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' 3.2.2 Subsurface Investigations g s ' In August and September 1990, a subsurface environmental investigation was conducted by USTEC (USTEC, November 1990) A total of thirteen soil borings (B-1 through B-13) were drilled The locations of the soil bonngs are shown on Figure 3 The bonngs were drilled to depths ranging from 70 to 95 feet below ground surface Boring construction details are presented in tables included in Appendix A 1 Fifty-two soil samples were collected and submitted for laboratory analysis The results of laboratory analyses are summarized in Tables 1 and 2 TPHg concentrations in soil ranged from nondetectable to 8,900 ppm TPHd ranged from nondetectable to 20,000 ppm BTEX ranged from nondetectable to 920 ppm (the highest being total xylenes) The highest petroleum hydrocarbon concentrations were detected in boring B-5 at a depth of 20 feet, located immediately north of the former gasoline UST Organic lead, a constituent of leaded ' gasoline, was nondetectable in all samples except one where it was detected at 0 059 ppm in boring B-5 at a depth of 20 feet (Table 2) The majority of petroleum hydrocarbons were present from ground surface to about 25 feet below grade, and within a radius of approximately 25 feet from the former tank pit The extent of TPHg in soil beneath the site is depicted on Figure 4 In addition, BTEX and TPHd soil concentration contours are presented on figures prepared by USTEC contained in Appendix E ' Polynuclear aromatic hydrocarbons (PNAs) were also analyzed, and results are summarized in Table 2 PNAs were nondetectable in all samples, with the exception of naphthalene in boring B-1 at 10 feet and 15 feet (30 ppm and 32 ppm respectively), in boring B-3 at five feet (3 3 ppm), and, in boring B-5 at 20 feet (54 ppm) PNAs are not currently regulated in soil or ' water, but are regulated in air ' Under the supervision of USTEC, eleven additional step out borings (B-14 through B-24) were drilled in October and November 1990 (Figure 3) Cumulative results of laboratory analyses ' of soil samples are summarized in Tables 1 and 2 TPHg was nondetectable in all eleven bonngs, with the exception of borings B-15 and B-16 TPHg in these two borings ranged from nondetectable to 630 ppm (at 5 feet in B-16) TPHd was nondetectable in all borings except B-14 through B-17, and ranged from nondetectable to 50 ppm (in boring B-16 at 15 n 1054006%reports1CL01195 doe 4 • SMTH