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Stantec 76(Former BP)Service Station No. 11192 March 10, 2011 Page 3 not contain petroleum hydrocarbons. Groundwater was not encountered in the former and new UST excavations. Approximately 600 cubic yards of impacted soil were removed from the former gasoline UST excavation and former product piping areas; approximately 800 cubic yards of uncontaminated soil were removed from the new UST excavation; and approximately 350 cubic yards of uncontaminated soil were removed from the former oil USTs. Since well MW-2 was located in the area of the proposed new UST excavation, it was properly destroyed in February 1991 with the oversight of the SJCEHD (IT, Underground Storage Tank Closure Report data April 1991). Soil vapor extraction (SVE) piping, consisting of four-inch diameter perforated casing was installed within the pea gravel backfill at the base of the former fuel UST excavation along the east wall for future remediation of impacted soil (IT, Interim Assessment Report dated December 5, 1991). Between April and July, 1991, IT oversaw the installation of three monitoring wells (MW-5 through MW-7) completed between 40 feet and 45 ft bgs, two SVE wells (VW-1 and VW-2) completed at a depth of 30 feet bgs, and the installation of a soil vapor collection system at the site. Soil samples did not contain petroleum hydrocarbons, except for TPHg in the 20-foot samples from borings MW-7 and VW-2 (550 ppm) and a relatively minor concentration of benzene in MW-7. Petroleum hydrocarbons were not detected in groundwater samples except for relatively minor concentrations of TPHg in well MW-7. (IT, Interim Assessment Report dated October 1991). In January 1992, IT conducted a SVE pilot test using the horizontal piping within the former UST excavation, vadose-zone wells, and existing monitoring wells at the site. The SVE test was conducted over a six-hour period on January 21, 1992. Results of the SVE test indicated that a 100-standard cubic feet per minute (scfm) air flow rate was sufficient to achieve an 85 foot radius of influence (IT, Soil Extraction Pilot Test dated March 1992). In February 1992, IT supervised a hydropunch study, which involved the collection of hydropunch groundwater samples from 11 locations (HP-1 through HP-11). Three of the sampling locations yielded groundwater for sampling. TPHg (380 parts per billion [ppb]was detected in a groundwater sample from HP-5, which was located east of the former fuel UST complex. Concentrations of BTEX were detected in the groundwater sample from HP-1, which was advanced southwest of the former fuel USTs and from boring HP-5 (EMCON, Baseline Assessment Report dated December 27, 1994). Between November 16, 2000 and January 2, 2001, eight weekly groundwater extraction events were performed. During each event, approximately 2,400 to 3,800 gallons of groundwater were removed from well MW-3. In addition, approximately 600 gallons of groundwater were removed from well MW-7 on November 16, 2000. A total of approximately 27,200 gallons of groundwater were removed from the site. Based on the results of groundwater samples periodically collected from well MW-3 prior to and following each of the extraction events, an estimated total of 26.63 pounds (Ibs)of methyl tertiary-butyl ether(MTBE)were removed from beneath the site. The weekly groundwater batch extraction activities were discontinued following the receipt of approval from the SJCEHD. In April 2001, GRI supervised the drilling of eight Geoprobe soil borings (B-1 through B-8) at and in the vicinity of the site, and one CPT boring on-site (CPT-1). Concentrations of petroleum hydrocarbons and fuel oxygenates were not detected in the soil from the CPT boring, or in groundwater samples collected from borings B-3 and B-5 through B-8. MTBE was detected in groundwater samples from borings B-1, B-2, B-4, and the 75-foot groundwater sample from CPT-1 up to a maximum concentration of 120 micrograms per liter (pg/L). Concentrations of di-isopropyl ether(DIPE) and 1,2-dichloroethane (1,2-DCA)were also detected in groundwater from borings B-1 and CPT-1, respectively(GRI, Subsurface Investigation Report dated June 2001). 11192 CPT Investigation WP 3-2011.doc