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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 6.1 Air Sparge and Soil Vapor Extraction System Engineering Design The engineered AS and SVE system construction design and layout are included as Figures 6A through 6J which will be used for building, safety permitting and equipment procurement. The following sections detail system equipment components, installation, and construction. 6.2 Air Sparge Well Installation The proposed AS well network will consist of ten AS wells (including existing injection wells AS-1 and AS-2). Wells will be spaced along east to west transects that extend diagonally across the Site, generally perpendicular to the flow direction of groundwater. Wells are spaced on approximate 15 to 20-foot centers to provide for overlapping and comprehensive coverage, based on the conservatively estimated 15-foot AS zone of influence from the completed feasibility testing. Well locations are placed within the areal extent of the dissolved-phase hydrocarbon plume. The proposed AS well locations are shown on Figure 5A. Prior to drilling, the locations of all proposed AS wells will be cleared by USA, and then cleared to full auger width using a hand auger or post hole digger. All down-hole drilling equipment will be steam-cleaned to prevent cross-contamination from previous sampling events. AS wells will be constructed using 2-inch Schedule 80 PVC blank and screened (0.010-inch slot) casing. The well screen interval for each of the AS wells will be determined in the field based on the depth to the low permeable horizon. SGI anticipates that the AS wells will be screened from approximately 110 to 115 feet bgs with a 5-foot sump, similar to existing wells AS-1 and AS-2 (Figure 5B). The sparge wells will be installed using hollow stem auger or sonic drilling equipment. Annular seals above the screened intervals will consist of bentonite pellets/grout. Surface completion for the wells will consist of a flush-mounted, traffic-rated remediation well vault set in concrete. All soil cuttings, well development groundwater, and decontamination water generated during drilling and well installation will be contained and stored in U.N.-approved, 55-gallon drums for appropriate disposal via a licensed waste contractor. 6.2.1 Air Sparge Remediation Piping SGI will install pressure rated air hose, galvanized (above ground) and/or PVC (buried) piping to the proposed AS well locations. Conveyance piping (3/4 to 1-inch) will be buried in trenches and connected to a manifold within the rennediation compound. A dedicated pipe, or "homerun," will extend from the manifold in the compound to each well. Tie-in at the wellhead will consist of a tee- fitting to enable a threaded cap to be installed on the wellhead for future access for cleanout or gauging. 6-2 The Source Group, Inc.