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I <br /> WESTERN 1386 FAST BEAMER STRLFT <br /> .. GEO-ENGfNEERS WOODLAND CA 95776-6003 <br /> (530) 668-5300, <br /> CALIF CONI RAC I OR#513857 FAX(530)662-0273 <br /> REGIS"I LRED GEOLOGISTS %vcgc@mother Lotti <br /> - <br /> �V <br /> December 16, 1998 Fir_ <br /> Mr John Margowski <br /> Wickland I'toperties <br /> P O Box 13648 <br /> Sacramento, California 95853-4648 <br /> (916) 978-2485, FAX (916) 978-2428 <br /> RE REQUEST FOR SITE CLOSURE and Update Status Report #54, November 1998 <br /> Quarterly for former Regal Station #603, 6425 Pacific Avenue, Stockton, California <br /> Dear Mr Margowski <br /> INTRODUCTION <br /> This update, STATUS REPORT #54, presents data collected from September 30, through <br /> December 10, 1998 and includes the Quarterly Groundwater Sampling, Vapor Extraction System <br /> Monitoring and Venting of MW8 Also included with this report is the THIRD REQUEST FOR <br /> SITE CLOSURE as outlined in Appendix B of TRI-REGIONAL BOARD STAFF <br /> RECOMMENDATIONS FOR PRELIMINARY INVESTIGATION AND EVALUATION OF <br /> UNDERGROUND TANK SITES, March 1, 1994. <br /> Site Closure was initially requested in Update Status Report #52 dated July 9, 1998. Using a <br /> Risk Base Corrective Action Tier 11 model benzene needed to be reduced to below 10 ug/L. <br /> This latest sample results shows that benzene levels have been reduced to below 10 ug/L in <br /> wells MW 1, MW2, MW8, MW12, and MW 13. All other wells show benzene to be below <br /> laboratory lower detection limits of 0.5 ug/L. A previous report (CONFIRMATION OF THE <br /> EFFECTS OF THE VAPOR EXTRACTION SYSTEM, for this site, dated July 31, 1997) <br /> documented our findings from the soil boring samples obtained to confirm the effectiveness of the <br /> operating Vapor Extraction System (VES) Drilling/sampling occurred on June 4 and 5, 1997 Four <br /> borings (SB4, S135, S136 and S137) were drilled and sampled Soil sample results from these boring <br /> showed a complete removal of Benzene and Toluene, better than 97% reduction in TPHg and better <br /> than 90% reduction in Xylenes One of these borings (S137) was converted into a two inch vapor <br /> extraction/sparging well and renamed MW 13 Testing for the bio-receptors Dissolved Oxygen (02), <br /> Sulfate (SOA Nitrate (NO3) and Ferrous Iron (Fe2) was performed during the December 1997 <br /> quarterly sampling That report documents the ongoing effects of natural attenuation on the <br /> hydrocarbon plume, showing plume reduction and stability As requested by San Joaquin County <br /> . Health the Oxygenants were sampled for all wells during the December 1997 sampling All wells <br /> were below the laboratory lower detection limits with the exception of MW11, which contained 30 <br /> 1 R643 Update 954/CLOSURE 3 12/98 <br />