Laserfiche WebLink
595 E. 1 l Ih St.,'Tracy <br /> Replacement monitoring wells in the core impact area have demonstrated a significant <br /> improvement in groundwater duality and the fuel leak case is now recognized as a justifiable <br /> candidate:for no further action, subject to 11-ID's review of the subject vapor study. <br /> The main objective of the subject soil vapor assessment was to evaluate the areas of highest <br /> residual fuel impacts, particularly those within the mobile home park portion of the Site, to see if <br /> there is any significant potential health hazard or risk. As discussed later herein, the measured <br /> concentrations were compared to the generic vapor-based FSLs published by the San Francisco <br /> Bay Regional Water Quality Control Board (SF)3RWQCB) and found to be well below those <br /> conservative thresholds. <br /> SUMMARY SOF WORK PERFORMED <br /> This section provides a summary of the work tasks performed for the subject soil vapor <br /> assessment. More detailed procedures are provided in Appendix B. <br /> On May 1, 2007 small (3 1/-inch) diameter holes were opened to a nominal depth of five feet at <br /> the five approved sampling locations (see SV-1 through SV-5 on Figure .1) usic�g pre-clean <br /> nent. Representative soil cores were obtained from the vapor sampling <br /> hand-auger eguip2 <br /> intervals in order, to conduct physical property testing (see description below). Soil conditions <br /> were logged by a Professional Geologist. Due to the clayey nature of the soil, TIO significant <br /> sidewall caving occurred. Temporary vapor sampling points were constructed in the holes as <br /> fdescribed in Appendix B. The '/4-inch(OD) tubing eananating from each temporary well location <br /> was sealed with avapor-tight valve and secured in preparation for sainplzng tl e ollowing day. <br /> On May 2, 2007 vapor samples were collected from the five points by an experienced specialist <br /> from Toxichem following the protocols presented in Appendix B. The procedures cover the <br /> steps used to verify that no significant leaks were present and to purge the system before sample <br /> collection in laboratory-supplied, evacuated Summa canisters, One QA/QC duplicate sample <br /> was collected from the group, specifically from SV-4. No problems occurred during the <br /> sampling process. Field notes are provided in Appendix C. After receipt of the laboratory data <br /> that showed no re-sampling was warranted., the temporary installations were removed and the <br /> small retrieval holes sealed with hydrated bentonite to EHD satisfaction. <br /> Soil samples from all five holes were submitted to McCampbell Analytical, a state-certified <br /> laboratory in Pittsburg, with instructions on the chain-of-custody record to test SV-4 and SV-5 <br /> (deemed representative of the study area) for bulk density, Porosity, moisture content <br /> , grain size <br /> distribution (subcontracted to Cooper Testing Laboratory) and total organic carbon (TOC). The <br /> testing was conducted using established methods (e.g., SSSA #5, API 40RP, ASTM 2216, <br /> ASTM D422 acid SM531 OB). <br /> The six vapor samples (five plus the duplicate) were submitted along with chain-of-custody <br /> documentation to Air Toxics Ltd, a state-certified laboratory in Folsom. In accordance with <br /> EHD comments to our Work plan, the vapor samples were analyzed for total petroleum <br /> hydrocarbons as gasoline; (TPHg); the four main aromatic compounds --- benzene, toluene, <br /> ethylbenzene and xylenes (BTEX); oxygenates MtBE, TBA, EtBE, RIPE and TAME; plus lead <br /> Wright Cnvironmental services .Page 2 of 4 <br /> June 4,2007 <br />