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l , • ` Sequoia 680 Che peakc Drive Redwood City,CA 9400 (415) 364-9600 FAX(415) 364-9233 404 N.Wiget lane Walnut Creek,CA 94598 - (510) 988.9600 FAX(510)988-96404 N.Wiget lane Walnut Creek,CA 94598 - (510) 988.9600 FAX(510)988-9673 Analytical 819 Striker Avenue,Suite 8 Satnnnento,CA 95834 (916) 921-9600 FAX(916)921-0100 Mr. Tony Martin Kleinfelder 2825 East Myrtle Street Stockton, CA 95205 Subject: Method Blank Contamination from Acetone. This laboratory narrative is for the following projects that were analyzed for Semi- Volatile Organics by EPA Method 8270+ Open Scan: Sequoia I.D. Client Project I.D. Date Received/ COC# 1. 7010413-0442 20-397801.WR4 Spreckels 1/14/97 241, 242 2. 7010397-0400 20-397801.WR4 Spreckels 1/14/97 606 3. 6121287-1302 20-397801.WR6 Spreckels 12/31/96 296 4. 7010363-0375 20-397801.WR4 Spreckels 1/13/97 605 5. 6121077-1079 20-397801.WR4 12/23/96 193 6. 6121065-1073 20-397801.WR5 12/23/96 186 7. 7010455-0459 20-397801.WR6 Spreckels 12/27,31/96 295, 296 8. 7011286-1301 20-3978-01-W13 12/31/96 11949 Sequoia Analytical in Sacramento received samples from Kleinfelder during the time period of December 1996 through January 1997 for EPA 8270 + Open Scan. On these projects Sequoia Analytical reported several hits on the Open Scans for the above projects. Sequoia Analytical was requested to review the Open Scan results for the initial batches of samples submitted in December to verify if the reported compounds were actually in the samples. Because the reported compounds were not detected in the method blank for these batches, it was thought that the possibility of lab contamination was slight if at all. Towards the end of this project, it was noted that similar compounds were seen in the method blank as in the samples. Sequoia Analytical then pulled all of the EPA 8270 raw data for the entire project and it was discovered that through out the project there had been a trend of 1 to 4 compounds that continually showed up in the Open Scans at about the same concentrations in the samples and in the method blanks. After further investigation of the different solvents and different lots it was determined that a new lot of Acetone being used during the extraction process was contaminated with similar compounds, at similar concentrations, as reported on the following pages. It is Sequoia Analytical's policy as well as an industry standard to not subtract method blank concentrations from sample concentrations. However, it is believed that the compounds which were consistently detected in the method blanks and the samples were present due to the contaminated lot of Acetone used in the extraction process. A summary of the compounds are as follows.