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t r Project No 034-98081 J Page No 6 ` nzene concentration (sample 234W) as determined by the gas chromotography (GC) analytical method PA 8021B This sample was also analyzed using GC/mass spectrometer method EPA 8260 to positively identify benzene as the source of the large peak observed on the EPA 8021B chromatogram r Results of the confirmation analysis show the constituent is benzene -- these analytical results are also shown on Table II Copies of GC method chromatograms for the groundwater sample 234W and for the analytical standard APPL, Inc used to quantify TPH-G are presented in Appendix D Review and comparison of the chiomatograms show very dissimilar patterns suggesting the constituents detected in this groundwater sample do not represent gasoline 622 Constituent Relationships Review of the analytical data for both soil and groundwater samples (Tables I and II) shows that the relative ratios of benzene to toluene, ethylbenzene, xylenes and TPH-G are not representative of those commonly associated with either fresh or weathered gasoline For both soil and groundwater matrices, i benzene concentrations greatly exceed concentrations of co-existing toluene, ethylbenzene, and xylenes This relationship was initially alluded to in Kiazan's March 13, 1998 Groundwater Sampling report for the subject site The water sample (P5-W) collected during the investigation summarized in that report contained BTEX and TPH-G at a concentration of 610, 250, 48, 68, and 11,000 gg/l, respectively One of the report conclusions was as follows The concentration ratio of benzene to xylenes in the groundwater sample ten years after UST removal suggests the following 1) biodegradation is not occurring at an optimal rate (due to tight, oxygen poor soil,'), 2) the groundwater sample collected does not represent the core of the groundwater plume, but instead, its periphery, or 3) a combination of not yet understood physical and biogeochemical conditions is controlling contaminant ratios The weighting of constituents toward the lighter PHC fractions (benzene) In the soil and groundwater samples from Krazan's August 1998 investigation is even more pronounced than that noted during Maich 1998 Based on Krazan's experience, the chemical constituent distribution noted in groundwater samples from boreholes B-2 and B-3 clearly is not indicative of gasoline, but, instead, of some other benzene-containing source material This non-gasoline contaminant has been possibly overprinted by niuch lower concentrations of more "typical" gasoline in the immediate vicinity of the former UST KRAZAN & ASSOCIATES, INC Offices Serving the Western United States 3498031 SGS