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CAMBRIA concentration of 2,800 ppb, however, analysis by EPA Method 8260A did not confirm this MTBE concentration Quarterly Sampling Groundwater samples were analyzed for total purgeable hydrocarbons as gasoline (TPHg) according to EPA Method 8015 (Modified) and benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tertiary butyl ether (MTBE) according to EPA Method 8020 Groundwater samples collected from well MW-7 were also analyzed for MTBE according to EPA Method 8260A Field monitoring data and chemical analytical data are presented in a summary table to Blaine's groundwater monitoring report (Appendix A) MTBE Detection Limit In our January 31, 2000 Response Letter/Work Plan, we indicated we would be able to meet • your request for lower MTBE detection limits We discussed the lower detection limits with Sequoia Analytical Labs (Sequoia) and they indicated they could meet the 0 5 to 1 0 ppb detection limits with EPA Method 8020 We were told later by Sequoia that this was a mistake, they could not get these low detection limits by EPA Method 8020 Therefore we will not be able to achieve these lower detection limits as we previously indicated unless we use the more expensive EPA Method 8260 At this point we do not recommend performing the EPA Method 8260 analysis on all of the monitoring wells at this site Conclusions Groundwater samples collected from the wells this quarter contained concentrations of petroleum hydrocarbons and MTBE consistent with historical ranges for this site Closing Cambria submitted a work plan to SJCPHS on January 31, 1999 for further investigation at this site SJCPHS approved this work plan and we are pursuing access agreements and encroachment permits for the proposed off site monitoring wells The two proposed onsite soil borings are tentatively scheduled to be drilled May 23 and 24, 2000 • Quarterly monitoring and sampling will continue on the established schedule for this site 0854 2