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I.r fir/ ago. The UST was removed in early 2002. Petroleum hydrocarbon analytes were not detected in 4 a soil sample collected from the base of the UST excavation(IT, 2002a). Soil sample analytical data is included in Table 1 and depicted in Figure 3. In March 2002, a 2,000-gallon diesel UST was removed from another area of the site. The tank had contained fuel for an emergency backup power generator. During removal activities, groundwater was encountered at a depth of approximately 12 feet bsg. A soil sample collected L" from the north end of the excavation contained 1.3 parts per million(ppm) of total petroleum hydrocarbons as diesel (TPH-D), and a sample collected from the pipeline trench contained L. 5.0 ppm TPH-D. A groundwater sample collected from the excavation contained 130 parts per billion(ppb) of TPH-D (IT, 2002b). Soil sample analytical data is included in Table 2 and depicted in Figure 3. Groundwater sample analytical data is included in Table 3 and depicted in Figure 4. V In September 2002,at the request of the SJCEHD, six direct-push soil borings were performed adjacent to the former 2,000-gallon diesel UST location to attempt to ascertain the extent of soil V and groundwater impact in the area. Analysis of the soil samples detected TPH-D in one of the borings at a concentration of 2.7 ppm. No benzene, toluene, ethylbenzene, and xylenes (BTEX) constituents or methyl tertiary butyl ether(MTBE) were detected in any of the soil samples (IT, 2002c). Soil sample analytical results are included in Table 4 and depicted in Figure 5. V Groundwater was encountered during boring activities at depths ranging from 11 feet to 14 feet t.. bsg. Analysis of groundwater samples collected from three of the borings detected TPH-D at concentrations ranging from 50 ppb to 390 ppb. No BTEX constituents or MTBE were detected in the samples. Table 5 summarizes the laboratory analytical data. Figure 6 depicts the groundwater sample analytical results. V In April 2003, a site conceptual model (SCM) was completed for the site by Shaw. The results of the SCM have indicated numerous UST systems have historically been located on nearby properties. The majority of these UST systems were located to the south, in the anticipated upgradient direction, with several of the UST systems reporting leaks upon removal. Based on LO the data, it is surmised that contaminants from these former UST systems may have impacted underlying groundwater conditions at the SBC site (Shaw, 2003). CNCD\04-28/03\SHARE\USlF\03-0027.doc 2 V V