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N CLEARWATER -� greater and 159,000 percent greater, respectively. On the basis of these results, it was concluded that concentrations of these COCs had increased and that a sorbed-phase source mostly likely remained in the soil and contributed to the increase in contaminant concentrations. With approval from the SJCPHS-EHD, the oxygen infusion system was re-started on December 15 and 16, 2010, and has been operated continuously to reduce off-site migration of COCs in groundwater. This Updated CAP addresses this new information that was first presented in the 2009 SCM and reinforced by the rebound test that a sorbed-phase source area is present and contributing to COC concentrations in the groundwater. Table 1 "Cumulative Soil Analytical Results" presents data on soil collected from the site. In the November 23, 2009, Third Quarter 2009 Rebound Evaluation and Groundwater Monitoring Report, Clearwater recommended that the CAP be updated for evaluation of effective source area remediation methods and technologies in the vicinity of wells AS-1 , IW-7, IW-6, and DPW-1 (hot-spot). Without remediation of this source area, COCs will move from the sorbed-phase to the dissolved phase and migrate into the groundwater. The source will need to be removed or degraded in place before groundwater remediation alone can be successful. In February 2002, prior to the installation of the oxygen infusion system, Clearwater performed a feasibility study in February 2002 at the site to measure the effectiveness of two different remediation technologies: 1) combined groundwater extraction and soil vapor extraction (GWE/SVE - now known as dual phase extraction, or DPE), and 2) air sparging combined with GWE/SVE. The DPE test was performed at well DPW-1 , and the air sparging was performed at well AS- 1 . DPE performed alone was shown to be impractical at this Site, mostly because of its small radius of influence, relatively low removal rates of benzene and TPH-g, and high relative cost. Data collected at the end of the test showed that the removal concentration of TPH-g was 77 m m andat of benzene was 0.70 mg/m3 (at a maximum tested vacuum of 50 inches of water). These low removal rates were attributed to the low permeability/transmissivity of the subsurface material. DPE performed alone was determined to be infeasible because a large number of wells would need to be installed across the site for the entire sorbed-phase area to be e, adequately remediated, having a horizontal radius of influence of only 6 to 8 feet. In contrast, DPE in combination with air sparging (AS) was shown to have an improved effective radius of influence. Air sparging, which is the application of air via positive pressure across the li subsurface material, was more effective than soil vapor extraction, which is the application of negative pressure across the subsurface material (vacuum), and an effective radius measured positive pressure at 60 feet from the air sparge well AS- 1 . An air sample collected using DPE combined with AS had a TPH-g concentration of 1 ,000 mg/m3 and a benzene concentration of 3.7 mg/m3, which exceeded those in the air sample collected during the DPE test without AS by 2 orders of magnitude. Whereas DPE alone had a horizontal radius of influence of approximately 6 to 8 feet, AS in combination with DPE with its 60-foot radius may be effective as a treatment method for sorbed-phase contaminants. Data from the 2002 feasibility study are provided in Table 2. Extrapolating from the success of applying positive air pressure on the l Floyd Barnes 2 Updated CAP ZB178 Update to CAP March 2010