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E C 0 R <br /> QUARTERLY SUMMARY REPORT <br /> THIRD QUARTER 2003 <br /> 76 Service Station #5886 <br /> 2701 West March Lane, Stockton, CA <br /> City/County ID # Stockton <br /> County San Joaquin <br /> BACKGROUND <br /> Union Oil Company of California (Unocal) purchased the land in 1967, at which time the property <br /> was vacant In 1982, Unocal constructed a service station at the site and installed three 12,000- <br /> gallon underground storage tanks (USTs) to store gasoline and diesel fuels (Delta Environmental <br /> Consultants, Inc [Delta], February 6, 1996) <br /> As presented in previous reports, a summary of site activities including remedial efforts at the site is <br /> as follows <br /> 1995 — Unocal removed three 12,000-gallon fuel USTs, product piping, and dispensers <br /> Unocal replaced the fuel USTs with two 15,000-gallon and one 12,000-gallon UST The <br /> UST replacement activities included disposal of approximately 1,200 cubic yards of soil at <br /> Forward Landfill in Manteca, California and disposal of approximately 15,000 gallons of <br /> groundwater at Unocal's Rodeo, California facility (Delta, February 6, 1996) <br /> September 1995 - Unocal advanced 21 soil borings and collected soil and groundwater <br /> samples from the borings utilizing a Geoprobe®sampling system (Delta, February 6, 1996) <br /> June 1996 - Pacific Environmental Group, Inc (PEG) performed a water-supply well survey <br /> within a one-quarter-mile radius of the site The survey identified 10 wells located within the <br /> survey area These wells are located northeast to southeast of the site and are apparently <br /> utilized as cathodic protection or irrigation wells (PEG, June 24, 1996) <br /> • September 1996- Unocal drilled four additional soil borings, and constructed groundwater <br /> monitoring wells in three of these borings (Delta, December 5, 1996) <br /> March 1997—Tosca submitted a Work Plan for Supplemental Environmental Investigation <br /> (ERI, March 28, 1997)to the County <br /> April 1997—Tosco submitted an Addendum to Work Plan (ERI, April 3, 1997) to the County <br /> April 1997—Tosco performed a soil and groundwater investigation at the site The <br /> investigation included hand-auguring three soil borings adjacent to catch basins, drilling four <br /> soil borings, and constructing dual-completion groundwater monitoring wells (MW4SID <br /> through MW7SID) at discrete depths in the borings (ERI, June 3, 1997) <br /> July 1997—Tosco submitted a Work Plan for Supplemental Environmental Investigation <br /> (ERI, July 14, 1997) to the County <br /> August 1997 —Tosco submitted the Addendum to Work Plan(ERI, August 8, 1997) <br /> to the County <br /> • July 1997 through December 1998—Tosco performed an underground utility search <br /> (ERI, October 6, 1997) (Plate 2), continued to perform quarterly groundwater monitoring and <br /> sampling, obtained access agreements to drill soil borings at select properties located south <br />