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Geosynte& <br /> consultants <br /> 1. INTRODUCTION <br /> Geosyntec Consultants, Inc. (Geosyntec) has prepared this Final Investigation Work Plan <br /> Addendum— UST 817E (Revised Work Plan Addendum) on behalf of the Port of Stockton(Port), <br /> regarding the former underground storage tank(UST) 817B located at Rough and Ready Island <br /> (RRI), Port of Stockton(Figure 1), to address comments received from the Central Valley <br /> Regional Water Quality Control Board(CVRWQCB) on December 16, 2021, on the Draft <br /> Investigation Work Plan Addendum— UST 8178. A response to the CVRWQCB's comment <br /> letter is included in Appendix A. Responses have been incorporated throughout this Revised <br /> Work Plan Addendum. <br /> This Revised Work Plan Addendum presents a field investigation to characterize petroleum <br /> constituents in soil and groundwater and to assess the potential presence of light non-aqueous <br /> phase liquid(LNAPL) within the former UST 817B excavation area (the Site). This work is an <br /> addendum to the Final UST Data Gap Investigation Work Plan— UST Sites 605, 517, 916B, and <br /> 817E (Final UST Work Plan; Geosyntec, 2019a; Appendix B). <br /> This work will be completed under the July 30, 2003, Consent Agreement, which the Port <br /> entered into with the State of California, California Department of Toxic Substances Control <br /> (DTSC), and the CVRWQCB for RRI. DTSC is the lead regulatory agency and the CVRWQCB <br /> is the supporting agency for environmental work at RRI, except with respect to petroleum USTs <br /> and petroleum contaminated sites, for which the CVRWQCB is the lead regulatory agency and <br /> DTSC is the supporting agency. UST 817B is a petroleum UST site; therefore, the CVRWQCB <br /> is the lead regulatory agency. <br /> 1.1 Purpose and Objectives <br /> In 2019, Geosyntec conducted a soil and soil vapor investigation that identified elevated <br /> concentrations of petroleum constituents, primarily total petroleum hydrocarbons as gasoline <br /> (TPH-g), and benzene, ethylbenzene, toluene, and xylenes (BTEX), in soil vapor around the <br /> former UST excavation area. The objective of this investigation is to characterize the soil and <br /> groundwater within the former UST excavation and assess the potential presence of LNAPL <br /> within the former UST 817B excavation area. This information will be used to evaluate the <br /> potential source of the elevated petroleum constituents detected in soil vapor in 2019. <br /> The scope of work for the additional subsurface investigation is described below. <br /> 1.2 UST 817B Background <br /> Building 817B was a former open-air fueling station that housed two fuel dispenser pump islands <br /> and a vehicle wash rack. Fuel was stored in four USTs (Figure 2). These USTs reportedly <br /> contained gasoline and kerosene. The tanks, pumps, and associated piping were reportedly <br /> removed prior to 1997, and Building 817B was demolished in 2007. The UST removals were <br /> documented in the Underground Storage Tank UST 817E-2, Tank Removal Summary Report <br /> (PRC Environmental Management, Inc. [PRC], 1993) and the UST Closure Report(Smith <br /> Technology Corporation, 1996)prepared on behalf of the United States Navy. <br /> Final Investigation Work Plan Addendum—UST 817B I June 24,2022 <br />