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V V ,r Removal of 1,000 -Gallon Diesel UST System (1996) A 1,000 -gallon diesel UST system was located on the western side of the building and was used y to supply fuel to a boiler. The UST system was removed for permanent closure in February 1996 (PSC, 1996). The analytical data for soil samples collected from the excavation of the UST system indicated no environmental issues. v 2.5.2 Subsurface Investigations, Remediation, and Monitoring The following sections summarize information pertaining to investigation, remediation, and monitoring activities performed at the site. Analytical data for soil samples collected during investigation activities are included in Table 1. Analytical data for groundwater samples collected during investigation and monitoring activities are included in Table 2. i.. Subsurface Investigations (1987 through 1994) In July and September 1987, ESE installed groundwater monitoring wells MW -1, MW -2, and y MW -3. Between January 1988 and September 1990, ACG installed groundwater monitoring wells MW -4 through MW -8. -In February 1990, ACG drilled soil borings 90-1 and 90-2. PSC Environmental Services (PSC) (formerly Burlington Environmental) installed wells MW -9 �. through MW -13 in March 1994, piezometers PZ -1 and PZ -2 in September 1994, and air sparging well SP -1 in September 1994.' Locations of the wells and borings are presented on Figure 2B. Soil samples were collected from most of the borings during drilling and submitted for laboratory analysis. The analytical data for soil are presented in Table 1. The samples contained TPH-g up to 130 mg/kg, benzene up to 0.010 mg/kg, toluene up to 0.038 mg/kg, ethylbenzene up to 0.005 mg/kg, and xylenes up to 0.12 mg/kg. 4 Soil Vapor Extraction Pilot Test (1994) V PSC performed a soil vapor extraction (SVE) and air sparging (AS) pilot test in October and November 1994 to evaluate the effectiveness of these remediation technologies at the site. SVE �., tests were performed using well MW -1, and air sparging tests were performed using well SP -1. PSC reported the results of the tests in the February 1, 1995 Final Remediation Plan, which indicated that SVE and air sparging would be effective for the remediation of hydrocarbons in the subsurface. In June 1995, PSC installed air sparging wells SP -2 through SP -6. However, implementation of the air sparging and SVE system was postponed due to naturally -occurring reductions in petroleum hydrocarbon concentrations that were observed at the time. V 64 L_ Subsurface Investigation (1999) In May 1999, PSC performed a subsurface investigation using CPT technology. Soil and groundwater samples were submitted for laboratory analysis from three CPT borings (CPT -1, 6