid- t Environmental fnsultants • December 14, 1998 l% Mr. Tom Nicholas ^ Magnolia Realty 3911 Waynesboro Ct. Stockton, CA 95219 Subject: Preliminary Environmental Assessment Electro Delta Co. 821 S. Wilson Way Stockton, CA Dear Mr. Nicholas: Upgradient Environmental Consultants has completed the scope of work authorizec. under project no. 98036 and is pleased to transmit herewith the results of our investigation The investigation centered around an underground gasoline storage tank that was used by previous owners of the property to fuel company vehicles. When that 500-gallon tank was removed in 1985, a soil sample was collected from beneath it and lead-was detected at a concentration of 407 mg/kg (parts per million {ppm)) in the sample. In the Stockton area, the normal background concentration of lead in the soil from non-petroleum sources is between 10 and 20 ppm. Hence,the elevated concentration suggested that the tank may • ' have leaked leaded gasoline. In order to determine whether the lead is soluble in water and could contaminate groundwater beneath the site, San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD), directed Upgradient to drill one boring through the former tank pit in order to collect a sample at a depth of 15 feet. PHS/EHD further directed that the sample should be analyzed for soluble lead usin€, the Cal-WET test. Upgradient submitted a work plan and drilling permit to PHS/EHD is i early October,and the work was performed on November 25. Mitchell Drilling Environmental of Rancho Cordova used a truck-mounted CME-7� hollow-stem auger drilling rig. I examined samples of the soil during drilling, and recorded my observations on the attached boring log. Near the surface, the soil is re(- brown sand, but clay becomes more common downward. Below 8 feet, the soil is sticky brown clay and silty clay. An odor of gasoline was evident below 12 feet and in the sample collected at the bottom of the hole(15 feet). Therefore, with the concurrence of Ms. Carol Oz of PHS/EHD, I directed the laboratory to analyze the sample for benz<!ne, toluene, ethylbenzene, xylene(BTEX),methyl-tertirary-butyl ether(MTBE)and gas oline (purgeable hydrocarbons) using EPA methods 8020 and 8015 as well as for soluble lead. The laboratory report is attached to this report. Gasoline was detected at a concentration of 4,890 ppm, toluene was detected at 236 ppm, ethylbenzene was detected at 110 ppm, and xylene was detected at 433 ppm. The rel hive concentrations of the latter three compounds and the absence Af the volatile and easi y- • removed benzene indicate that the gasoline is partly degraded ("weathered"gas according Stockton: P.O. Box 8002,Stockton, CA 95208 (209) 772-3620 Cameron Park: 3369 Kimberly Road, Cameron Park, CA 95682 (916) 677-3055