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z <br /> San Joaquin County <br /> P.P. Environmental Health Department DIRECTOR <br /> Donna Heran, REHS <br /> z: ? 600 East Main Street <br /> a: A PROGRAM COORDINATORS <br /> N Stockton, California 95202-3029 <br /> Robert McClellon,REHS <br /> • Jeff Carruesco,REHS, RDI <br /> 0q .sjgov.org/ehd Kasey Foley,REHS <br /> Website: www <br /> F o R <br /> Phone: (209) 468-3420 Linda Turkatte,REHS <br /> Fax: (209)464-0138 <br /> May 16, 2011 <br /> Messrs. Kirk Larson, PG, and Robert Trommer, CHG <br /> State Water Resources Control Board <br /> Division of Financial Assistance <br /> 1001 1 Street <br /> Sacramento CA 95814 CUF Claim No. 5820 <br /> Subject: 139 Center Street S, Stockton CA <br /> Former Chevron Station # 9-0557 <br /> March 2011 Five-Year Review Letter Recommendations <br /> San Joaquin County Environmental Health Department (EHD) has received and reviewed the five- <br /> year review letter dated 15 March 2011 from Kirk Larson of the State Water Quality Control Board <br /> (SWQCB) Cleanup Fund (CUF) for the above-referenced site. The CUF recommended that the <br /> EHD consider the site for closure. <br /> The CUF has previously recommended that remediation be implemented to achieve water quality <br /> objectives (WQOs) in a timely manner and the EHD has issued such directives. In the recent <br /> 5-year review letter, the CUF has determined that the plume of impacted groundwater is <br /> adequately delineated, the most impacted groundwater is limited to the area near the former <br /> underground storage tank (UST) pit, and that contaminant concentrations will achieve WQOs in <br /> tens to hundreds of years. Based on these conclusions the recommendation for closure <br /> consideration was issued. <br /> The EHD has reviewed the site with the CUF recommendations in mind. The EHD concurs with the <br /> conclusions of the CUF; however the EHD requests that the CUF reconsider its closure <br /> recommendation. Recently a cone penetration testing (CPT) investigation of the site has been <br /> completed and a report on the results of the investigation is in preparation. Available data indicate <br /> that soil in the former UST area is intensely impacted to at least 62 feet below surface grade (bsg) <br /> with the depth to groundwater currently near 21 feet bsg, placing a large volume of impacted soil in <br /> direct contact with groundwater which may account for the very slow decline of contaminant <br /> concentrations in groundwater. A modest attempt at site remediation to remove the more volatile <br /> and mobile portion of the contaminant mass may greatly accelerate the time required to achieve <br /> WQOs. In the opinion of the EHD, it would be wise to evaluate the report of findings for the recent <br /> CPT investigation and implement at least a limited attempt at site remediation before issuing a <br /> closure recommendation. <br /> The EHD has prepared the following graph to analyze the contaminant concentration trends in key <br /> monitoring wells. <br /> 5-Year Review Letter Response 0511.doc <br />