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5 t " I IVULEM A,susMEN r s1UMT INUU0,140 QUAHTEMY MoW o(%NQ MIM 1399 East YpSemda Avenue,Martlaca.Cnide,nia .�. The site lies approximately 41 feet above mean sea level (MSL.). 'topographic relief at the site is minimal;the ground surface slopes gently to the southwest. The site is paved with asphalt, except in the area of the pump islands and the USts, where the surface is concrete. Six wells (domestic, municipal, and irrigation) are located within a 1-mile-radius of the site. A discussion of the wells and their locations is presented in a report by a previous consultant �. (Delta, 1939). 2.2 Rdlacent land Uses The site is located in a commercial area of eastern Manteca. The property is bounded on the north by a small shopping center, on the west by a fast food restaurant, on the south by East Yosemite Avenue and on the east by Northwoods Drive. 2.3 Spill and Investigation History There has been no documented release of petroleum hydrocarbons at the site. Observation of the former USTs during an epoxy-lining procedure in 1985 indicated that no holes were present. 2.4 Previous Investigations w Aegis assumed responsibility for the site investigation in January 1991. Work performed at the site by previous consultants included investigations by ETS, Delta, and NGA. The results Of laboratory analysia of soil and groundwater from these investigations are summarized in a Table 2 (Analytical Results: Soil Borings), Table 3 (Analytical Results: Groundwater), and Table 4 (Analytical Results: Soil Samples and Soil Borings During Tank Excavation). The laboratory reports are included in Appendix C. 2.4.1 Earth Treatment Systems Four soil borings (SB-1 through SB-4)were drilled by ETS in August 1988. Soil boring SB-4 was converted to a monitoring well (MW-1). SB-1 was drilled to a total depth of 23 feet, SB-2 to a depth of 25 feet, and SB-3 to a depth of 10 feet. MW-1 was completes' as a 2-inch- diameter well to an approximate depth of 361h feet. Approximate locations of the soil borings and the monitoring well are shown on Figure 2. 10, 15, and 20 feet in SB-1, SB-2, and MW-1. A Samples were obtained at depths of 5, 10-foot sample was collected from SB-3. Soil samples from the borings were analyzed for BTEX, EDC, EDB, and TPH, as gasoline. Toluene ranged from 0.006 to 0.013 ppm in SB-1 and from 0.006 to 0.064 ppm in SB-2. Maximum concentrations of BTEX and TPH in the soil. samples from MW-1 were 0.05, 0.03, 0.42, 1.6, and 28 ppm, respectively (Table 2). 3 F �