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uL HEAL IfI <br /> ..... UNITED STATES ENVIRONMENTAL PROTECTION AGENCY <br /> Region 9 r <br /> 75 Hawthorne Street 03 JUL 30 PH 4: 44 <br /> San Francisco CA 94105-3901 <br /> July 23, 2003 <br /> Mr. Marshall Cloud <br /> Defense Distribution Depot San Joaquin California, Tracy Site <br /> DDJC-FA,Attn: Environmental Management <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> RE: Memorandum, Recommendation to Shut Down Extraction Wells EW014A, <br /> EW016A, and EW017A, Defense Distribution Depot San Joaquin (DDJC) Tracy <br /> Site, Tracy, California,June 2003 <br /> Dear Marshall, <br /> Thank you for the opportunity to review the "Memorandum, Recommendation to Shut Down <br /> Extraction Wells EW014A, EW016A, and EW017A, Defense Distribution Depot San Joaquin <br /> (DDJC) Tracy Site, Tracy, California," dated June 2003. Our comments are attached. <br /> Three extraction wells are recommended for shut down: EW014A, EW 16A, and EW017A. <br /> Note that EW015A was also recommended for shut down in the 2002 DDJC-Tracy Annual <br /> Monitoring Report, but upon further evaluation, it was determined to have a slight increasing <br /> visual trend for TCE and is therefore no longer recommended for shut down. However, based on <br /> the time-series plot for EW014A included in the Memorandum, EW014A appears to show a <br /> similar increasing trend. The rationale used to determine why EW014A should be shut down is <br /> unclear. <br /> In addition, the recommendations state that the shut-down wells will be sampled quarterly <br /> for one year. If concentrations exceed the aquifer cleanup level (ACL), the extraction well will <br /> not be restarted until the ACL is exceeded for three successive quarters. This does not appear to <br /> be an appropriate strategy to maintain plume capture and minimize plume expansion. It is <br /> recommended that the Regional Program Managers (RPMs) discuss the protocol for shutting <br />