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RECEMEDD <br /> U'U 3 T 2009 1G� <br /> ENVIRONMENT HEALTH <br /> PER�ijOW&Vant of Toxic Substances Control <br /> Maziar Movassaghi <br /> Linda S.Adams Acting Director Arnold Schwarzenegger <br /> Secretary for 8800 Cal Center Drive Governor <br /> Environmental Protection Sacramento, California 95826-3200 <br /> December 30, 2009 <br /> Mr. Maurice Benson <br /> Remedial Project Manager <br /> Defense Distribution Depot—Sharpe Site <br /> P.O. Box 960001 <br /> Stockton, California 95296-0320 <br /> COMMENTS ON THE DRAFT OFF-DEPOT POTABLE WELL CONTINGENCY PLAN <br /> FOR DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN CALIFORNIA (DDJC), <br /> SHARPE SITE, LATHROP, CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> report on October 6, 2009 submitted by the URS Corporation on behalf of Defense <br /> Enterprises Support San Joaquin California (DESJC). <br /> The report provides the framework for establishing response actions if contaminants of <br /> concern (COCs) originating from DDJC-Sharpe are impacting or could potentially <br /> impact down-gradient potable water supply wells (PWs) used by human receptors. <br /> Specifically, the Contingency Plan identifies a group of 34 wells that fit into two <br /> categories: affected wells; and, wells potentially in the flow path of contaminant plumes <br /> originating from DDJC-Sharpe. The Plan establishes warning levels, equivalent to the <br /> Record of Decision's Aquifer Cleanup Level (ACL) for the COCs detected in these <br /> potable wells. If the COC warning level is exceeded in any of the PWs sampled, then a <br /> more aggressive sampling approach is adopted, including 30-day repeat sampling, <br /> quarterly sampling for one-year, a new response action adopted which may include <br /> continued quarterly sampling or adding wellhead treatment. <br /> General Comments <br /> 1.) The potable well contingency plan proposes significant reductions in sampling <br /> frequencies for off-site potable wells. In some cases sampling frequencies have <br /> been reduced from quarterly to every five years, and in other cases eliminated <br /> completely from the DDJC-Sharpe groundwater monitoring program. The basis <br /> for the significant reductions in sampling for off-site potable wells is to reduce the <br /> ® Printed on Recycled Paper <br />