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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 5.0 AIR SPARGING TESTING SUMMARY AND CONCLUSION 5.1 Breakthrough Testing Air sparge breakthrough pressure in AS-1 and AS-2 was estimated at approximately 4.7 and 4.9 psig, respectively. The observed breakthrough pressures for AS-1 and AS-2 were 12 and 24 psig respectively. These pressures are within an acceptable range, which is above the minimum pressure required to overcome the saturated zone thickness above the sparge point and well below the overburden pressure of the formation of 77 psi for both AS-1 and AS-2. 5.2 Injection Flow Stable pressure and flow readings are indicative of a permeable injection zone where a relatively uniform flow field is quickly established (i.e., air does not need to take time to find preferential flow paths in the subsurface). During low, medium and high-flow testing at AS-1, the injection flow rates and pressure readings maintained at an average of approximately 5 scfm at 8 psig, 10 scfm at 10 psig and 20 scfm at 12.5 psig, respectively. During low, medium and high-flow testing at AS-2, the injection flow rates and pressure readings maintained at an average of approximately 2 scfm at 11 psig, 7.5 scfm at 14 psig and 15 scfm at 15 psig, respectively. 5.3 Pressure Response During injection testing at AS-1 and AS-2, positive pressure responses were observed in observation wells OBS-1 and VW-1. Additionally, induced pressure in the observation wells (following each injection test) returned to measured background levels (0 "H20) within approximately 45 minutes. Studies indicate that when induced vadose zone observation well pressures rapidly decrease (dissipate to background conditions in less than 2 days), air distribution in the saturated zone (in the test area) is relatively homogenous (R.L. Johnson, 1999). The rapid rate of pressure dissipation measured in the observation wells during the AS tests indicate that the air distribution in the saturated zone is relatively homogenous. 5.4 Groundwater Level Changes Apparent displacement was observed in observation wells OBS-1, AS-1, AS-2 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 MW-5 showed no apparent change in groundwater level response during AS-2 testing but did show a positive response during each step of AS-1 testing. After an initial increase in groundwater level in response to both initiation and changes in flow rate, the groundwater levels quickly returned to background levels for the duration 5-1 The Source Group, Inc.