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Mr. Siddharth Sewalia August 10, 2017 Well Destruction Activities The wells are not located in an area of known or suspected soil contamination therefore destroying the wells by pressure grouting is appropriate. Arcadis will supervise Cascade Drilling L.P. of West Sacramento, California (a C-57 California State-licensed driller) to destroy six wells (EW-04, EW-04A, PW08-076, PW08-155, PW08-180, and INJ-14) included in the MRP (Figure 3). The total depth will be measured and compared to the existing well construction information prior to destroying each well. Well construction information is summarized in Table 1 and presented in boring logs in Attachment A. If debris is present in a well, it will be removed by the driller. A hole 1-foot larger in diameter than the well diameter will be cleared to a minimum 3-feet below ground surface (bgs) using an air-knife. The well casing will then be cutoff at 2.5-feet bgs. INJ-14 will be cleared to 6-feet bgs and the casing will be cutoff at 5.5-feet bgs due to the planned development. Neat cement will then be pumped into the well casing via a tremie pipe placed near the bottom of the well and raised to the surface as the grouting progresses. A pressure of 25 pounds per square inch will be maintained on the grout for 5-minutes prior to raising the tremie pipe. The volume of grout placed will be calculated to confirm it exceeds the casing volume of the well being destroyed. Grout will be allowed to mushroom over the top of the casing and into the excavated borehole around the casing to 1-foot above the base of the excavated borehole. The remainder of the borehole will be filled with imported fill to grade to match existing conditions. Well destruction activities will be recorded on a Well Destruction Log (Attachment B). Following monitoring well destruction activities, Water Well Completion Reports will be filed with the California Department of Water Resources (DWR) and with the City of Lathrop. Conveyance Piping and Electrical Conduit Removal Arcadis will supervise a qualified contractor to remove existing conveyance piping and electrical conduit that is associated with EW-04, EW-04A, and INJ-14. The trenching will be completed with approved heavy equipment, and the area will be excavated so that all appropriate activities can take place. After all piping and conduit is removed, the trench will be filled with imported fill to grade as appropriate. Investigation Derived Waste Management Water generated during destruction activities will be processed at the on-site waste water treatment plant. Piping and electrical conduit removed during destruction activities will be transported off-site for disposal by a licensed waste hauler. REPORTING AND SCHEDULE A report detailing the well destruction activities will be prepared to document the proposed work. The well destruction report will include a summary of the well destruction field activities, copy of the approved permit, copies of the DWR Water Well Completion Reports, and well destruction logs. Arcadis will begin coordinating well destruction activities as soon as this Work Plan is approved by the Regional Water Quality Control Board. Well destruction and piping removal is to be completed by the end of September 2017 to prepare the property for development. arcadis.com Page: Lathrop Well Destruction Work Plan (8.10.2017).docx 3/4