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CalifornifRegional Water Quality (ntrol Board <br /> Central Valley Region f!I WM ' <br /> Katherine Hart, Chair <br /> 11020 Sun Center Drive,#200,Rancho Cordova,California 95670-6114 <br /> Linda S.Adams (916)464-3291 • FAX(916)464-4645 Edmund G.Brown Jr. <br /> Acting Secretary for http://www.waterboards.ca.gov/centralvalley <br /> Environmental Protection Governor <br /> RECEIVED <br /> 8 February 2011 FEB 10 2011 <br /> ENVIRONMENTAL HEALTH <br /> P <br /> DESJC, M.BENSON ERMIT/SERVICES <br /> Defense Distribution Depot San Joaquin <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> OFF-DEPOT PRIVATE WATER SUPPLY WELL CONTINGENCY PLAN <br /> DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN— TRACY SITE <br /> The California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff has reviewed the February 2010 Final Off-Depot Private Water Supply <br /> Well Contingency Plan (Final Plan). URS Group, Inc., prepared the Final Plan on behalf of <br /> the Defense Logistics Agency Enterprise Support San Joaquin, California (DLA). <br /> The goal of the Final Plan is to protect the users of offsite private water supply wells located <br /> down-gradient of the DLA Tracy supply depot that may be in the flow path of groundwater <br /> plumes containing constituents of concern (COCs) that have migrated from the depot. The <br /> Final Plan establishes Notification Levels, Trigger Levels, and Action Levels for the <br /> following CDCs: trichloroethene (TCE) tetrachloroethene (PCE), cis-1,2-dichloroethene <br /> (cis-1,2-DCE), trans-1,2-DCE, vinyl chloride, and dieldrin. Also, the Final Plan identifies <br /> responses that DLA will implement if these levels were exceeded in any of the private wells. <br /> In addition, the Final Plan identifies the following five private water supply wells to be <br /> monitored for CDCs: PW001, PW004, PW006, PW007, and PW013. <br /> Central Valley Water Board staff has prepared the comments in this letter to assist DLA <br /> with development of an acceptable revised Final Plan. However, we will only approve <br /> groundwater sampling frequency changes that are presented in Annual Monitoring Reports <br /> required by the Record of Decision (ROD) documents for the Tracy site. As you know, <br /> DLA's next opportunity for change request approvals is our review of the Draft Final Well <br /> Monitoring Program 2010 Annual Monitoring Report, 4QO9— 3Q10. DLA has scheduled <br /> completion of the report after 18 February 2011. <br /> Central Valley Water Board Staff Comments <br /> DLA's Final Plan indicates that response actions, including water supply replacement will <br /> not be implemented if cis-1,2-DCE, trans-1,2-DCE, or vinyl chloride levels are exceeded in <br /> a private well unless TCE or PCE are also detected in the well. This is not acceptable to <br /> the Central Valley Water Board; if these breakdown products of TCE or PCE are detected, <br /> response actions must be implemented to protect public health. <br /> California Environmental Protection Agency <br /> ��_1 Recycled Paper <br />