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FILE NO. 20-3978-01.WR6 k`■ KLEINFELDER FEBRUARY 24, 1997 mg/L. Based on Kleinfelder's experience the metals concentrations detected in samples from borings 6-1 through 6-7 and 6-9 through 6-27 are indicative of naturally occurring background levels. The concentration of soluble lead present in the soil sample obtained boring 6-8 at a depth of 0.5 feet does appear to be indicative of a spill or release of some type. 6.2.3 Hydrocarbon Concentrations in Soil The only petroleum hydrocarbons detected were unidentified extractable compounds with not less than 14 carbon chains. These were detected in all but five(5) of the samples analyzed. Of these, all of the "non-detects" but one were samples taken at a depth of five feet. Detectable quantities of the organochlorine pesticides 4,4'-DDE and/or 4,4'-DDT were found in four (4) surface samples (sample locations 6-7, 6-13, 6-14, and 6-15). Detectable quantities of the chlorinated herbicides 2,4-D and/or 2,4-DB were found in six (6) surface samples (sample locations 6-6, 6-9, 6-13, 6-14, 6-15 and 6-18). No semi-volatile organics were detected using the EPA Method 8270 other than those tentatively identified compounds (TICS) found using the GC/MS "open scan." Of those detections, only cyclohexanone, heptacosane, heptadecane, 9- octyl, and several unknowns were detected in more than one sample. Two method blanks were also run for EPA Methods 8080, 8150 and 8270 on January 15, 1997 and January 28, 1997. Both of these samples yielded no detection for EPA Methods 8080 and 8150; however, the EPA Method 8270 results showed detection of the two (2) most frequently occurring TICS above, cyclohexanone and unknowns. 6.2.3.1 PRGs Versus Detected Compounds The results of the pesticide and herbicide analyses were compared to the U.S. EPA Preliminary Remediation Goals (PRGs) for residential sites. Residential PRGs were selected for comparison due to the proposed use of the site and the proximity of residences adjacent and west of Powers Avenue. PRGs are contaminant concentrations in,environmental media (i.e. soil, air, water), calculated by the U.S. EPA, that can be used as screening tools to evaluate a site for potential human health risks. PRGs are calculated using standard assumptions and are specific for land use conditions (e.g. residential or industrial). The chemical concentrations calculated by the U.S. EPA typically correspond to a fixed level of risk(usually 10-6, or 1 in 1,000,000 cancer risk, or a non-cancer hazard quotient of 1) for soil, air, and water. The following exposure pathways were accounted for in the PRG calculation for soils assuming industrial land use: • Ingestion • Inhalation of particulates Inhalation of volatiles • Dermal (skin) absorption 20.3978-ol.WR61207RE074.doc Page 14 of 17 0/997, Kleinfelder,Inc.