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I 2. SITE BACKGROUND 2.1 SITE LOCATION AND LAND USE Former Exxon RS 7-3942 is currently a vacant lot located on the southeast corner of the intersection of North Pershing Avenue and Rosemarie Lane (Figure 2) Used oil and three grades of gasoline were stored in four underground storage tanks (USTs), which were removed from the site in July 1986 Land use in the vicinity of the site is primarily commercial and residential A Shell service station and a 7-Eleven food and gasoline service store are located on the southwest and northwest corners, respectively, of the intersection of North Pershing Avenue and Rosemarie Lane Details concerning these sites are presented in Section 2 6 The Chateau Hospital convalescent home is located approximately 200 feet northwest of the site across Rosemarie Lane There is an apartment complex to the east of the site and a commercial building to the south (Figure 2) Stagg High School is located approximately 1,500 feet southwest of the site as Ipresented on Figure 1 2.2 SITE HISTORY AND SUMMARY OF PREVIOUS INVESTIGATIONS One used-oil and three gasoline USTs were removed in July 1986 Following UST removal activities, seven soil samples (EX1-EX7) were collected in September 1986 at approximately 20 �• feet below ground surface (bgs) at the bottom of the expanded excavation Three of the seven samples contained Total Petroleum Hydrocarbons (TPH) and benzene concentrations of up to 6,900 mg/kg TPH and 77 mg/kg benzene Additionally, four soil confirmation samples (ES1 ' through ES4) were collected at a depth of approximately 2 feet bgs under product piping and analyzed for benzene, toluene, ethylbenzene, and total xylenes (BTEX) in December 1986 These samples did not contain benzene above reported detection limits (Appendix B) Onsite ' groundwater monitoring wells MW1 MW7 and offsite wells MW8—MW10 were installed between January 1987 and April 1988 Groundwater recovery wells RW1—RW3 were installed onsite in May 1990 The locations of wells are shown in Figure 3 Groundwater monitoring and sampling was initially conducted in January 1987, and has been conducted on a quarterly basis since February 1989 Samples are submitted to a state-certified laboratory and analyzed for BTEX and for TPH as gasoline (TPH-g) Since 1995 groundwater samples have also been analyzed for methyl tertiary butyl ether (MTBE) Historical groundwater analytical results are presented in Table 1 The analytical results of the most recent groundwater sampling event (18 December 2002) are graphically presented in Figure 3 The December 2002 quarterly groundwater monitoring report will be issued under separate cover In October 1990, EA Engineering, Science, and Technology (EA) submitted a Combined Work Plan to Remediate Soil and Groundwater (EA 1990) Under this plan, EA proposed a groundwater extraction, treatment, and reinfection system Pursuant to the 1990 plan, EA installed the required wells for this remedial approach From January to April 1991, wells IW1, P1, P2, V1, V2, and V4 were installed onsite, and wells RW4, V3, MW11, and MW12 were installed offsite Figure 3 shows the locations of former site facilities and the locations of all ExxonMobil wells on and off the site The locations of offsite monitoring wells MW8, MW9, G SPrqcctBN73942\f i STERIWP\WP03031WPix doc 2