ARCHIVED REPORTS_XR0002117 - Laserfiche WebLink

Home Browse Search

4.2 Soil Sam le AnalYhcall Results The soil samples collected were submitted under chain-of-custody to Pace Incorporated, of Novato, California, a state-certified analytical laboratory The samples were analyzed ' for a) TPH, as gasoline (TPH-G), by GC-FID/EPA Methods 503018015, and, ' b) benzene toluene e thylbenzene, and total xylenes (BTEX) by EPA Method 8020 ' Laboratory analytical reports indicated petroleum hydrocarbons in two of the borings, SB-8 and SB-9 One sample from SB-8, SB 8-6 at 6 feet, contained detectable ' concentrations of toluene, ethylbenzene, and xylenes of 0 062, 0 0098, and 0 045 ppm, respectively Of the 12 samples collected from SB-9, nine samples contained detectable concentrations of petroleum hydrocarbons (Table 1) The highest concentrations were t found at 21 feet in SB 9-21 No benzene was detected at or above the laboratory detection limits in any of the samples submitted for analysis Petroleum hydrocarbon constituent concentrations were less than 0 5 ppm deeper than 36 feet Figure 4 is a ' distribution map of TPH-G in soil Laboratory quality assurance and control is addressed in the Aegis SOP included in ' Appendix A The analytical laboratory reports and chain-of-custody forms are included in Appendix C 5 0 GROUNDWATER MONITORING ' 5 1 Groundwater Levels On June 21, 1993, Aegis personnel collected depth-to-groundwater measurements in ' wells MW-1 , MW-2, MW-5, MW-6, and MW-8, prior to purging and sampling Wells MW- 3, MW-4, and MW-7 could not be located Since September 1992, the average groundwater elevation has increased 528 feet in those wells monitored during the ' September 1992 and July 1993 monitoring event (MW-1, MW-2, MW-6, and MW-8) On the basis of the June 21, 1993, measurements, groundwater is estimated to flow to the south-southeast at an average gradient of 0 001 ft/ft Figure 5 is a potentiometric surface Imap of the shallow water-bearing zone on June 21 , 1993 Historically, the gradient has been typically northeast or east Recent and previous groundwater levels are summarized in Table 2 A hydrograph summarizing groundwater elevations since 1991 is included as Figure 6 All groundwater I elevation measurements were conducted according to the Aegis SOP included in Appendix A 93 0058 OMR 3 I