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UST SYSTEM REMOVAL AND REPLACEMENT REPORT Field Activities January 22, 2021 3.0 FIELD ACTIVITIES 3.1 UST REMOVAL AND REPLACEMENT ACTIVITIES On December 1,2020, Stantec observed the removal of two 10,000-gallon single-walled steel USTs at the site. The USTs were triple rinsed on site and were approved for removal by the EHD.The tanks were transported to West Coast Equipment in Turlock, California for destruction and disposal.The rinsate manifest and disposal documentation for the USTs are provided in Appendix A. On December 4,2020, LC Services installed two new USTs: one chambered 20,000-gallon double-walled fiberglass UST, and one 20,000-gallon double-walled fiberglass UST.The USTs were installed in an expanded tank excavation located in the eastern portion of the site. The UST overburden soil was stockpiled during the UST removal activities. From December 3 through December 17, 2020, approximately 935 tons were transported as clean fill to Waste Connections, Potrero Hills Landfill in Suisun, California for disposal. Bills of lading and non-hazardous soil manifests for the soil removed are included in Appendix B. 3.2 EXCAVATION DEWATERING AND DISPOSAL Groundwater was encountered within the excavation during tank replacement activities at approximately seven feet below ground surface(bgs).To facilitate UST removal and installation,dewatering of the tank basin was required. On November 10, 11, and 18, 2020, approximately 13,200 gallons of water were removed via vacuum tracks and the water was transported to Instrat Inc. in Rio Vista, California for treatment and disposal. Manifests are presented in Appendix B. On behalf on 7-Eleven, Stantec obtained approval from the City of Stockton Municipal Utilities Department to discharge to the City of Stockton stormwater system. The approval allowed for the setup of a construction dewatering system with the required pre-treatment equipment,which allowed groundwater discharge directly into the stormwater system. Upon approval, LC Services contracted Griffin Dewatering LLC to setup the dewatering and pre- treatment system. LC Services operated and maintained the system during UST removal and installation activities. From November 23,2020 through December 7, 2020, approximately 1,100,683 gallons of groundwater was pumped, treated, and discharged into the stormwater system under the City's approval. 3.3 SOIL SAMPLING ACTIVITIES On December 1,2020, Stantec personnel collected seven soil samples under the direction of the San Joaquin County EHD. Soil samples were obtained at approximately four feet bgs beneath the former dispenser islands and product piping, and at approximately 14.5 to 15.5 feet bgs in the UST excavation.The soil samples were collected from the excavator bucket. The soil samples were immediately placed in clean laboratory supplied glass jars. Each jar was completely filed to minimize headspace and sealed with a Teflon lined screw cap. Each sample was labeled and placed on ice in a cooler. us0385-ppfss01\workgroup\1858\active\185851012\05_report_deliv\deliverable\reports\2021_rpt_20632_ust.docx 3.1