ARCHIVED REPORTS_XR0007718 - Laserfiche WebLink

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Starting in the third quarter of 1997, as required by the Central Valley Regional Water Quality Control Board (CVRWQCB), samples were analyzed for Oxygenates by EPA Method 8260 The seven oxygenates which were sampled for are Da-isopropyl ether, Ethanol, Ethyl tert-Butyl Ether, Methanol, Methyl tert-Butyl Ether(MTBE), Tert-Amyl Methyl Ether, and Tert-Butanol MTBE is analyzed by EPA method 8260 MTBE concentrations are contoured in Figure 4 A summary of select analytical sampling results are provided in Table 1, and a copy of the laboratory analytical report is contained in Appendix B CONCLUSIONS The laboratory reports(Appendix B)indicated the presence of Methanol concentrations ranging from 7400 ug/L to 110,000 ug/L in monitoring wells TB-7, and MW-4, respectively This analyte was not expected in view of the sites's history and surrounding land use Thrifty reviewed these results with an independent organic chemist to determine a likely source of the Methanol in such large amounts Methanol is used as surrogate spike during QA/QC procedures and will show up an geochemical analyses of the Iaboratory equipment is not cleaned properly We believe the high concentrations of Methanol and TPH-g are suspect, because of possible laboratory contamination Figure 4 is based upon the reported TPH-g data and is suspect During the 2nd Quarter 1999, reported thus TPH-g concentrations in the site monitoring wells were in the range of non-detectable (<50 ug/L)to 15,000 ug/L (MW-5) Benzene concentrations an the site monitoring wells were in the range of non-detectable (<0 3 ug/L) to 1 7 ug/L (MW-5), and MTBE concentrations in the site monitoring wells were in the range of non-detectable (<20 ug/L) to 7,200 ug/L (TB-7) Thrifty has completed the process of installing a Thermo Baker unit The system will be operational on July 1, 1999 Mr Make Infurna, a representative of the San Joaquin County Health Department, is scheduled to be on site to witness the system start-up, along with Mr Jeff Suryakusuma, Director of Earth Management Comapny Mr Suryakusuma will answer any questions for Mr Infurna, and ensure the system as operational The required reports for system operation and monitoring will be sent to the appropriate oversight agencies Thrifty will continue the current groundwater monitoring and sampling program Any monitoring wells which are connected system will have to be resurveyed due to well modification All interpretations expressed in this report are based upon review of data collected by EMC Written by Reviewed by U w 4Rmond C Fraedrachsen R ssell Powers, 454` ' Project Manager P sect Manager , I , Environmental Geologist Geologist 11?P��