ARCHIVED REPORTS XR0013014 - Laserfiche WebLink

Home Browse Search

595 F. i 10'St., Tracy scavengers 1,2-DCA and EDB. "lhe testing was conducted using modified EFA Method TO-15 GUMS. Upon receipt of the vapor analysis data we prepared a summary table and evaluated the measurements with respect to general, conservative risk-based screening levels set forth by the SFBRWQCB (February 2005 ESLs, Table E-2), The primary comparison was with screening levels for residential exposure since that is the Site's predominant.land use, but commercial ESLs were also included. Finally, we prepared this written report documenting the work performe md, the findings gained and our conunents and recommendations, FINDINGS AND COMMEN'T'S Field Iogs of the five holes are presented in Appendix C. Physical property test results are summarized in Table I and presented in their entirety in Appendix D. The area of SV-1 closest to the former USTs has gravel baserock surfacing; the other explored areas amongst the trailer homes tend to be bare soil. Consistent with prior rounds of site exploration, the encountered native soils within the upper 5 feet penetrated for this work are silty clays with rap to 28% total of sand and gravel. The two grain size tests confirm field observations. Porosities, bulk densities, and total organic carbon (TOC) amounts were comparable to typical values for such soils. No ground water was encountered during boring advancement. The soil seemed primarily damp based on field impressions, with generally increasing moisture with depth. The two lab tests measured moisture contents of 15%and t 7%. No fuel odors were apparent in any of the augered holes or removed soils. '17he analytical soil vapor data are summarized in Table 2 and presented in their entirety in .Appendix E. Also included in Table 2 are the shallow soil gas screening levels for potential vapor intrusion concerns (ESLs for both residential and commercial) for the target constituents. ESLs for three of the oxygenates (EtBE, DIPS and TAME) have not been published, but none of these compounds were detected. The highest soil vapor concentrations were found at .Location SV-1 and SV-5, with SV-1 having slightly higher TPHg and SV-5 having slightly higher TEX. Toluene and xylenes were found in all vapor samples, but benzene was not detected in any. Concentrations of all constituents were at least an order of magnitude below the residential ESLs, and most measurements were several orders below those thresholds of concern. RECOMMENDATIONS Based on the outcome of the subject soil vapor assessment, which conservatively targeted the known areas of highest fuel residuals, it is apparent that site conditions do not present a vapor intrusion risk or hazard, even for residential land use. Accordingly, it is Wright's recommendation that EHD proceed with granting this case no.further action required (NFAR) status. LIMITATIONS This report and the associated work have been provided in accordance with the general principles and practices currently employed locally in the environmental consulting profession. This is in lieu of all warranties, express or implied. Wright Environmental Services Page 3 of 4 lune 4,2007