ARCHIVED REPORTS XR0000855 - Laserfiche WebLink

Home Browse Search

' 4 FIELD INVESTIGATION ' 4.1 Soil Boring and Sampling Between August 28 and September 7, 1995, an EMCON geologist observed Woodward Drilling (Woodward) of Rio Vista, California, drill six vertical soil borings (B-1, B-3 through B-5, B-7, and B-8) and two 45 degree angle borings (B-2 and B-6). Three of the ' borings (B-1, B-4, and B-5) were converted to groundwater monitoring wells (MW-1 through MW-3), and three of the borings (B-3, B-7, and B-8) were converted to duel- completion vapor extraction wells (VW-1 through VW-3). Borings were located to ' evaluate residual hydrocarbons in soil near the USTs and dispenser islands and dissolved hydrocarbons in groundwater beneath the site. Woodward drilled the soil borings using a Mobile B-57 drilling rig. EMCON field procedures are presented in Appendix A. The total depths of the six vertical borings (B-1, B-3 through B-5, B-7, and B-8) ranged from 61.5 to 75.6 feet below ground surface (bgs). Groundwater was first encountered between approximately 58.5 and 61 feet bgs. Borings B-2 and B-6 were drilled at a 45 degree angle to a vertical depth of 25 feet. Groundwater was not encountered in borings B-2, B-6, and B-8. The boring locations are shown on Figure 2. Undisturbed soil samples were collected for classification and laboratory analyses at approximately 5-foot intervals or at soil lithology changes, from the ground surface to the total depth of the borings. The soil samples were classified using visual and manual methods according to the Unified Soil Classification System. During sampling, a flame ' ionization detector (FID) or a photoionization detector (PID) was used to characterize the relative levels of hydrocarbon vapor emitted by soil samples. Readings recorded in the field are shown on the logs of exploratory borings presented in Appendix B. Drill cuttings ' were stored on site and placed on and covered with plastic. On September 7, 1995, a geologist from EMCON collected four soil samples from the ' stockpiled soil to be composited at the laboratory for analyses to evaluate disposal options. At ARCO's request, the drill cuttings were transported by Dillard Trucking of Byron, California, to Browning-Ferris Industries in Livermore, California, for disposal. SAONNPJU0805\08051470.IBS-95\pas:1 Rev.0,216/96 0805-147.01 4-1