Laserfiche WebLink
5 0 CONCLUSIONS AND RECOMMENDATIONS <br /> 1 <br /> 5 1 CONCLUSIONS <br /> Distribution of TPH in Soils <br /> • Reported concentrations of TPH varied from <5 to 2,800 mg/kg in all soil samples, <br /> • The highest reported concentrations of TPH were observed from 21 to 26 feet bgs <br /> at 1,900 and 2,800 mg/kg, <br /> • The highest reported concentration of TPH below 31 feet bgs was 18 mg/kg, <br /> + There were no reported detections below 36 feet bgs <br /> IN. The sharp decline in TPH concentration with depth suggests that the site is retaining TPH-d <br /> in the unsaturated zone, approximately 30 feet above the groundwater table (56 feet bgs) <br /> P. There were no reported detections of volatile halogenated hydrocarbons from any soil sample <br /> Potential Mobility of Hydrocarbon Compounds <br />. • Analyses for total naphthalene, dibenzofuran, and 2-methyl-naphthalene were <br /> reported at concentrations varying from 0 22 to 14 mg/kg in samples with TPH-d <br /> concentrations of 1900 and 2800 mg/kg, <br /> • NaphthaIene, the most potentially mobile constituent of diesel oil, was the only semi- <br /> volatile constituent reported in WET extract samples, <br /> • Reported concentrations of total TPH-d exceeded WET extractable TPH-d by a factor <br /> of 368 to 1267 indicating the water solubility of TPH-d is very low, <br /> • Reported concentrations of total naphthalene exceeded WET extractable naphthalene <br /> by a factor of 36 to 65, <br /> • Total concentration of napthalene was very low, less than 5 mg/kg in the most <br /> highly impacted soil samples <br /> ► Based on the soluble total and WET extractable analyses, only a small portion of TPH-d or <br /> naphthalene is water soluble and likely to be mobile in soils, <br /> Designated Level Methodology Evaluation <br /> • No state or federal water quality goal has been developed for TPH-d, therefore the <br /> risk-based SNARL value of 0 1 mg/l was used, <br /> SAC 156 14 13 <br /> DAMES & MOORE <br />