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Soil Boring Results and VEG/ISCO Work Plan Field Maintenance Shop #24, Stockton, California October 2016 The primary objective of in-situ VEG implementation is to reduce vadose zone source impacts and limit petroleum contaminants from leaching and contributing to groundwater concentrations at the Site. A secondary objective, is to evaluate the effectiveness of in-situ application of VEG technology as a remediation alternative for other ARNG contaminated sites. 3.2.2. Proposed VEG Scope Prior to any VEG subsurface activities, utility clearances will be performed at the Site to avoid damaging subsurface assets. In addition, an underground service alert (USA) North 811 notification will be made 48-hours prior any subsurface activities. The VEG treatment area is centered around FMS-MW6 and shown in Figure 6. Prior to the VEG treatment, wells will be installed to implement both steam injection (2-inch diameter wells) and vapor extraction (4-inch diameter wells) within the target area. Injection/extraction wells will be constructed using stainless steel screens and temperature resistant grout. The wells will be installed by a licensed 0-57 well contractor. The number of wells and spacing will be determined in the field based on initial radius-of-influence (ROI) testing. The VEG wells will be installed at least two (2) weeks prior to initiation of VEG treatment, allowing for temperature resistant grout to sufficiently cure prior to steam injection. After the installation of the VEG wells, the Remedial Contractor will mobilize all equipment and resources necessary to perform in-situ VEG thermal treatment of petroleum hydrocarbons in the target treatment area in the vicinity of monitoring well FMS-MW6 (Figure 6). Specifically, treatment across a 20-foot by 20-foot surface area centered at FMS-MW6 and along a vertical profile of 15 to 35 feet bgs is proposed corresponding to an estimated volume of 300 cubic yards. The VEG in-situ treatment is expected to occur over a 2 to 3-week period, depending on how rapidly the site-specific soils (and inherent soil moisture) thermally respond to the steam injection, as measured by how quickly the temperature of the targeted soils increase by 200 to 300 degrees Fahrenheit (°F) relative to ambient levels. The steam injection activities will be accompanied by approximately one week of soil vapor extraction, overlapping steam injection and soil vapor extraction during the last week of steam injection. Upon completion of VEG steam injection and treatment activities, the VEG wells will be abandoned. Well abandonment will consist of over-drilling and removal of the top three (3) feet of well casing, followed by grouting in place of the remaining portions of the casings per SJCEHD requirements. 3.2.3. VEG Soil Confirmation Sampling Upon completion of well abandonment activities, soil confirmation borings will be advanced within treatment area, allowing for post-treatment soil sampling to take place within the specified vertical profiles subjected to treatment. Up to three (3) soil borings will be advanced in the treatment area and soils will be field screened utilizing a photoionization detector (PID). At a minimum soil samples will be collected at 5 foot intervals from 15 to 35 feet bgs and at locations exhibiting any PID responses greater than 100 parts per million (ppm) from field screening. Soil samples will be submitted to BC Labs for the following analyses: VOCs and Naphthalene by EPA method 8260B; Total petroleum hydrocarbons as gasoline (TPH-g) by EPA method 8260B; and Total petroleum hydrocarbons as diesel TPH-d by EPA method 8015B. Page 7