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1 <br /> Mr Daniel K Barber,P E <br /> lie September 9,2003 <br /> Page 8 of 17 <br /> rsource area, with the vertical component substantially less The leading edge, or non- <br /> detection line, of the subject property plume could be verified through well-placed <br /> downgradient hydropunch sampling <br /> Site Contaminants of Concern <br /> iPrevious site investigations have quantified petroleum hydrocarbons by three different <br /> analytical methods, which vary (and overlap) in their petroleum compound-specific <br /> 1 quantification <br /> 1 "Total Purgeable Hydrocarbons" — This method quantifies total petroleum ! <br /> hydrocarbons in the carbon chain range of C6 to C12 <br /> 2 "Total Extractable Hydrocarbons as Kerosene" (TEHk) — This method quantifies total <br /> 1 petroleum hydrocarbons in the carbon chain range of C 10 to C16, and quantifies the <br /> mass relative to a kerosene standard <br />' 3 "Total Extractable Hydrocarbons as Diesel" (TEHd) — This method quantifies total <br /> petroleum hydrocarbons in the carbon chain range of C10 to C28, and quantifies the <br /> 1 mass relative to a diesel fuel standard <br /> 4 "Diesel Range Organics" (DRO) — This method quantifies total petroleum <br /> hydrocarbons in the carbon chain range of C10 to C28, and does not quantify the mass <br />' relative to any specific fuel standard <br /> It is our understanding that these methods were employed in previous investigations to <br /> quantify the full range of potential petroleum compounds that might be present, including <br /> gasoline and diesel fuel There is no documentation available as to why TEHk was requested <br /> for quantification, which was conducted in the earliest (1999) subsurface investigation by a <br /> previous consultant <br /> ' For most samples with detectable TEHd, the laboratory reports note that the sample <br /> chromatogram does not match the diesel or kerosene standard chromatogram Our analysis of <br /> ' the available chromatograms indicates that the contamination likely is a weathered (older) <br /> diesel fuel that has lost by volatilization and/or degradation the volatile range (approximately <br /> C10 to C14) This fuel signature does not resemble kerosene Because of the co-elution <br /> ' (chromatogram overlap) of the kerosene and diesel ranges, in our professional opinion, the <br /> reported TEHk contamination is a false-positive (i e , the hydrocarbon range is being "double- <br /> counted" by the two methods), and the appropriate quantification of extractable-range <br /> hydrocarbons is as diesel (TEHd) The sum of the Total Purgeable Hydrocarbons and TEHd <br /> ' concentrations is the most representative value for Total Petroleum Hydrocarbons The <br /> Stellar Environmental Solutions <br /> i PNOlEC�2Wi ncRoynil003�0 AB.ha., •.CbsurnNeyon rn1 FlwNREPORT Sepwber R](q]Jr.c <br />