SITE INFORMATION AND CORRESPONDENCE

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California Regienal Water Quality Con*rol Board 'NoCentral Valley Region NEW Terry Tamminen Robert Schneider,Chair Arnold Schwarzenegger Secretary for Governor Environmental 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114(916)464-3291 Protection http://www.swrcb.ca.gov/rwgcb5 TO: Brian Newman/'. Senior Water Resources Control Engineer Gordon Boggs UST Program Manager FROM: James Barton Engineering Geologist DATE: 22 MARCH 2004 SUBJECT: REVIEW OF NO FURTHER ACTION REQUEST, UNDERGROUND STORAGE TANK, SILGAN CONTAINER CORPORATION, 1815 NAVY DRIVE, STOCKTON, SAN JOAQUIN COUNTY Background: Silgan Container Corporation(Silgan), formerly Canaco, a division of Carnation Can, 1815 Navy Drive, Stockton (Figure 1), owned and operated one 3,500-gallon concrete paint thinner(solvent) underground storage tank(UST). The UST(Figure 2)was reported removed in October 1986 as witnessed by San Joaquin County Environmental Health Division (SJCEHD). The seals between the concrete slabs may have deteriorated,resulting in a release of chlorinated solvents and waste petroleum hydrocarbons. Chemical odors were reported from approximately 20 cubic yards of soil were removed with the UST. The contaminated soil was aerated onsite and placed into the UST excavation. Analysis of the residue sludge from the tank revealed tetrachloroethene (PCE, 59,000 gg/L),trichloroethylene(TCE, 2,000 µg/L) and ethylbenzene(20,000 µg/L). Maximum analytical results from soil and grab groundwater investigations conducted from July to October 1987 are included as Table 1. Three monitoring wells (MW-1,PW-1, and PW-2) were installed in July 1987. The 1987 groundwater monitoring results are included as Table 2. Depth to first water is approximately 18 feet below ground surface. Shallow groundwater flow direction varies across the site, from southeast to southwest(south of UST)and northeast(east of UST),with a gradient from .002 to .006 feet/feet. Soils beneath the site consist of sand, silt, and clay to 35 feet below ground surface, the total depth of the investigations. The Phase II Site Characterization—P.A.R (PAR), dated 13 March 1990,included the January-February 1990 installation and sampling of three additional monitoring wells (GW-1, GW-2, and GW-3). Results of the soil and -- groundwater investigation are included in Table 3. The PAR stated approximately 450 cubic yards of contaminated soil existed as backfill in the UST excavation. The PAR proposed remedial alternatives were soil over-excavation and offsite transport, soil excavation and onsite biotreatment, soil vapor extraction (SVE), and no action. SVE was the preferred alternative. The PAR was never implemented, and no additional groundwater monitoring or investigations were conducted from 1991 to 2001. California Environmental Protection Agency Qd Recycled Paper