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Treadwell&Rollo <br /> A LANGAN COMPANY <br /> Request for Low-Threat Case Closure 6 June 1013 <br /> RWQCB case#391149 and#391161 Page 13 <br /> 420 and 423 N Madison Street <br /> Stockton,California <br /> Project:731589001 <br /> Guideline Justification for Site Closure(423 N Madison) <br /> located within 2,000 feet of the Site. <br /> The unauthorized release consists only of Only releases related to petroleum products have <br /> petroleum (including oxygenates). been detected at the Site. <br /> The unauthorized release has been stopped. All known USTs have been removed from the Site. <br /> Free product has been removed to the maximum Free product has never been detected at the Site. <br /> extent possible. <br /> A conceptual site model has been developed. A conceptual model has been prepared and is <br /> supported by previous documents as well as figures <br /> and tables provided with this closure request. <br /> Secondary source has been removed to the extent Secondary sources include residual impacts in soil <br /> practicable. and shallow groundwater. The over-excavation <br /> around UST B-6 in 2004 removed the majority of <br /> the secondary source in soil. Petroleum <br /> hydrocarbons or BTEX have not been detected in <br /> shallow groundwater samples collected from <br /> borings or monitoring wells down-gradient of UST <br /> B-6 indicating limited impact by the release from <br /> UST B-6, or that concentrations attenuated prior to <br /> reaching down-gradient sampling locations. <br /> Soil and groundwater have been tested for MTBE, Soil and groundwater have been tested for MTBE, <br /> and results have been reported in accordance with which has not been detected (Attachment 2). <br /> Health and Safety Code section 25296.15 (indicates <br /> that results of MTBE tests are known to the <br /> Regional Water Board). <br /> Nuisance as defined by Water Code section 13050 Groundwater impacts are not considered to be a <br /> does not exist at the site (indicates no nuisance nuisance due to the lack of contact with human or <br /> odors or threat to public health and safety). other ecological receptors. Depth to groundwater <br /> has been between approximately 16 to 18 feet bgs <br /> historically, which is deeper than potential future <br /> trenching work. Also, shallow groundwater at the <br /> Site has consistently flowed to the north-northeast <br /> away from McCleod Lake, located upgradient <br /> approximately 400 feet to the southeast. <br />