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Nana 5.1 Permitting and Access The required permits will be obtained from the San Joaquin County Environmental Health Department and from the City of Stockton. Additionally, Phillips 66 is currently negotiating an access agreement with the property owner to the north of the site to perform groundwater monitoring well installation activities. 5.2 Underground Utility Clearance GHD will mark out the proposed well locations, contact Underground Service Alert(USA), and hire a private utility locator prior to drilling to identify any utilities in the proposed well locations. 5.3 Health and Safety Plan GHD will prepare a site health and safety plan to protect site workers and visitors. The plan will be reviewed and signed by all site workers and visitors, and kept onsite at all times during work activities. 5.4 Monitoring Well Borehole Advancement Prior to initiating drilling activities, all proposed monitoring well locations will be cleared to a minimum of 5 fbg with an air knife to further mitigate potential damage to underground utilities. The proposed monitoring wells will be advanced using 8-inch diameter hollow-stem augers. The two B Zone wells will be advanced to a total depth of approximately 83 fbg and the C Zone well will be advanced to a total depth of approximately 118 fbg. 5.5 Monitoring Well Construction The monitoring wells will be constructed with 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing with approximately 15 feet of 0.020-inch slotted PVC screen. The screen interval for the B Zone wells will be set from approximately 68 to 83 fbg and from approximately 103 to 118 fbg for the C Zone well. The filter pack will consist of 2/12 Monterey Sand that will be placed in the annular space between the borehole wall and the well casing from the total depth to approximately two feet above the screened interval. A two-foot thick hydrated bentonite seal will be placed above the filter pack. The overlying sanitary surface seal composed of Portland Type 1/11 neat cement will placed above the hydrated bentonite to approximately 1 fbg. The monitoring wells will be finished and secured using a locking cap inside a traffic-rated well box finished flush with the ground surface. Boring depth and well construction details may be modified based on subsurface conditions encountered during drilling. 5.6 Soil Sampling Soil samples will be collected at least every five feet from each well during drilling activities to characterize subsurface soils and for possible chemical analysis. Each sample will be field screened using a photoionization detector(PID) and logged in accordance with ASTM Standard 2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure, Unified Soil Classification System). Additional soil samples may be collected at lithologic changes or near the water table. Samples exhibiting elevated PID readings or physical signs of residual GHD I Well Installation Work Plan Addendum 111193145(5)1 Page 4