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Mr. Barton • • January 9, 2015 Page 3 of 5 carbon (GAC) wellhead treatment system (SGI, 2013). Quarterly groundwater samples are collected from the treatment system to ensure GAC effectiveness. During the first quarter 2014, SGI advanced one Cone Penetration Technology boring (CPT-1) and collected grab groundwater samples at 4-foot intervals to the maximum depth explored of 160 feet bgs. Petroleum hydrocarbon compounds were detected in all groundwater samples collected between 121 and 148 feet bgs. The maximum TPHg concentration of 360 pg/L was detected in samples CPT-1-(121-125') and CPT-1-(127-131') (SGI, 2014). The extent of 1,2-DCA is not defined in groundwater down-gradient of the domestic well located at 10967. This Work Plan has been prepared with the objective to characterize the vertical extent of petroleum hydrocarbon impacted groundwater down-gradient of domestic well 10967. PRE-FIELD ACTIVITIES To meet the objective, the following pre-field activities will be completed: • Approval of this Work Plan will be obtained from the CRWQCB; • A Site-specific health and safety plan (HASP) will be updated in accordance with Occupational Safety Health Administration regulations 29 CFR 1910.120; • Revise the existing access agreement to include proposed investigation activities; • The proposed CPT boring locations will be demarcated on the Site and Underground Services Alert will be notified at least 48 hours prior to drilling to clear underground utilities in proposed drilling locations; • Soil boring permits will be obtained from the San Joaquin County Department of Environmental Health (SJCDEH); • SGI will retain a private utility locator to clear the proposed boring locations of other possible subsurface obstructions; and • The SJCDEH, and other necessary parties will be notified of proposed field schedule at least three days prior to initiating field work. CPT BORING AND GRAB GROUNDWATER SAMPLING In a January 15, 2014 electronic letter from the CRWQCB, a transect line of borings was requested down-gradient of domestic well 10967 to address recent video evidence that the domestic well is open from 60 to 129 feet bgs. To address this request, SGI will supervise the completion of four CPT borings (CPT-2 through CPT-5) located down-gradient of domestic well 10967 at the locations shown on Figure 2. Borings will be completed using a CPT direct push rig operated by a California C-57 licensed drilling contractor. Prior to boring advancement, the locations will be cleared to five feet bgs with a hand-auger. Subsurface lithologic and pore pressure data will be continuously recorded in the CPT sounding at approximately 2-inch (5 cm) intervals to develop a continuous record of soil stratigraphy and an estimation of hydrogeological properties. The Source Group,Inc.