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0 <br /> Former Countryside Market,Stockton,California <br /> Feasibility Study and Interim Remedial Action Plan May 20,2013 <br /> 7.0 INTERIM REMEDIAL ACTION PLAN <br /> Sparging is proposed at the Site to cleanup the dissolved hydrocarbon plume and enhance vadose <br /> zone soil remediation via natural attenuation processes. The potential benefits of this technology <br /> include: 1) plume stabilization; 2) increased available subsurface oxy to promote biodegradation <br /> (for both soil and groundwater); and 3) hydrocarbon constituent volatilization/removal from the soil <br /> and groundwater into the vapor phase for passive treatment. <br /> In addition to the proposed feasibility testing activities (Section 5.0), the p imary lines of evidence that <br /> will be used to demonstrate the effectiveness of sparging will include 1) observed reductions in <br /> contaminant concentrations along the groundwater flow path during rou ine groundwater monitoring <br /> and sampling activities, 2) down well field data documenting enhanced rakes of biodegradation via the <br /> periodic deployment of dataloggers in key wells, and 3) analytical bioremediation and geochemical <br /> indicator monitoring data that will serve to confirm the plume constituents are being fully degraded to <br /> nontoxic end products downgradient. <br /> 7.1 Implementation Strategy <br /> While sparging is the presumptive remedial technology that will be utilized at the Site (to be confirmed <br /> via feasibility testing), it is important to underscore that an adaptive approach will be employed to <br /> formulate a final RAP. Thus, soil and bioremediation/geochemical indicator data to be collected <br /> during feasibility testing activities along with the testing results, as wall as ongoing groundwater <br /> monitoring and sampling data will all be utilized as part of the TRAP. Foi example, should the former <br /> UST area soil data warrant closer consideration, proposed well VW-1 will be utilized for this purpose, <br /> including potential future remedial use via bioventing or another viable technology. Similarly, if the <br /> data indicates a more refined understanding of the downgradient area is required to effectively target <br /> and implement a final remedial approach for this portion of the plume the utilization of advanced <br /> subsurface characterization technologies may be employed, if feasible. <br /> Additionally, given that the lead scavenger 1,2-DCA is the only plum constituent that has been <br /> detected above its MCL in the furthest downgradient monitoring well MW-7) and a domestic well <br /> (10967 Copperopolis Road located approximately 300 feet downgradie�nt of the former UST area), <br /> and knowing the general persistence of this compound in the enviro ment, the final RAP will be <br /> developed to specifically target this constituent rather than simply having general applicability to <br /> petroleum hydrocarbons. As a result, while the purpose of this TRAP it to evaluate the effectiveness of <br /> cleanup following implementation of the proposed treatment technology, achieving 1,2-DCA <br /> concentration reductions must be a primary focus and objective of a long term remediation strategy. <br /> The proposed TRAP strategy is to initially implement source control measures via sparging (assuming <br /> this technology is determined to be feasible) and monitor/evaluates downgradient groundwater <br /> conditions for signs of improvement as cleanup of this primary region �f the plume is anticipated to <br /> Feabillty St y aM lFeasiEllily 5"&lF PTert Flnal.dx 7-1 The Source Group,111L <br />