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2022 monitoring and sampling event are included in Appendix C. C-zone hydrocarbon isoconcentration contour maps and rose diagram for the same event are included as Appendix D. Further details of the proposed scope of work are discussed below. 5.1 Permitting and Access The required drilling permits will be obtained from the San Joaquin County Environmental Health Department along with an encroachment permit from the City of Stockton. 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 underground utilities in the vicinity of 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 kept onsite at all times and reviewed and signed by all site workers and visitors prior to beginning work. 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 underground utility strike risk. The proposed monitoring wells will be advanced using 8-inch diameter hollow-stem augers. The B-zone monitoring well will be advanced to a total depth of approximately 80 fbg and both the C-zone monitoring well and sentry well will be advanced to a total depth of approximately 120 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 well will be set from approximately 65 to 80 fbg and from approximately 105 to 120 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. The filter pack will extend from approximately two feet above the top of the screen to the total depth of the well and will be sealed with a two-foot layer of hydrated bentonite. The overlying sanitary surface seal, composed of Portland Type 1/II neat cement, will fill annular space above the hydrated bentonite seal 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. Well construction details may be modified based on subsurface conditions encountered during drilling. 5.6 Soil Sampling Samples will be collected every five feet from each boring during monitoring well installation to characterize the subsurface soil. Additional soil samples may be collected at lithologic changes or near the water table. 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). Samples exhibiting elevated PID readings or physical signs of residual hydrocarbon impact will be submitted for laboratory analysis. Soil samples will be collected using Terra Core®samplers to transfer soil into laboratory supplied containers. The containerized samples will be labeled, entered onto a chain- of-custody form, packed on ice, and sent to Eurofins Test America (Test America) of West Sacramento, California for analysis. 5.7 Laboratory Analysis Soil samples submitted to Eurofins Test America for laboratory analysis will be analyzed for the following: • TPHg by EPA Method 8260B GHD I Phillips 66 112594700 1 Offsite Investigation Work Plan 4