ARCHIVED REPORTS XR0013107 - Laserfiche WebLink

Home Browse Search

6. beneath the suspected diesel pipeline leak near 125 Sixth Street contains petroleum hydrocarbons. The results of the soil samples are summarized as follows: • TPH as diesel was detected in samples from 4.5 to 5.5 feet bgs at locations E, F and 10 at 760 ppm, 620 ppm, and 7.5 ppm, respectively; f • Sample location G did not contain detectable TPH concentrations at 5 feet bgs but the 14.5 and 20 foot bgs samples contained TPH diesel levels of 21,000 ppm and 6,700 to 7,700 ppm (duplicate analyses), respectively; • None of the samples contained detectable levels of TPH as gasoline; . Benzene was detected at 0.2$ m and 0.68 m at sample locations E and F, �,. • PP PP P respectively; and ,. Sample Locations E, F, and G contained ethyl benzene (0.1 to 1.5 ppm) and total xylenes (0.4 to 11 ppm). Toluene was detected at 0.94 ppm at location F. L 5.0 SITE VISIT L During the site visit by USPCI, no obstructions to conducting the soil gas survey or drilling along the length of the pipeline were observed. Connections for a water supply to rinse the line and collect the rinsate were investigated and found. However, recent utility construction (storm drain) at the intersection of 8' and Fresno may have cut the diesel pipeline. It is F unknown if the line was repaired or if it was damaged during construction activities in this area. If the line is damaged, alternative methods to rinse the line will be investigated. Regardless, the line will be pressure tested with air to determine if any leaks exist prior to flushing the line. i1.. 6,0 DATA INTERPRETATION AND RECOMMENDATIONS 6,1 Data Interpretation The presence of petroleum hydrocarbons was detected by the soil gas survey and confirmed by the soil samples in the vicinity of the suspected leak at 125 Sixth Street. The lateral extent of petroleum hydrocarbons in the soil along the pipeline appears to have been defined. 6d The vertical extent, however, has not been defined because duplicate samples at location G indicate TPH diesel concentrations of 6,700 to 7,700 ppm at 20 feet bgs, the deepest sample taken. w The soil gas survey primarily detected petroleum hydrocarbons in the carbon 4 to carbon 9 range, whereas the soil samples indicated that the soil contamination is comprised of diesel components. Diesel typically consists of predominately carbon 8 and above hydrocarbon compounds, although diesel does contain lighter fraction hydrocarbons. These results suggest `, fAeAk3T0CKT0N.SG 5