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1 <br /> File No. 249947 ' 20 May 1991 Page 9 <br /> ' TABLE 3. RESULTS OF LABORATORY ANALYSES FOR VOLATILE ORGANIC CONST11I - M <br /> SAMPLE <br /> ' NUMBER Benzene(ppb) Toluene(ppb) Ethylbenzene(ppb) Xylenes (ppb) <br /> S-1 ND 6.5 ND ND <br /> S-2 ND ND ND ND <br /> S-3 ND ND ND ND <br /> S-4 ND 14.0 ND ND <br /> S-7 N D 5.4 N D N D <br /> I <br /> ABBREVIATION: -� ' ,(r <br /> ppb : pans per million (or ug/kg). <br /> ' N D : substance(s) not detected in laboratory analyses. <br /> DETECTION LIMITS: <br /> ' 5 ppb, all constituents <br /> 2.4 Discussion of Results <br /> ' We did not encounter any evidence of petroleum-based contamination in the areas <br /> excavated during this investigation. Our field observations are supported by the fact <br /> ' that no total petroleum hydrocarbons were detected in the samples submitted for <br /> analyses. <br /> ' Low levels of toluene were detected in three of the samples analyzed in this <br /> investigation. Toluene is an industrial solvent used in the manufacture of medicines, <br /> perfumes, and dyes, and also as a gasoline additive. However, because no other <br /> ' contaminants were detected in the five samples, we have reason to question the <br /> existence of toluene in the samples from these locations. <br /> ' The Environmental Protection Agency (EPA) has recognized toluene to be a <br /> laboratory contaminant; because of flaws in the design of standardized analytical <br /> procedures, this chemical (and others) has been erroneously detected in controlled <br /> ' experiments. EPA guidelines suggest that levels of toluene falling at or below ten <br /> times the test detection limit (or, in this case, 50 ppb), can be discounted as <br /> laboratory contamination. This would account for the contamination levels in the <br /> three samples results. <br /> The Maximum Contaminant Level (MCL) for toluene in drinking water is 2000 ppb <br /> (2 ppm). It is generally accepted that groundwater flushed through contaminated <br /> ' soil will contain concentrations of contaminants which are far less than those found <br /> in the soil; thus, soil containing less than 2 ppm of toluene probably would not <br /> present a threat to area groundwater. The levels of toluene detected in the soil <br /> samples are over one hundred times less than this level. <br /> 1 <br /> ANDERSGN <br /> ' GGNSIILTING <br /> GRGt1P <br /> 0 <br />