ARCHIVED REPORTS_XR0005381 - Laserfiche WebLink

Home Browse Search

1.4 Laboratory Analysis The three water samples were relinquished to Sequoia Analytical Laboratories of Sacramento, California for analysis of the following constituents: • TPH-Extractable as Diesel (TPH-D) by Method 8015M + Benzene, Toluene, Ethylbenzene, Xylenes (BTEX) and Methyl tert-butyl ether (MTBE) by Methods 8015MJ8020 • Oxygenates (Method 8260) The samples were analyzed on a 5-7 day rush turnaround schedule. 2 FINDINGS No odor, product layer or sheen were observed in the samples from each of the three wells sampled. Analytical results did not detect concentrations of BTEX or Oxygenates above p Y laboratory reporting limits in the three water samples submitted for analysis. MTBE was reported in MW-3 at a concentration of 15.9 µg/l in the 8020 analysis and was not detected in the EPA Method 8260 analysis. Previous sampling conducted by Kleinfelder in June 1998 did not report MTBE above Iaboratory reporting limits in each of the three wells sampled. The US EPA has established a drinking water advisory limit of 20-40 µg11 and the State of California has established a drinking water advisory limit of 35 µg11 for MTBE. Discussion with the analytical laboratory regarding the apparent presence of MTBE in the Method 8020 analysis indicates that this method (EPA Method 8020) was not originally intended to be used to analyze for MTBE. The reason is that since MTBE is a lighter fraction hydrocarbon, it has a tendency to co-elute. However, the regulatory community has indicated that to confirm the presence of MTBE by EPA Method 8020, the sample should also be analyzed by EPA Method 8260 (GC/MS). EPA Method 8260 is more accurate in detecting the presence of MTBE than the EPA Method 8020 analysis. The EPA Method 8260 analysis did not report concentrations of MTBE above the method reporting limit of 2.0 µg11 and as such, it is the laboratories opinion that the reported MTBE is a false-positive. TPH-D was reported in the sample from MW-1 at a concentration of 0.0629 mg/L. This concentration was slightly above the reporting limit of 0.050 mg/L. The remaining two samples contained no detectable extractable hydrocarbons. Copies of the laboratory data sheets along with the laboratory reporting limits are presented in Appendix B. 3 DISCUSSION TAH-Extractable as Diesel was reported at a concentration just slightly higher than the reporting limit of 0.050 mg/L in monitoring well MW-1. Previous sampling conducted in June 1998 also 40-327301/40188051 4 Copyright 1998 Kleinfelder. Inc. KLEINEELDER 780 Chadbourne Road, Suiie D, Fairfield CA 94585-9('43 (707)429-4070 (707)429-4162 fax