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Stantec NOW, N%0011 No Further Action Request Report Chevron and ARCO Commingled Plume No. CP0034 April 10, 2012 mg/kg, and 124 mg/kg, respectively. Di-isopropyl ether, tert amyl-methyl ether, ethyl tert-butyl ether, tert-butyl alcohol, and ethanol were reported as non-detect in all soil samples. Approximately 450 tons of soil generated during the UST, product line, and dispenser removal activities was removed from the site and disposed of at BFI's Landfill in Livermore, California (SECOR 1999). One 550-gallon, double-walled, fiberglass waste oil UST was removed from the site in 2002. The tank appeared to be in good condition with no holes or cracks. One soil sample (WT-1) was collected from the center of the tank pit at a depth of approximately 11 ft bgs. Hexavalent chromium, chromium, nickel, zinc, and lead were reported at concentrations of 1.4 mg/kg, 35 mg/kg, 38 mg/kg, 49 mg/kg, and 12 mg/kg, respectively. All other constituents analyzed for were reported as non-detect (SECOR 2002). 2.4.2. Site Assessment History Chevron 94275 Facility Four soil borings (SB-1 through SB-4), nine groundwater monitoring wells (MW-1 through MW- 9), and ten soil vapor extraction/air sparge (SVE/AS) wells (GM-1 through GM-9 and VW-1) were installed onsite and offsite from 1989 through 2006. Soil samples collected and analyzed during the installation of monitoring wells MW-3, MW-4, and MW-6 through MW-8 did not report any detections of GRO or benzene above the laboratory MRL. Soil boring and well construction details are presented in Table 1. Historical soil analytical data is included in Table 3. In 2001, a cone penetrometer test (CPT) investigation consisting of five borings (CPT-1 through CPT-5) was conducted along the eastern side of Plymouth Road to assess soil stratigraphy and collect discrete groundwater samples. Groundwater samples were collected from the identified water-bearing zone or depth intervals showing distinct pore pressure. Three to four depth- discrete groundwater samples per boring were submitted for analysis. Groundwater samples were generally collected at depths of ten to 12 ft bgs, 24 to 25 ft bgs, 35 to 40 ft bgs, and 68 to 78 ft bgs. GRO was detected in two of the 17 groundwater samples at concentrations of 73 micrograms per liter (pg/L) (CPT-5 at 37 ft bgs) and 130 pg/L (CPT-3 at 40 ft bgs). MTBE was detected in six of the 17 groundwater samples at concentrations ranging between 0.59 pg/L (CPT-4 at 10 ft bgs) and 2.6 pg/L (CPT-5 at 37 ft bgs). The site was demolished in June 2005. In preparation for site demolition, seven on-site groundwater monitoring wells (MW-1 through MW-5, MW-7, and MW-9) and ten SVE/AS wells (VW-1, GM-1 through GM-8, and GM-9) were destroyed in May 2005. Replacement monitoring wells were installed in February 2006 following completion of the station rebuild. 94275 NFAR 2012.doc 7