SITE INFORMATION AND CORRESPONDENCE

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i t Morita Brothers 1..i 814 E. Charter Way page 3 of 3 Stockton, California 06 February 2009 still be increasing in MW-109, and were 24.6 pg/L as of November 2008. The EHD has discussed these observations with Jim Barton of the Central Valley Regional Water Quality Control Board (CVRWQCB). Both the EHD and the CVRWQCB believe at least two more quarters of data from MW-109 is needed to verify the model the EHD has of the site.; if the EHD concept is correct, the MTBE concentrations will not increase sharply, but should stabilize at approximately 25 tag/L or should start declining. To collect the data needed to verify the model of a migrating low mass plume posing minimal risk to sensitive receptors, human health and additional groundwater supplies, the EHD cannot concur with the closure request at this time. "This decision is subject to appeal to the State Water Resources Control Board (State Water Board), pursuant to H&SC Section 25296.40(a)(1), (Thompson-Richter Underground Storage Tank Reform Act — Senate Bill 562). Please contact the State Water Board Underground Storage Tank Program at (916) 341-5752 or visit the State Water Board internet website at http://www.waterboards.ca-gov/ust/cleanup/petitions.html for information regarding the appeals process." To minimize the work required on your site, the EHD has determined that the groundwater sampling program can be reduced to the following: • Quarterly— MW-106, MW-108, MW-109 and MW-208; • Annually — MW-2, MW-7, MW-107 and MW-209 (next sampling in November 2010, if needed); and • Biennially — MW-1, MW-3, MW-4, MW-5, MW-6, MW-11, MW-104, MW-110, MW-111, MW-202 and MW-210 (next sampling November 2011, if needed). Analyze MW-108 and MW-208 only for TPH-g and MW-106 and MW-109 only for MTBE; analytical needs of the other wells will be determined before the next sampling date for those wells. The EHD has presented GTI this sampling schedule for immediate implementation, which is expected this week; GTI will move up the sampling date for the second quarter 2009 by one month to April to see if the data trend will be favorable for closure consideration. Questions or comments may be directed to Nuel Henderson at (209) 468-3436. Sincerely, Nuel C. Henderson, Jr., PG Margaret Lagorio, REHS Engineering Geologist Program Coordinator C: James . Barton, PG —CVRWQCB, 11020 Sun Center Dr. #200, Rancho Cordova, CA 95670 R. Kablanow, PG—Geological Technics Inc., 1101 Seventh St., Modesto, CA Closure Request Response and Monitoring Frequency Letter 0209