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mW3 Ogg SON • a'a Itis Aromatic Hydrocarbons All Ihree groundwater samples collected were analyzed for aromatic hydrocarbons. No aromatic hydrocarbons were detected in these samples. Fecal Coiltorm. Fecal Coliform: bacteria were not detected in any of the samples submitted (Table 3). REGULATORY ASSESSMENT In California, impacts of contamination to the environment by TPHD and BTEX are evaluated on a case-by-case basis. None of the compounds detected have a Total Threshold Limit Concentration (TTLC) and/or Soluble Threshold Limit Concentation $TLC ( ) value reported in Title 26, California Code of Regulations, �. Division 22,Section 66680. w• The RWQCB uses I00;ng/kg TPH as a minimum criteria in soil samples for characterization of groundwater in leaking underground fuel tank cases. The DHS use: 1,000 mg/kg as a rnirimum criteria for remediation. One thousand mg/kg - TPH is considered hazardous by virtue of its potential ignitability. ?Many Ioca! (implementing agencies (LI,Ats), surra as SJCPHS/EHD, use the LUFT Manual (1989) as guidance in the assessment and cleanup of UFST sites. The LUFT Manual recognizes three site investigation categories: Category 1, no evidence of soil contamination; Category 2,known soil contamination; and Category 3, known or suspected groundwater pollution. Analytical resu;ts for soil samples obtained during the removal of the UFSTs (Groundwater Technology, 1991) and this investigation indicate the site can be classifiedunder Category 2 (kno - soil contamination). A leaching potential analysis fcr diesel (Table 2-2, LUFT Manual) was performed for the sample collected from B-1 at a depth of 25.0-26.5 feet below -,� ground rurface. This sample contained 6,800 mo/kg TPHD and 0.600 mg/kg ethylbenzene. According to the leaching potential analysis (Appendix Ds the maximum allowable TPH levels that may be left in the subsurface is I00 mg/kg The general risk assessment criteria (Tables 2-2 and 2-3, LUFT Manual) indicates that the following concentrations of aromatic hydrocarbons are acceptable contamination levels (pollutant mass accumulations) for protection of groundwater at qualified sites: benzene 0 1 lone 20 ( PPM); toluene (6 ppm); ethylbenzene (30 ppm); and xylene ( ppm). These levels were calculated using Tables 2-4 through 2-7 in the LUFT Manual and the following assumptions: average annual precipitation (14.1 ^ inches) (NOAH, I991); depth to groundwater (43.5 feet); distance from sample to surface (25.0 feet); and distance from sample to ;groundwater (18.5 feet), The BTEX concentrations in Sample 13-1 are non-detect (benzene, toluene, xylene) and 0.600 ppm (ethylbenzene). Thus, BTEX levels are below acceptable contamination levels. 6 IAL/SY132.21/o083 REV 0