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RECEPIEDD <br /> DEC is 1 2009 <br /> (\� Department of Toxic Suft"Nul of <br /> MaziarMovassaghiU'r j..FS <br /> Linda S.Adams Acting Director Arnold Schwarzene er <br /> Secretary for 8800 Cal Center Drive Governor BB <br /> Environmental Protection Sacramento, California 95826-3200 <br /> December 30, 2009 <br /> Mr. Maurice Benson <br /> Defense Logistics Agency <br /> Defense Distribution Depot San Joaquin, Sharpe Site <br /> Post Office Box 960001 <br /> Stockton, California 95296-0250 <br /> COMMENTS ON THE DRAFT HYDRAULIC FRACTURING AND INJECTION OF EHC <br /> PILOT STUDY RESULTS REPORT FOR DEFENSE DISTRIBUTION DEPOT SAN <br /> JOAQUIN CALIFORNIA (DDJC), SHARPE SITE, LATHROP, CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> evaluation report on October 23, 2009, submitted by URS Corporation on behalf of the <br /> Defense Environmental Support San Joaquin California. <br /> The EHC Pilot Study Report provides the detailed results of a pilot study conducted in <br /> saturated soils in the P-5A source area located in the Central Area of DDJC-Sharpe. <br /> The pilot study used hydraulic fracturing techniques to create preferential pathways to <br /> allow better distribution and increase the effectiveness of the carbon-coated zero valent <br /> iron amendment manufactured by Adventus (EHC). The EHC amendment is designed <br /> to enhance the anaerobic degradation and chemical reduction of tricholorethene (TCE) <br /> and its breakdown products in groundwater. <br /> Background <br /> Implementation of the EHC with hydraulic fracturing started on August 19, 2009 and <br /> was in response to noticeable increases in TCE contaminant concentrations found in <br /> monitoring well MW437C. In 2003, TCE concentrations in MW437C located in the <br /> Central Area increased from approximately 150 micrograms per liter (pg/L) to 650 pg/L, <br /> indicating that a persistent source remained up-gradient in the vadose zone. Follow-up <br /> fieldwork efforts detected and delineated the vadose zone contamination located at the <br /> end of a former runway, previously closed as a No-Further Action site, named P-5A. <br /> ® Printed on Recycled Paper <br />