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SAFEWAY MEAT PACKING FACILITY, STOCKTON, CALIFORNIA <br /> TIER II RisK BASED CORRECTIVE ACTION <br /> FEBRUARY 26, 1996 <br /> PAGE 2 - 3 <br /> 2.2 TPH Results and Composition of Diesel Fuel <br /> Detecting TPH-D in a sample without finding detectable concentrations of BTEX and/or PAH <br /> constituents is not necessarily indicative of a threat to human health or groundwater quality <br /> TPH-D is a screening level analysis that measures all hydrocarbons that have carbon chain lengths <br /> between approximately C-10 and C-20 Not all chemicals or materials measured and reported <br /> as TPH-D are diesel fuel residuals As diesel weathers in the environment, it develops a <br /> characteristic chromatographic pattern (Bruya, 1993) The analytical laboratory that conducted <br /> the latest soil TPH-D analyses for the Stockton site indicated that the chromatographic patterns <br /> for TPH-D in the soil at the Stockton site do not match the pattern seen with weathered diesel <br /> in soil (Krazen 1995) Other potential sources of semivolatile hydrocarbons in the subsurface <br /> soils include the wastewater pipes within Navy Drive south of the facility <br /> Analytical testing of the soil and groundwater at the Stockton facility have included testing the <br /> soil and groundwater for the most toxic constituents of diesel that is, the BTEX and polycyclic <br /> aromatic hydrocarbons Concentrations of BTEX and the larger PAHs (i e , the PAHs with four <br /> to six ring are potentially carcinogenic) in the soil and/or groundwater are very low, even when <br /> the concentration of TPH is greater than 1,000 mg/kg (or 1,000 ppm) in soil These results are <br /> consistent with the composition of virgin diesel fuel <br /> Diesel fuel is the distillation fraction of petroleum crude that boils from approximately 160°C to <br /> 400°C It is a complex mixture of aliphatic and aromatic hydrocarbons that range in carbon-chain <br /> length from C-10 to approximately C-24 (The range of carbon compounds defined as diesel can <br /> differ slightly from the range measured in TPH-diesel analysis ) It contains approximately 30% <br /> to 40%monocyclic and polycyclic aromatic hydrocarbons (PAHs) and 60 to 70% straight-chained <br /> and branched alkanes The concentrations of the smaller, noncaremogenic PAHs (e g , <br /> Q131cDJ1 <br />