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Attachment A:Previous Environmental Activities chemicals were associated with the disposal of petroleum waste or mop water into the septic tank during a one-time event. Geological Technics concluded that two overlapping plumes were present on the Site: (1) a TCE plume caused by a surface release of cleaning solutions years ago by Hunter Container, and (2) a petroleum-hydrocarbon plume sourced from one or both of the two petroleum pipelines located approximately 34 feet northeast of the Hunter Container building, and owned by Southern Pacific Pipeline Company and Chevron. Geological Technics recommended that"San Joaquin County and RWQCB work with the two pipeline companies to address the petroleum hydrocarbon issue." RADIAN INTERNATIONAL,LLC (RADIAN) 1997 GROUNDWATER INVESTIGATION' On February 27, 1997, Radian was contracted by CPL to conduct a limited groundwater investigation at the Hunter Container property to determine if TCE had affected the groundwater. Radian advanced three cone penetration test(CPT) borings (CPT-1, CPT-2, and CPT-3), and groundwater samples were collected at two distinct intervals (35 and 50 feet bgs) and tested by an analytical laboratory. TCE was not detected in any sample. Cis-1,2-dichloroethene, a degradation product of TCE, was detected in one of the groundwater samples at a concentration below the United States Environmental Protection Agency (EPA)Maximum Contaminant Level (MCL)for drinking water. Radian concluded that"TCE and other chlorinated organic hydrocarbons have not impacted groundwater." RADIAN 1998 SITE INVESTIGATION In July 1998, six soil borings (B-1 through B-6)were advanced at Hunter Container and three monitoring wells (MW-2, MW-3, and MW-4) were installed. TPHg, TPHd, and TPHmo were detected in borings B-1, B-4, B-5, B-6 and monitoring well MW-2. Elevated concentrations of TPHg(1,400 mg/kg) were detected in B-5 at 10 feet bgs, and TPHd(21,000 mg/kg) and TPHmo (15,000 mg/kg) were detected in B-5 at 20 feet bgs. Laboratory analytical results indicated TPHd concentrations of 2,300 and 300 gg/L in wells MW-2 and MW-3, respectively, and a TPHmo concentration of 700 gg/L in MW-2. No other constituents of potential concern (COPCs)were detected in groundwater samples. GEOMATRIX CONSULTANTS,INC. (GEOMATRIX)2000 SOIL AND GROUNDWATER INVESTIGATION$ On November 9 through 11, 1999, at the request of Chevron Environmental Management Company(CEMC), Geomatrix advanced seven soil borings (GMX-1 through GMX-7)to assess the vertical and lateral extent of affected soil and groundwater. Borings GMX-6 and GMX-7 were advanced off site, on the east side of Highway 33. Additionally, groundwater samples were collected from monitoring well WFSMW-1 on the Western Farm Service (now Crop Production Services [CPS]) property and tested for the COPCs. 6. Radian, 1997. 27 February 1997 Groundwater Sampling at 35275 Welty Road, Vernalis, California. March. 7. Radian, 1998. Site Investigation at 35275 Welt} Road, Vernalis,California. 8. Geomatrix,2000. Soil and Groundwater Investigation Report,35275 Welty Road,APN 255-180-09, Vernalis, California. February.