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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 samples were collected using low-flow sampling techniques with dedicated polyethylene tubing at each location. Water quality parameters were measured and recorded during the groundwater sampling event to ensure the groundwater samples were representative of aquifer conditions Groundwater samples were transferred directly into laboratory-supplied containers and placed on ice for transport to Moore Twining Associates, Inc. of Fresno, California under strict COC. The observation well field sampling forms are included as Appendix F. Pre-pilot test groundwater samples were analyzed for TPHg by USEPA 8015B, BTEX, 7- oxygenates and lead scavengers by USEPA Method 8260B, carbon dioxide by SM-4500-CO2C, methane, ethane, ethene by RSK-175M, dissolved iron, iron and manganese by USEPA 200.7, total organic carbon by SM5310B, chloride, nitrate, and sulfate by USEPA 300.0, fatty acids by HPLC/UV, and chloride by USEPA 300.0. Post pilot test samples were analyzed for TPHg by USEPA 8015M and BTEX, 7-oxygenates, and lead scavengers by USEPA 8260B. Soil vapor samples were collected using sample ports on the well caps and Tedlar® bags. Teflon ® tubing was used to create an airtight connection between the well to a Tedlar® bag inside of a vacuum box. A hand-operated vacuum pump was connected to the vacuum box, and the air was evacuated from the vacuum box, resulting in the Tedlar® bag inflating with soil vapors evacuated from the well. New Teflon® tubing was used at each observation well location. Soil vapor samples were transferred into enclosed box containers and transported to American Analytical of Chatsworth, California under strict COC. All soil vapor samples collected before and after pilot test activities were analyzed for TPHg, BTEX, 7-Oxygenates, and lead scavengers by USEPA Method 8260B Groundwater and soil vapor sample analyses were performed appropriately as requested on the COC. All analytical holding times for the analyses were met by the laboratory. Laboratory quality control parameters indicate precision and accuracy for all methods employed. No data was rejected. The data are considered valid, representative, and adequate for decision making purposes. 4.2.2 Monitoring and Sampling Results SGI collected pre- and post-pilot test groundwater samples from wells AS-1, AS-2, and CBS-1 on January 13 and 29, 2015, respectively. Results indicate all petroleum related constituents generally decreased significantly by approximately an order of magnitude between sampling events with the exception of EDB and 1,2-DCA in OBS-1. Petroleum hydrocarbon results are presented in Table 5 and displayed on Figure 4. General chemistry results are presented on Table 6. Laboratory analytical reports are included in Appendix E. SGI collected pre- and post-pilot test soil vapor samples from VIN-1 and CBS-1 on January 19 and January 28, 2015, respectively. Results indicate all petroleum related constituents decreased between sampling events. Soil vapor results are presented in Table 7. Laboratory analytical reports are included in Appendix E. 4-2 The Source Group, Inc.