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26 September 1997 AGE-NC Project No 97-0330 Page 6 of 7 20 feet bsg and from P-2 at depths of 25 and 35 feet bsg Reduced concentrations of TPH-d were detected in samples from P-2 at 45 and 50 feet bsg and from P-4 at 25 feet Therefore, it appears that soil impacted by TPH-d in the UST area may be limited in vertical extent to estimated depths of 50 feet bsg • Concentrations of toluene, ethylbenzene and xylenes were detected in soil samples P 1-20, P2- 35 and SP1-3 at concentrations up to 0 017 ppm, 0 11 ppm and 0 52 ppm, respectively However, the detections of toluene, ethylbenzene and xylenes were below the State of California Maximum Contaminant Levels (MCLs) for drinking water of 150 ppb, 700 ppb and 1750 ppb, respectively A summary of the California Drinking Water Standards is contained in Appendix D • The polynuclear aromatic hydrocarbons fluorene, naphthalene and phenanthrene were detected in a composite soil spoils pile sample at concentrations of 1,400 parts per billion (ppb, reported as micrograms per kilogram), 1,600 ppb and 2,400 ppb, respectively The concentrations of naphthalene and fluorene are well below 240 ppm and 90 ppm, the levels set by the EPA's Preliminary Remediation Goals for Planning Purposes, dated 01 August 1996 Fluorene, phenanthrene and naphthalene are not regulated chemicals in the California Drinking Water Standards • Organic vapor and hydrocarbon odor were not detected in soil sample duplicates collected from soil boring P-4 • Laboratory data suggests that the greatest magnitude of petroleum hydrocarbon impact occurs near P-2, advanced near the reported former product line Figure 3 depicts the estimated lower vertical and horizontal extent of the hydrocarbon-impacted soil in the drilled portion of the site • Ground water was encountered at a depth of approximately 62 feet bsg during advancement of soil borings P-3 and P-4 (Appendix A) • Analytical results of ground water samples collected from soil borings P-3 and P-4 detected TPH-d concentrations at 510 and 70 gg/l The Central Valley Regional Water Quality Control Board has declared enforceable limits for TPH-d based on the USEPA "Suggested No Adverse Response Level (SNARL)" of 100 ggll • A mass-volume calculation of impacted soil beneath the former UST and dispenser area, assuming an even, radial distribution of hydrocarbons, yields an estimated 3,166 gallons of Advanced GeoEnvironmental,Inc