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Work Plan for Groundwater Monitoring Well Installation, Soil Gas and Groundwater Investigation, and Groundwater Monitoring Army Aviation Support Facility, Stockton, California • 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, 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 AASF WASH RACK GROUNDWATER AND SOIL GAS INVESTIGATION After all site preparation activities are complete, grab groundwater and a soil gas sampling will be conducted at approximately 30 locations. Approximately 27 locations are proposed in the vicinity of the former wash rack, existing/former USTs, and along the surficial drainage area continuing to the east along the southern site boundary. These locations include four borings at the proposed locations of the groundwater monitoring wells (see Section 3.4). Additionally, two borings are proposed adjacent the AASF shop and one boring adjacent the existing wash rack clarifier. The approximate locations of these borings are indicated in Figure 4. The primary objective of this investigation is to evaluate potential impacts and migration pathways in groundwater and soil gas associated with potential sources of VOCs (including TCE) near the former USTs. The data from the grab groundwater and soil gas samples will be compared with applicable California and Federal health-based standards to assess the potential for impacts to human health and/or the environment. 3.3.1 Grab Groundwater Sampling As indicated above, approximately 30 soil boring locations are proposed for the purpose of collecting grab groundwater samples. Using direct-push technology, two borings will be advanced at each of the proposed boring locations indicated in Figure 4. The first direct- ush boring at each location will be advanced to first occurrence of groundwater for co ection of a grab groundwater sample using a HydropunchTm tool, or similar technology. Soils will be cored continuously to provide a detailed analysis of lithology for logging purposes, and to determine an appropriate well screen interval for soil gas sample collection. A photoionization detector a (PID)will be used to screen the cored soils for VOCs approximately every foot. In an offset location adjacent to the first borehole, a second direct-push boring will be advanced for the collection of soil gas samples, as described below. Grab groundwater samples will be collected in sterile, laboratory-supplied containers, submitted to a California-certified laboratory under appropriate COC documentation, and analyzed for the following: • TPH-g and TPH-d using USEPA Method 8015-Modified; • VOCs, including Naphthalene, BTEX, and Fuel Oxygenates using USEPA Method 82606; and • Total Lead using USEPA Method 6010B. OTIE 8