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' 40 SITE HISTORY,LITHOLOGY,AND AREA HYDROGEOLOGY . 4.1 Site UST History The general site location is shown in Figure 1,Vicinity Map and Figure 2, Previous Site Jnvestigation Map — Soil Borings/Groundwater Monitor Wells (NE, August 1991, TPE, June/July 1992, HET, December 1993, ' BC, December 1994/Janaury 1995, Clearwater, June 2001), illustrates the former underground storage tank (UST) system ATC understands that the UST system was removed in March 1990 The former UST system consisted of one 8,000-gallon gasoline UST, three 10,000-gallon gasoline USTs, and one-fuel dispenser island The USTs were located in the central portion of the property The dispenser island was located at the southeastern corner of the property Based on field observations and analytical results it appears that the USTs were suspected to be the source of the release The site is currently occupied by E-Z Market There are no USTs or dispenser islands currently on-site ' 4.2 Previous Site Characterizations - Soil In August 1984, Nachant Environmental Inc (NE) conducted an initial phase of assessment as a result of a suspected fuel system leak The assessment consisted of installation of drilling three soil borings, designated as B-1 through B-3 B-1 was drilled in the former UST excavation B-2 was advanced near the southwestern corner of the property B-3 was drilled neat the southeastern comer of the pr6perty B-1 rwas advanced to an approximate depth of 50 feet below ground surface (bgs), and B-2 and B-3 were each drilled to an approximate total depth of 41 5 feet bgs Boring locations are illustrated on Figure 2 �. Elevated levels of fuel hydrocarbon constituents were detected in the 20 and 40-foot samples obtained from B-1, and the 35-foot sample collected from B-3 Low to non-detect levels of petroleum hydrocarbon constituents were detected in the other soil samples obtained from soil borings B-1 through 13-3 submitted for rlaboratory analysis Analytical results obtained during the UST removal activities are summarized in Table 1, Previous Site Investigation-- Soil Borings/Groundwater Monitor Wells— Soil Sample Analytical Results (NE, August 1991, TPE, June/July 1992, HET, December 1993, BC, December 1994/Janaury 1995, Clearwater, June 2001) Details of this assessment are presented in the NE Preliminary Site Assessment Report, dated November 22, 1991 In June and July 1992, Tank Protect Engineering (TPE) performed a subsequent phase of assessment During this investigation, five groundwater monitor wells, designated as MWA through MW-5, were installed on-site MW-1 was installed in the central portion of the former UST excavation MW-2 was installed approximately 15 feet northwest of the former UST excavation MW-3 was installed approximately 15 feet northeast of the former UST excavation MW-4 and MW-5 were installed on-site at the southeastern and southwestcm corners of the property, respectively MW-1 through MW-3 were completed to an approximate depth of 91 feet and screened from 71 to 91 feet bgs MW-4 and MW-5 were completed to an approximate depth of 92 feet and screened from 72 to 92 feet bgs Elevated levels of fuel hydrocarbon constituents were detected in the 48 8-foot sample obtained from MW-1, the 21 5- foot sample collected from MW-3, and the 36 5-foot sample collected from MW-4 Low to non-detect levels of petroleum hydrocarbon constituents were detected in the other soil samples submitted for laboratory '. EZ 100966ASAR rpt ATC Associates Inc \\San Diego\EZ Serve\100966\Reports\100966SAR001 rpt ATC Project No 43 25827 0026 2