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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 Breakthrough pressure was observed at 24 psig. This pressure is greater than the estimated breakthrough pressure, and below the overburden pressure of the formation. The overburden pressure (Gma x) represents the upper limit for injected air pressure and is calculated as follows assuming a dry soil density of 100 pounds per cubic foot: Gmax (psi) = 0.7 (psi/foot) x Total Depth (feet)(base of screen) 4.5.2 Injection Flow (AS-2 Testing) Once breakthrough testing was completed, SGI conducted "low-flow, "medium-flow", and "high- flow" steps to evaluate the feasibility of AS within a range of flows. During low-flow testing, the injection flow rate was maintained at an average of approximately 2 scfm at an average of 11 psig after psig readings equilibrated following breakthrough. During medium-flow testing, the injection flow rate was maintained at an average of approximately 7.5 scfm at and average of 14 psig. During high-flow testing, the injection flow rate was maintained at an average of approximately 15 scfm at an average of 15 psig. Air injection was conducted for a total of approximately 6 hours (2 hours for low-flow, 2 hours for medium-flow and 2 hours for high flow). Throughout each step, relatively stable pressure and flow readings were observed (i.e. once flow was set, pressure did not need to be reduced to prevent flow from increasing significantly). Additionally, only a minor pressure increase was required to increase the flow rate from the low- to the medium-flow rate and from the medium to high-flow rate. 4.5.3 Pressure Response (AS-2 Testing) Pressure in the observation wells was measured periodically using the magnehelic gauges during, and after the air injection phase of testing for AS-2. Any stored pressure remaining in wells OBS-1 and VW-1 was released between the two sparge tests ensuring that the background pressure was zero. Induced pressures observed in observation wells during AS is summarized below: During the low-flow injection step (2 scfm), induced pressure in OBS-1 was observed at a range of 0.25 "H2 0 to 1.6 "H20, induced pressure was not observed in VW-1 and AS-1; During the medium-flow step (7.5 scfm), induced pressure in OBS-1 was observed at a range of 1.4 "H20 to 1.9 "H2 0, induced pressure in VW-1 was observed at a range of 0 "H20 to 0.15 "H2O, and no induced pressure was observed in AS-1; and During the high-flow step (15 scfm), induced pressure in OBS-1 was observed at 5 "H2O, induced pressure in VW-1 was observed at a range of 0.2 "H20 to 0.25 "H2O, and no induced pressure was observed in AS-1. Pressure returned to measured background levels (0 "H20) within approximately 40 minutes following the completion of the air injection phase of testing, indicating rapid pressure dissipation in the subsurface (Graph 2A). 4-8 The Source Group, Inc.