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JAN 04 '99 03 ZBPM SEQUOIA/SAC P 2 <br /> Sequoia 680 chesaprake Drive Redwood City,CA 94063 (650)364-9600 FAX(650) 364-9233 <br /> 4D 404 H Wlgat Lane walnut Creek.CA 9x598 (925)988-96Co FAX(935)988-x673 <br /> Analytical 8195rrIker Avenue,Wre B Sacramento,CA 95834' (916)ox1-9400 FAX(916)921-0100 <br /> 1455 McDowell Blvd North Ste D Petaluma.CA 94954 (707)792-1865 FAX(707)792.0342 <br /> Ms Chris Brown <br /> Pacific Environmental Group <br /> 11315 Sunrise Gold Circle Ste M <br /> Rancho Cordova, CA 95742 <br /> Subject- Methanol Reporting Limit and MTBE Quality Control Data <br /> PEG Protect ID, Unocal 0123, Tracy, CA <br /> Sequoia Analytical Project ID, 5810088, S810250 <br /> Dear Ms Brown- <br /> During our recent telephone conversation two issues wore raised concerning site <br /> Unoca10123 The first issue concerned the reporting limit for methanol analysis and the second <br /> issue concerned the quality control data for MTBE analysis This Ietter is intended to clarify the <br /> data reported to resolve any concerns you may have <br /> The methanol(Sequoia Analytical Project ID 5810088)was analyzed using a modified SW-846 <br /> 8015 method as no formal method for analyzing methanol has been specified by any regulatory <br /> agency No detection limit for methanol is specified in SW-846 8015 The reporting limit of 10 <br /> mg/1 is at the method detection limit and cannot be lowered Due to the physical properties of <br /> methanol, SW-846 8260 is not a viable option for analysis <br /> The MTBE(Sequoia Analytical Project ID S8 10250)was analyzed using a modified SW-846 <br /> 8020 method All sample batches are validated using quality control data from the method blank <br /> and the laboratory control sample Quality control data from the matrix spike/matrix spike <br /> duplicate are not used to accept or refect sample batches, as we have no control over the contents <br /> of the sample used Iii-house derived recovery and RPD limits are provided for advisory use <br /> only. The MTBE batch quality control sample associated with S810250 was from a client other <br /> than PEG A review of the quality control data confirmed that a coeluting organic compound <br /> interfered with the calculation of the MTBE results. This in no way indicates a problem with the <br /> Unocal 0123 samples submitted by PEG The footnote in the original report submitted was in <br /> error An amended footnote explaining the quantitation problem was inserted and an amended <br /> report has been generated <br /> I hope this letter removes any concerns you have regarding this project If you have any further <br /> questions, please call me at(916)921-9600 <br /> Sincerely, <br /> SEQUOIA ANALYTICAL <br /> Mark Chiaravalloti <br /> Interim Laboratory Director <br />