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WESTERN 1386 EAST BEAMER STREET <br /> '.� GEO-ENGINEERS WOODLAND CA 95776-6003 <br /> (530) 668-5300, <br /> CALIF. CONTRACTOR#513857 FAX(530)662-0273 <br /> REGISTERED GEOLOGISTS wcgc@moiher.com <br /> Mr. John Margowski February- 12, 1998 <br /> Wickland properties <br /> P.O. Box 13648 <br /> Sacramento, California 95853-4648 <br /> (916) 2485, FAX (916) 978-2428 <br /> RE: Update Status Report #50, December 1997 Quarterly Report with results of Oxygenant <br /> analysis and bio-receptors for former Regal Station#603, 6425 Pacific Avenue, Stockton, California. <br /> Dear Mr. Margowski: <br /> INTRODUCTION <br /> This update, STATUS REPORT #50, presents data collected from October 3, to December 22, <br /> 1997 and includes the Quarterly Groundwater Sampling, Vapor Extraction System Monitoring and <br /> Venting of MW8. <br /> • A previous report (CONFIRMATION OF THE EFFECTS OF THE VAPOR EXTRACTION <br /> SYSTEM, for this site, dated July 31, 1997) documented our findings from the soil boring samples <br /> obtained to confirm the effectiveness of the, operating Vapor Extraction System (VES). <br /> Drilling/sampling occurred on June 4 and 5, 1997. Four borings were drilled and sampled. One of <br /> these borings (SB7) was converted into a two inch vapor extraction/sparging well and renamed <br /> MW13. Testing for the bio-receptors Dissolved Oxygen (02), Sulfate (SO4), Nitrate (NO3) and <br /> Ferrous Iron (Fez) was performed during this quarter and further documents the effectiveness of the <br /> vapor extraction system maintaining the aerobic conditions at this site. <br /> PROBLEMS WITH WELL PURGING/SAMPLING PUMP <br /> In the past monitor wells MW4, MWS, MW6, MW7, MW9 and MW 11 have shown to be below <br /> laboratory lower detection limits for the compounds of interest (TPHg, BTEX). During this <br /> sampling round low levels of these compounds were found in all wells associated with the site. <br /> Sampling procedures were changed for this'round in order to obtain representative Dissolved <br /> Oxygen samples. Analytical results of the final pump rinse water indicates that elevated <br /> concentrations of TPHg and BTEX in all wells may have resulted from the submersible pump decon <br /> practices. The wells were sampled in the following order: MW9, MW7, MW6, MW4, MW5, and <br /> MW11. These wells in the past have all been below laboratory lower detection limits. The <br /> following wells which have shown petroleum hydrocarbons in past samplings were then sampled in <br /> the following order: MW12, MW8, MW1,.• MW2, MW 13, MW3, and MW 10. The pump (Grundfos Redi-Flog) was washed and rinsed after each well. The final rinse was sampled and contained the <br /> following concentrations TPHg 0.12 mg/L, Benzene 1.6 ug/L, Toluene 12 ug/L, Ethylbenzene 5.5 <br /> ug/L, Xylenes 39 ug/L and MTBE <5ug/L. <br /> 1 R603 Update#50 12197 <br />