SITE INFORMATION AND CORRESPONDENCE

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16.1 CHRONOLOGY Caltrans Shop 10 1603 B Street Stockton, CA 95206 08/25/87 Four groundwater monitoring wells (MW1-MW4) were installed beginning this date, under EHD permit and inspection. See Woodward-Clyde report dated November 11, 1987 available on microfiche. 06/11/88 A soil gas survey was performed around the underground storage tank (UST) system. Twenty-six soil gas samples were collected at depths ranging from 7-33 feet below surface grade (bsg); most reported petroleum hydrocarbon contamination. See Woodward-Clyde's Problem Assessment Report dated August 16,1990 available on microfiche. 08/18/88 An Unauthorized Release Report was filed this date. 02/16/89 Four gasoline UST's were removed this date under San Joaquin County Environmental Health Department (EHD) permit and inspection. 02/22/89 Soil samples for laboratory analysis were collected this date from beneath the UST area, after removal of a cement slab. Discoloration and hydrocarbon odor were noted in the soil. Laboratory analytical results subsequently reported TPHd, TPHg, benzene, ethylbenzene, toluene, and xylenes in the samples. 03/27/89 One waste oil UST was removed this date under EHD permit and inspection. No odor or discoloration was noted in the soil beneath the tank. Laboratory analytical results reported maximum 12-ppm TPHd in the samples (see 4/10/89 Alpha Analytical Laboratories, Inc. report in LOP file). 03/01/90 Groundwater elevation dropped and MW-1 through MW-4 were dry; five soil borings were advanced and converted to groundwater monitoring wells, MW-5 through MW-9, starting this date. See Woodward-Clyde's Problem Assessment Report dated August 16, 1990 available on microfiche. 03/30/92 Three monitoring wells, MW-10, MW-11 and MW-12, and two soil borings, AB-1 & AB-2, were installed starting this date. See Alton Geosciences Supplemental Site Assessment Report dated July 13, 1992. 04/01/92 Notice of Reimbursement (NOR) sent this date to property and tank owner, California Department of Transportation. 05/28/92 A soil vapor extraction test was conducted on dry monitoring well MW-10. See Alton Geosciences Soil Vapor Testing Report dated September 22, 1992. 11/02/92 Notification of Hazardous Waste Discharge #92-221 submitted this date. 10/14/93 Monitoring wells MW-13, MW-14, MW-16, MW-19, MW-20, MW-24 and borings SB-15, SB-17, SB-18, SB-19, SB-21, SB22, and SB-23 installed beginning this date. See Environmental Assessors Inc. Site Assessment Report dated January 13, 1994.