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TreadweIIW) <br /> A LANSAN COMPANY <br /> Request for Low-Threat Case Closure 6 June 1013 <br /> RWQCB case#391149 and#391162 Page 15 <br /> 420 and 413 N Madison Street <br /> Stockton,California <br /> Project:731589001 <br /> The Sites meet the LTCP criteria for vapor intrusion to indoor air. Benzene was not detected in <br /> groundwater or soil associated with UST B,6 at 423 Madison, and was.only detected in <br /> groundwater at Carando.,The benzene detections at Carando aren't beneath or near existing <br /> buildings and are one to two orders of magnitude below the groundwater ESL for potential vapor <br /> intrusion for commercial land use. <br /> • The Sites meet the criteria for direct contact and outdoor exposure based on the LTCP. <br /> • 423 N Madison meets the LTCP groundwater-specific criteria. <br /> • The extent of the benzene plume at Carando has been estimated by using BioScreen, an industry <br /> standard approach for modeling sites with dissolved hydrocarbon releases to groundwater. <br /> BioScreen uses site specific input parameters and first order decay constant, and therefore is a <br /> reasonable estimate of the benzene plume extent. <br /> • The remaining masses of TPH in soil and groundwater at both sites were estimated using most _ <br /> recent available data from 2005 and earlier, and the current remaining TPH mass at each site is <br /> likely less than the mass estimated due to biodegradation. <br /> • Both sites are located more than 2,000 feet from the nearest water supply wells and are down- <br /> gradient from the nearest surface water body. <br /> Given the above case closure justifications, we respectfully request that case closure be granted. <br /> If you have any questionsafter reviewing this report, please call Jeremy Gekov at(510) 874-7027. <br /> Sincerely yours, <br /> Treadwell&Rollo, A Langan Company <br /> \pNAL GFr7 <br /> rocs �p� <br /> a JEREMY GEKOV' �'� <br /> No.8800 <br /> Jeremy Gekov, PG Dorinda Shipman, PG, CHG <br /> Project Geologist OFCPrincipal/Vice President <br /> cc: Patrick Willis, Stockton Arena Hotel &Conference Center, LLC <br /> Joel Levy, Hefner Stark& Marois, LLP <br /> Nuel Henderson, San Joaquin County.-Environmental Health Department <br /> 731589001.02 JG <br />