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California Water Service Co an Y Final Closure Report for Underground Storage Tank Removal 1602 E. Lafayette St., Stockton, CA FINAL CLOSURE REPORT TWO UNDERGROUND STORAGE TANK SYSTEMS CALIFORNIA WATER SERVICE COMPANY 1602 E. Lafayette Street Stockton, CA 95205 1.0 EXECUTIVE SUMMARY Chow Engineering, Inc. (CE) has completed the closure activities associated with the removal of two (2) previously unknown underground storage tanks (USTs) at the California Water Service Company (Cal Water) facility at 1602 E. Lafayette Street, Stockton, CA (site). This report documents the closure activities performed at the site. The tanks and associated piping have been closed per the Closure Permits issued by the San Joaquin County Environmental Health Department (County or SJCEHD) and City of Stockton Fire Department (Fire Department), Work Plans, and the Site Health and Safety Plan developed by CE. The closure activities began in December 2011 and ended in January 2012. The tasks performed included: 1) removal of the residual tank contents, 2) excavation, removal, transportation, and disposal of the USTs at a permitted facility in Richmond, CA, 3) tracing and removal of associated pipelines up to the adjacent building, 4) confirmation soil sampling at the tank excavation and along the associated piping, 5) closure in place of three short segments of piping under the building foundation, 6) backfill of the excavation, 7) disposal of waste generated during the closure and 8) preparation of this final closure report. On January 10, 2012, the SJCEHD and Fire Department performed the final inspection of the closure and verified closure activities were completed. 2.0 CLOSURE ACTIVITIES Two (2) USTs, each approximately 8,500 gallons in capacity, were discovered to be present at the site at 1602 E. Lafayette Street, Stockton, CA in October 2011 (Figures 1 and 2, Appendix A). The USTs were apparently installed during the 1930s. The USTs had been taken out of service sometime ago by a previous owner and one was discovered filled with sand while the other was partially filled with water (sand in Tank#1 and water in Tank#2). Both tanks had been used as fuel oil tanks for fuel oil supply to the boiler house nearby. Tank#1 had a heel (3 to 4 inches) of fuel oil in the bottom below the sand while Tank#2 also had a heel after the water was removed. Based on field observations and the former equipment located in the building where the pipelines ran, the USTs are believed to have contained Bunker C fuel for boilers that were previously housed ' in the adjacent building. CHOW ENGINEERING, INC. 1