ARCHIVED REPORTS_REMEDIATION COMPLETION REPORT

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2.0 Background The site is located on a private access road approximately one half mile north of the intersection of Thornton Road and Barber Road,and approximately two miles north of the town of Thornton in unincorporated San Joaquin County, California (Figure 1). The site is surrounded by a chain link fence and measures approximately 50 feet wide by 150 feet long (Figure 2). The site is abutted directly to the west by a utility easement within a vegetated drainage feature. A fiber optic line is buried near the surface within the drainage feature. Adjacent to the drainage feature is a railway line on top of an embankment. A Sprint fiber optic line abuts the site to the east. Photographs of the site are shown in Appendix A. PG&E built the dehydrator station in 1962 to dehydrate and odorize natural gas for transport in its gas transmission system(CH2M HILL 1998).The site formerly contained a control building, three contactor towers, two sumps,two production fluids tanks,two reboiler units and an associated glycol storage tank,an odorizer unit and an associated odorant tank. In 2005,PG&E deactivated the station and disconnected and removed all equipment prior to remedial excavation. The site is bordered on the north,east,and south by private agricultural properties,and the west side boundary is bordered by a Union Pacific Railroad (UPRR) elevated railroad line. Groundwater quality at the site is currently being monitored under Monitoring and Reporting Program No.5-01-860 order from the CVRWQCB (CH2M HILL 2004b). As part of this program, three offsite monitoring wells (NMW-3,NMW-4 and NMW-5) are being monitored along with one onsite well and four piezometers. Remedial activities performed at the site consisted of: • Abandonment of one groundwater monitoring well (MW-1) and three piezometers (PZ- 2 through PZ-4) under San Joaquin Environmental Health Department permit. • Removal of underground piping and demolition of existing concrete foundations. • Excavation of soil containing petroleum hydrocarbons and transporting the soil off-site to an approved and permitted disposal facility. • Verification sampling and analysis. • Restoration of the site. Applicable excavation and grading permits were obtained from San Joaquin Environmental Health Department and San Joaquin Community Development Department,respectively, prior to commencing field activities. Copies of these permits are included in Appendix B. 2.1 Project Roles and Responsibilities CH2M HILL, Inc. (CH2M HILL) and CH2M HILL Constructors,Inc. (CCD were responsible for implementing the remedial field activities. CH2M HILL personnel included design SFO1(THORNTON COMPLETION REPORT_$-21-05.DOC) 2-1