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Stockton Meat Plant - Case Closure Page 2 March, 1996 The site is paved, with the exception of landscaped areas and an undeveloped parcel north of the meat processing plant The soils beneath the site consist primarily of silts, clays, and bay mud Ground water has varied between 19 and 26 feet below mean sea level during the project I PREVIOUS WORK ` Work performed at the site has been documented in several reports prepared by contractors and consultants Field activities included precision testing of I underground tanks and pipeline, identifying leaks in tankage, determining the extent of petroleum hydrocarbons in soil and ground water, excavating and bioremediating soils, removal and disposal of ground water, installation of ground water monitoring wells, and quarterly monitoring of ground water for 8 sampling events between February 1992, and March 1995 Underground Tank Testing 1987 In February and March 1987, Safeway contracted to have the four underground diesel fuel tanks precision tested by a certified contractor One tank did not pass the test (Attachment A, March 4, 1987 letter from Precision Industries) Accordingly, an Underground Storage Tank Unauthorized Release (Leak) Contamination Site Report was filed with the State of California (Attachment A) Summary Re ort 1987-88 ' In response to the reported tank leak, several investigations and remediation actions were initiated and performed at the site, from April, 1987 to ' September, 1988 The work consisted of installing preliminary borings to identify the extent of the release, removal of tanks, over-excavation of hydrocarbon impacted soils, and installation of three ground water monitoring wells A summary of the previous work is included in Appendix B - copied from Western Geologic Resources, Inc letter "Tank Excavation and Former Sampling", dated April 3, 1989 ' By September, 1988, over 1,200 cubic yards of soil were excavated from the tank site and stockpiled on site The last round of soil excavation ' concentrated in the southwest corner of the previous tank site The extent of the excavation was limited in the southern direction because of Navy Drive Preliminary excavation sampling indicated hydrocarbon concentrations reported as diesel at 3,700 mg/kg at 13 feet below ground surface (TP-N-7A) Subsequent excavations adjacent to the tank site (just outside the concrete tie- down slab) to a depth of greater than 24 feet were reported with non- detectable concentrations of hydrocarbons (Figure 9, Summary Report, TP-23, } TP-24, TP-26, and TP-27) After excavation to approximately 24 feet below ground surface, residual hydrocarbons were encountered at about 20 feet