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UST SYSTEM REMOVAL AND REPLACEMENT REPORT <br />Introduction <br />January 22, 2021 <br />1 .0 INTRODUCTION <br />This report documents underground storage tank (UST) system removal and replacement activities conducted at <br />7-Eleven Store No.20632 located at 4627 Da Vinci Drive in Stockton, California (Figure 1). These services were <br />conducted in accordance with the requirements of the San Joaquin County Environmental Health Department(EHD). <br />Stantec Consulting Services Inc. (Stantec)conducted soil sampling and observed tank removal activities. LC <br />Services was subcontracted by 7-Eleven, Inc. (7-Eleven)to conduct the UST removal and replacement activities. <br />1.1 PURPOSE AND SCOPE OF SERVICES <br />Stantec observed the removal of two existing USTs, the dispenser islands and the associated product and vent line <br />piping. Stantec collected soil samples to assess subsurface conditions beneath the former UST area, dispenser <br />islands, and product piping. Stantec's scope of services consisted of the following tasks: <br />Preparation of a site-specific Health and Safety Plan; <br />Observation of the UST removal activities; <br />Collection of soil samples beneath the USTs, dispenser islands, and product piping at the direction of the <br />EHD specialist; <br />Coordination of laboratory analysis of soil samples collected; and <br />Preparation of this report documenting the UST removal activities. <br />1.2 BACKGROUND <br />A previous environmental case was opened in February 1997 and closed in June 2014. Between February 1997 and <br />January 2005, seven groundwater monitoring wells,two air sparge/vapor extraction wells, and 18 soil borings were <br />drilled and installed as part of the environmental investigation. Quarterly groundwater monitoring, sampling, and <br />reporting was implemented First Quarter 1998. <br />In October 1998, UST removal and replacement activities were conducted at the site. Fourteen soil samples were <br />collected beneath the USTs, dispenser island and vent lines. Maximum benzene, total petroleum hydrocarbons as <br />gasoline (TPHg), and methyl-tert-butyl ether(MTBE)concentrations in soil samples were 4.3 milligrams per kilogram <br />mg/kg), 2,100 mg/kg, and 26 mg/kg, respectively. One grab groundwater sample was collected from the UST <br />excavation and two groundwater samples were collected from the on-site water storage tanks. Maximum benzene, <br />TPHg, and MTBE concentrations in groundwater were 770 micrograms per liter(Ng/L), 80,000 pg/L, and 30,000 tag/L, <br />respectively.Approximately 967 tons of soil and 92,000 gallons of groundwater were transported for disposal during <br />UST replacement activities. In April 2003,fuel dispensers and product piping were removed and replaced.Two soil <br />samples were collected beneath the southern fuel dispenser and product line trenching. Benzene,TPHg, and MTBE <br />were detected at maximum concentrations of 0.019 mg/kg,4.7 mg/kg, and 0.60 mg/kg, respectively. <br />us0385-ppfss01\workgroup\1858\active\185851012\05_report_deliv\deliverable\reports\2021_rpt_20632_ust.docx