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Geosyntec c�' consultants 1. INTRODUCTION Geosyntec Consultants Inc. (Geosyntec) has prepared this Work Plan for Destruction of Damaged Monitoring Wells and Installation of Replacement Monitoring Wells (Work Plan) on behalf of Glenn Springs Holdings,Inc.and J.R. Simplot Company to describe the proposed destruction of two damaged monitoring wells and their replacement at the former agricultural chemical distribution facility located at 1904 West Charter Way in Stockton, California (the Site). This Work Plan was prepared in accordance with the Standard Requirements for Monitoring Well Installation Workplans and Monitoring Well Installation Reports(California Regional Water Quality Control Board, March 2012). This Work Plan includes pertinent site background information (Section 2), the objectives and scope of work (Section 3), methods to be used to destroy the wells and install their replacements (Section 4), changes to the groundwater monitoring program to incorporate the new wells(Section 5),and a schedule for the work and associated reporting(Section 6). 2. SITE BACKGROUND The Site occupies approximately 4.2 acres in a predominantly industrial area west of the City of Stockton, California(Figure 1).A residential neighborhood borders the Site to the east, an undeveloped parcel borders the Site to the south, and parcels located immediately west and north of the Site are used for industrial purposes. The San Joaquin River and Stockton Regional Wastewater Disposal Ponds are located approximately 3,000 and 3,500 feet west of the Site, respectively. The Site was used from 1955 to 1993 for storage and distribution of agricultural chemicals, including pesticides, herbicides, soil fumigants, and fertilizers containing nitrogen and other plant nutrients. This entailed the use of structures including a multi-purpose building,tank farms,storage bunkers and wash racks. Gasoline and diesel fuel, used to fuel delivery trucks,were stored in underground tanks near the east side of the multi- purpose building and were removed in 1990. The Site is currently vacant and fenced around its entire perimeter. Concrete slabs and structural foundations for other former Site infrastructure remain in some areas of the Site. Previous investigations indicate that the Site is underlain by relatively continuous thin layers of sand, silt and clay to a depth of about 150 feet below ground surface (ft bgs). The upper 16 to 20 feet are fine-grained materials with a relatively continuous fine-to medium-grained sand interval occurring between about 20 and 40 ft bgs. Sand intervals were also identified at 60, 80 and 100 ft bgs. Groundwater monitoring wells have been installed on-Site and in the adjacent residential area to monitor the shallow(20 to 40 ft bgs)and intermediate (70 to 90 ft bgs) groundwater zones. Groundwater levels vary seasonally at the Site with levels declining during the summer months and recovering during the winter months. Groundwater level data for the past 10 years of monitoring show that the water level in the shallow zone varied OxyChem-Stockton MW Replacement Work Plan 7.18.25 1 2025.07.18