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• • Page 2 of 3 (or every two years) monitoring events (with appropriate analytical data reporting limits) indicated ND levels. MW-5: BTEX (similar to MW-4) has been routinely reported in this well, in diminishing concentrations. It appears that MTBE data reported in 2006 through 2008 may have been impacted by high levels of other constituents, and this is reflected in very high laboratory reporting limits. Again, perhaps MTBE could be discontinued if several annual (or every two years) monitoring events (with appropriate R.L.) indicate ND levels. MW-6: BTEX has been sporadically reported in this well, in consistently low concentrations. TPH-g and MTBE have been reported to be present, also in low concentrations. With the predominant groundwater direction for the site to be estimated in the northeast direction, MW-6 is located down gradient of the former USTs and warrant sampling annually or once every two years. MW-8: BTEX, TPH-g and MTBE have been reported in this well, although a much lower levels than have been reported for MW-4 and MW-5. With the predominant groundwater direction for this site to be estimated in the northeast direction, it appears that MW-8 is located laterally with respect to the contamination plume. With the low levels reported for this well, it may be justified to sample this well at the same frequency as the historically ND wells. MW-9: This well is located in the center of the estimated contamination plume, and has routinely reported high levels of BTEX, TPH-g and MTBE. Similar to MW-4 and MW-5, it appears that the MTBE levels have been reported at a very high RL, impacted by the high levels of other contaminants during the laboratory analysis. This well should continue to be monitored on an annual basis or once every two years, and MTBE should be reported with an appropriate RL. Please let me know if you have any questions, or want to discuss further. 1 look forward to hearing from you soon. Thank you, Tamorah Bryant, P.E. Geological Technics Inc. 1172 Kansas Avenue Modesto, CA 95351 Tel 209 522 4119 Fax 209 552 4227 This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. If you are not the intended recipient you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited. I From: Mike Infurna [EH] [mailto:MInfurna@sjcehd.com] Sent: Thursday, April 23, 2009 11:25 AM To: Tamorah Bryant Subject: RE: IM Equipment- Revision to Additional Site Characterization Work Plan