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Former Countryside Market, Stockton,California Feasibility Study and Interim Remedial Action Plan May 20,2013 In addition to proposed observation well OBS-1, existing monitoring well MW-2 will be utilized as a primary observation point. OBS-1 will be located approximately 7.5 feet and 15 feet from AS-2 and AS-1, respectively, and AS-1 will be located approximately 22.5 feet from MW-'A',. Other existing monitoring wells that surround this testing area (i.e., MWA, MW-3, MW-4 and M -5) will also be part of the observation well network. This testing configuration allow for sparge influer ce monitoring in at least two directions from the injection well(s). As shown on Figure 4, the two proposed AS test wells will be installed within and/or in close proximity to the former UST area just inside the northern property boundary of the Site. The locations and configurations of the proposed ells have been selected to target this key area of the Site. Further feasibility testing details are provided below. 5.1.1 Pre-Field Activities Prior to performing the sparge and observation well installation field work, the following activities will be completed: ➢ Approval to proceed with the work will be obtained from the CRWQC{B; ➢ Well permits will be obtained from the San Joaquin County Environmental Health Department (SJCEHD); ➢ Drilling locations will be demarcated at the Site; ➢ Proposed drilling locations will be cleared of underground utilities by Underground Service Alert (USA) of Northern California; ➢ A private utility contractor will clear each drilling location for undergr and utilities; ➢ A Site and task-specific health and safety plan (HASP) will be pre ared/updated in accordance with OSHA regulations 29 CFR 1910.120; and ➢ The CRWQCB and other necessary parties will be notified of proposed field activities at least seven days (as feasible) prior to initiating fieldwork. 5.1.2 Drilling and Well Installation Details SGI will supervise the drilling, soil sampling, and installation of the sparge and observation wells (AS-1, AS-2 and OBS-1), and vapor well (VW-1). The test wells will likely be con ipleted using a CME-85 high- torque truck-mounted drill rig (or equivalent) equipped with 6-inch and 8-inch diameter augers and operated by a California-licensed drilling contractor. Drilling supervision, soil sampling, and lithologic descriptions will be completed by an experienced field geologist/scien iist working under the direct supervision of a California Professional Geologist. Prior to drilling, the locations will be cleared of obstructions/utilities by h nd-augering and post-holing to five feet bgs. The augers will be pressure washed to prevent cross contamination from previous drilling events. Observation well OBS-1 will be continuously cored from approximately 15 feet bgs to total depth to provide for a complete vertical characterization of soil impacts in the former UST area. re ibllAySNyantlFmbilRy6RMy&IRAP-Te Fmel,da 5-2 The Source W800,101C.