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t, 45 E Harding Way, Stockton, Caldomia Mune 17, 1994 Chevron USA Products Company Page 2 2.0 BACKGROUND The site, currently an empty lot, was formerly a Chevron service station which retailed gasoline from 1953 to 1988 Gasoline had been dispensed from pump islands located on the eastern and southern portions of the site The majority of the gasoline dispensed was supplied to the pump islands from three underground storage tanks (USTs) located in the tank pit on the south-central portion of the site Fiberglass tanks were installed in the main UST pit In 1984 during station remodeling Service station operations ceased in 1988 and the fiberglass tanks were removed Environmental investigation began at the site in 1987 Numerous investigations have been completed at the site and are summarized in reports submitted to the SJCPHS-EHD (EA Engineering, Science and Technology, April 16, 1991, and Groundwater Technology, Inc, March 14, 1994) Environmental assessment has been focused on mapping the extent of hydrocarbons in soil and groundwater related to unauthorized releases from the main UST pit A soil vapor extraction system designed to remediate hydrocarbon-impacted soil in and around the main UST pit and dispenser area operated at the site from . November 1990 through November 1992 Analysis of soil samples collected from soil borings drilled adjacent to former vapor extraction wells in December 1993 Indicated the presence of residual hydrocarbon-impacted soils (Groundwater Technology, Inc , March 14, 1994) Quarterly groundwater monitoring and sampling has been conducted at the site since November 1988 Groundwater monitoring wells MWs-13 and 14 define the approximate downgradient boundary of the dissolved hydrocarbon plume Because the site had retailed gasoline since the early 1950's, many generations of USTs and appurtenances were present In addition to the main UST pit, separate USTs have been located along the southeastern portion of the site while drilling and excavating in two different areas shown on Figure 2 (EA, April 16, 1991, and Groundwater Technology, March 14, 1994) Review of historic photos, facility plans and tank removal reports of the site indicated that another former UST area was present in the northeastern portion of the site (Figure 2) A geophysical survey was conducted at the site in February 1994 to identify/confirm the remaining in-situ USTs The geophysical survey showed no evidence of any tanks remaining in the shallow subsurface �—ClW GROUNDWATER as2rnnR oar R ii F_Cl TECHNOLOGY