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MEMORANDUM-' - <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 <br /> TO: Antonia Vorster FROM: Michael Higgins <br /> Senior Engineer Associate Engineer <br /> DATE: 17 October 1991 SIGNATURE: . <br /> SUBJECT: CALIFORNIA FUELS SITE, 838 MOKELUMNE STREET, WOODBRIDGE, SAN JOAQUIN COUNTY <br /> The California Fuels site in Woodbridge, San Joaquin County formerly held several <br /> aboveground fuel tanks, which spilled or leaked fuels into the surrounding soils. <br /> Aegis Environmental Consultants (AEC) sought to clean up the site by excavating the <br /> polluted soil , removing it to a nearby landing and reducing the fuel component <br /> concentrations to acceptable levels via bioremediation. AEC reported the results of <br /> sampling the excavation and the treated soil pile in the 7 June 1991 Report of <br /> Excavation and Soil Stockpile Analytical Testing. <br /> In reviewing the report, I have determined that the extent of the pollution was not <br /> determined before AEC backfilled the excavation with clean fill . The attached <br /> Figures 4, 5, 6 and 7 demonstrate this, providing the results of the analyses of <br /> soil samples taken from the excavation's bottom as it was progressively deepened in <br /> five-foot stages. <br /> Figure 4 provides the analytical results of several soil samples obtained from the <br /> northwest portion of the excavation when 10 feet deep. All samples from this sector <br /> at this depth contained substantial concentrations of fuel components, as shown <br /> below: <br /> FUEL COMPONENTS IN SOIL SAMPLES AT 10 FONT DEPTH, MG/'KG <br /> Sample Ethyl TPH TPH <br /> Number Benzene Toluene Xylenes Benzene Gasol . Diesel <br /> NES-41 2.3 8.6 37 7.0 300 4, 100 <br /> NES-42 5.1 6.3 29 8.6 400 11,000 <br /> NES-43 2.1 1 .9 11 4.3 250 6,700 <br /> Samples containing these high concentrations indicate that samples should be taken <br /> from the same locations at the next sampling depth; that is, at 15 feet deep. <br /> However, AEC took no samples anywhere in the northwest sector of the excavation at <br /> or deeper than 15 feet deep. It is, therefore, impossible to determine whether or <br /> not excavation removed the polluted soil discovered at 10 feet deep. <br />