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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 approximately six hours (two hours for low-flow, two hours for medium-flow, and two 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 create a significant increase in flow. 4.4.3 Pressure Response (AS-1 Testing) Pressure in the observation wells was measured periodically using the magnehelic gauges before, during, and after the air injection phase of the testing. Background pressure monitoring (using magnehelic gauges) before air injection confirmed that there was no background pressure in the observation wells. Induced pressures observed in observation wells during AS is summarized below: During the low-flow injection step (5 scfm), induced pressure in OBS-1 was observed at a range of 0.55 inches of water ("H20) to 1.2 "H2 0, induced pressure in VW-1 was observed at a range of 0 "H20 to 0.15 "H20, and no induced pressure was observed in AS-2; During the medium-flow step (10 scfm), induced pressure in OBS-1 was observed at a range of 0.6 "H2 0 to 2.3 "H2 0, induced pressure in VW-1 was observed at a range of 0 "H20 to 0.15 "H20, and no induced pressure was observed in AS-2; and During the high-flow step (20 scfm), induced pressure in OBS-1 was observed at 5 "H20 to 2.3 "H20, induced pressure in VW-1 was observed at 0.25 "H2 0, and no induced pressure was observed in AS-2. Pressure returned to measured background levels (0 "H20) within approximately 10 to 20 minutes following the completion of the air injection phase of testing (Graph 1A), indicating rapid pressure dissipation in the subsurface (i.e., injected air is not being "trapped" in the formation). The field monitoring data (tabulated) collected during the test is provided as Appendix I, observation well head pressure readings collected by the data loggers are in Graph 1A, and Troll data is included in Appendix J. 4.4.4 Groundwater Level Changes (AS-1 Testing) Groundwater mounding is a potential indication of AS influence since the rise in groundwater levels is attributable to the addition of air into the saturated zone at or near that location. To monitor for the effect of air injection into AS-1, groundwater levels were monitored and recorded before, during, and after the injection phase of testing using the data loggers. Graph 1B shows changes in water levels versus time (raw data logger data in Appendix J). Apparent displacement was observed in observation wells OBS-1, AS-2, and MW-5 during each step of testing. The groundwater levels in each observation well showed slight increases in response to initiation of AS testing and changes in AS flow rate. After an initial increase in 4-5 The Source Group, Inc.