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• 0 Work Plan for Groundwater Investigation and Groundwater Monitoring Well Installation Field Maintenance Shop #24, Stockton, California 3.0 PROPOSED ACTIVITIES This section describes the specific activities associated with the implementation of the scope of work described in Section 1.1, Project Objectives and Scope. All proposed field activities will be conducted in accordance with the APP/SSHP (submitted under separate cover). 3.1 PERMITTING The San Joaquin County Environmental Health Department (SJCEHD) is the lead agency that oversees drilling activities within San Joaquin County. In accordance with SJCEHD requirements, a single well permit application will be filed for the 15 proposed MIP borings and three proposed groundwater monitoring wells. Once all appropriate SJCEHD permits have been received, field activities will be scheduled. 3.2 SITE PREPARATION All proposed field activities will be coordinated in advance with the CVRWQCB and appropriate CA ARNG personnel. Site preparation activities will be coordinated by OTIE's Field Manager, and will be initiated by a site visit to mark out proposed invasive drilling locations (i.e. MIP boring and well locations). The Field Manager will further ensure that those locations are cleared for underground utilities or other obstructions. This clearance will include: • Reviewing with CA ARNG personnel available site drawings indicating the approximate locations of all underground utilities (e.g., water, sewer, telecommunications, cable television, electric, and gas) associated with site operations, and making use of any anecdotal information that may be available through CA ARNG personnel familiar with site operations; • Marking the proposed locations with white spray paint; • Clearing the specific locations using a contracted private utility locator, who will use appropriate geophysical techniques to identify potential underground obstructions at those locations; and • Making appropriate notification to Underground Service Alert (USA) at least 48 hours prior to commencement of invasive drilling activities. 3.3 MEMBRANE INTERFACE PROBE BORINGS Following site preparation activities, 15 MIP borings will be advanced within an approximately 2,500 square foot area in the vicinity of the former USTs, representing the approximate primary source area. Previous investigations have identified this area as having the most significant impacts to soil and groundwater from petroleum hydrocarbons and related compounds (OTIE, 2010; 2012b). MIP borings are anticipated to be advanced to a depth of approximately 50 feet bgs. The approximate investigation area and the proposed MIP boring locations are depicted in Figure 4. MIP is semi -quantitative, total volatile organic screening tool used in conjunction with direct push drilling technologies (DPT). The MIP tool and detector system itself does not provide specificity of analytes. Rather, the MIP system is comprised of a differentially permeable membrane that is heated to a constant temperature, volatilizing organic contaminants as the MIP is advanced through the soil using the DPT rig. Clean carrier gas is circulated across the OTI E 10