ARCHIVED REPORTS_XR0012641 - Laserfiche WebLink

Home Browse Search

.t4 i x end point soil samples showed up to 6,900 ppm p500 total 56 petroleum hydrocarbons (TPH), PP benzene, PPm toluene, 140 ppm ethylbenzene, 770 ppm xylenes, and 0.8 PPM organic lead. According to McClaren (Appendix I, page 5) -these samples were collected at approximately 17 feet beljw grade within the capillary fringe. The capillary fringe is a tension saturated zone above the standing water table. A grab sample of water from the excavation showed TPHG and BTEX levels comparable to the soil sample results. The total excavated area is shown on page 14 of Appendix I. An estimated 45 cubic yerds of contaminated soil were excavated. This soil was stockpiled at the site and later aerated in accordance with the San Joaquin Local Health District approved soil remediation work plan of December 7, 1988 and the January 19, 1989 and March 2, 1989 amendments to the soil remediation workplan. Aeration was performed at two locations (designated Aeration Pile 1 and Aeration Pile 2) at the Woodbridge Cellars facility. Samples were collected from Aeration Pile 1 on May 25, 1989, composited, d submitted for analysis of total petroleum hydrocarbons, specifically gasoline (TPH/G) and benzene, an toluene, xylenes, and ethylbenzene (BTEX) . Similarly, samples were collected from Aeration Pile 2 on July 27, 1989, composited and submitted for analysis of total volatile hydrocarbons (TVH) and BTEX. The analytical results are presented on Table I. No further soil excavation or aeration has been performed at the site. 4.2 Additional Proposed Soil Remediation Six soil borings have been sampled immediately adjacent to the former tank pit (Soil Borings 1-5 and monitoring well 1)_ Soil samples from each of the borings at approximately 14 to 17 feet below grade were subjected to laboratory analysis for gasoline hydrocarbons. None of these samples recorded BTEX above the Regional Water Quality Control Board typical designated levels for these constituents_ Benzene was below detection limits for all samples analyzed. Undifferentiated gasoline hydrocarbons (TPHG) were present only in borings MWI, SBI, SB2 and SB5 at levels ranging from 47 to 790 ppm. These soil boring samples contrast with the samples taken from directly beneath the former pit at approximately 17 feet (Appendix I, page 7) which showed very high levels of both undifferentiated gasoline hydrocarbons (to 6900 ppm) and BTEX (to 1427 ppm). This data strongly suggests that hydrocarbons released from the former tank at the site migrated dominantly in the vertical direction until reaching, -. ----the-water-table and-that -there after....spreading._.was controlled by groundwater movement. 3