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`- California Regional Water Quality CoRrol Board ( F <br /> Central Valley Region <br /> Linda S.Adams Arnold <br /> Secretary for Katherine Hart, Chair Schwarzenegger <br /> Environmental 11020 Sun Center Drive#200, Rancho Cordova,California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://w .waterboards.ca.gov/centralvalley <br /> REGMEWDD <br /> 3 May 2010 MAY 0 0 L0 i0 <br /> ENVIRONiVILK HEALTH <br /> DESJC, M.BENSON PER MIMSERViCES <br /> Defense Distribution Depot San Joaquin <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> UST 25 TECHNICAL MEMORANDUM, DEFENSE DISTRIBUTION DEPOT <br /> SAN JOAQUIN— TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff has reviewed the April 2010 UST 25 Technical Memorandum, received <br /> 15 April 2010, and Revision to Draft UST 25 Technical Memorandum, received 20 April <br /> 2010. Engineering-environmental Management Inc., prepared the memorandum on behalf of <br /> Defense Logistics Agency Enterprise Support San Joaquin, California (DLA) for the Defense <br /> Distribution Depot Tracy Site (DDJC Site), located in Tracy, California. The Technical <br /> Memorandum summarizes the results of cone penetrometer test (CPT) borings advanced in <br /> January 2009 and February 2010 adjacent to Building 255 at the DDJC Site. <br /> The objectives of the CPT investigations were to delineate the extent of petroleum <br /> hydrocarbons, naphthalene, and 2-methylnapthalene in groundwater. The data are <br /> presented to support the proposed placement of groundwater monitoring well screens, and <br /> presumably will be utilized in modeling the potential for migration of organic compound <br /> vapors into Building 255. <br /> Comments <br /> Central Valley Water Board staff comments are presented below. <br /> 1. Staff concurs with the number and placement of the groundwater monitoring wells <br /> proposed on Figure 9 of the Technical Memorandum revision received on 20 April 2010. <br /> 2. DLA has not yet presented modeling results that estimate potential risk to human health <br /> from air inside of Building 255. DLA should consider concentrations of diesel fuel <br /> constituents in both soil and groundwater samples. For the purpose of modeling, DLA <br /> should assume that liquid-phase petroleum hydrocarbons are floating on the water table <br /> beneath Building 255. DLA should conduct the modeling and present the results with <br /> recommendations as soon as possible. <br /> California Environmental Protection Agency <br /> CIS Recycled Paper <br />