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Mr. Robert Fagerness 11 March 2026 Page 3 groundwater monitoring programs, as described herein, is being completed in a phased manner to facilitate decommissioning of Site remedial infrastructure before July 1, 2030. The following section presents the evaluation conducted in support of this well destruction notification and request to modify the groundwater monitoring programs for the Site. EVALUATION SUMMARY There are over 100 piezometers,groundwater monitoring,extraction,and injection,and other types of wells that have historically been used to support implementation of various phases of soil and groundwater remedial action and performance assessment at the Site. To advance the Site towards completion of the current groundwater remedy and eventual decommissioning of remedial infrastructure, the Trust is iteratively decommissioning wells present at the Site that no longer provide benefit in performing or assessing the remedy (Table 1 and Figure 1). To inform the selection of wells for destruction, a Well Destruction Decision Tree(Decision Tree) was developed (Work Plan; Appendix A). The Decision Tree provides a framework for the destruction of all types of Site wells in the future,as the remedy progresses and meets the remedial objectives described in the Site Response Plan. Site wells and piezometers, including all locations listed within the GWMP and WDR-MRP, were screened using the Well Destruction Decision Tree. Three former groundwater extraction wells which are no longer in use were also screened. A total of 45 groundwater wells and piezometers have been identified and proposed for destruction in accordance with the Work Plan as summarized in Table 2. Additionally, in accordance with the approved Soil and Soil Vapor No Further Action Request, soil vapor extraction is no longer implemented at the Site and the two existing soil vapor extraction wells and triple-nested soil vapor probe were identified for destruction and will be destroyed in accordance with the Work Plan. Furthermore, GWMP and WDR-MRP monitoring locations that were not selected for destruction were reviewed for sufficiency or excessiveness. Table 3 presents proposed modifications to the GWMP and WDR-MRP. The GWMP monitoring locations are sampled for volatile organic compounds (VOCs) or gauged for water level on a semi-annual to biennial frequency. Beyond the GWMP wells proposed for destruction (Table 2), the analyte list and monitoring frequency continues to support remedial Geosyntec.2024.Soil and Soil Vapor No Further Action Request,Lincoln Center,Stockton,California.5 December. engineers I scientists I innovators