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EXECUTIVE SUMMARY <br /> GWE and SVE have been implemented at this site with marginal success. CRA <br /> completed the design of an AS/SVE system and solicited bids from installation <br /> contractors and equipment vendors. However, prior to system installation, CRA <br /> evaluated whether the potential risk to receptors warrants pursuing active remediation <br /> as planned and in consideration of the SWRCB's Draft Low-Threat UST Case Closure <br /> Policy. CRA evaluated four remediation technologies for the site: <br /> • DPE; <br /> • AS/SVE; <br /> • Excavation,and <br /> • MNA. <br /> In addition, CRA reviewed current site conditions. Groundwater monitoring data <br /> indicate that CDCs are defined in the down-gradient direction and that COC <br /> concentrations are decreasing in source area wells and stable to decreasing in <br /> cross-gradient wells. The subject site is an operating terminal on Rough and Ready <br /> Island near properties with historical heavy industrial use. These data suggest that there <br /> is limited risk to potential receptors. <br /> Our evaluation shows that the chemical plumes are adequately stable and retracting, <br /> and no sensitive receptors are at risk. Our evaluation further determined that MNA is <br /> the preferred remedial option and is adequately protective of health and the <br /> environment. Therefore, CRA recommends implementing MNA. CRA also <br /> recommends collecting bioparameters for one hydrologic cycle to assess the subsurface <br /> biological conditions. <br /> At a minimum, tabling the requirement for active remediation until a ruling on the draft <br /> UST low-threat closure policy occurs is requested. We also extend ourselves for a <br /> face-to-face meeting to further discuss details of site conditions and active remediation <br /> versus the risk-based approach. <br /> 247729(33) 1 CiONESTOGA-ROVERS&ASSOCIATES <br />