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wood. surrounding area is primarily agricultural lands with some mixed-use light industrial and light density residential areas along South Banta Road (Figure 1). The Site produces sodium hypochlorite (liquid bleach) from chlorine and caustic soda, and its primary constituents of concern (COCs) are chloroform and carbon tetrachloride, which are present in low concentrations in groundwater. A detailed summary on the site background, site history, and previous investigations is provided in the Conceptual Site Model Report, Olin Chlor Alkali Facility, Tracy, California (CSM; Amec Foster Wheeler Environment & Infrastructure, Inc., 2017). 3.0 RATIONALE FOR DECOMMISSIONING GROUNDWATER MONITORING WELLS Olin will decommission monitoring wells MW-1, MW-3, MW-6, MW-7, and MW-16 (Figure 2). The rationale for decommissioning selected groundwater monitoring wells is summarized below and described in further detail in Proposed Revisions to Monitoring and Reporting Program R5-2012-0813 (Wood, 2021). MW-1 & MW-3 MW-1 and MW-3 have been dry since 2018. • Site COC concentrations have been decreasing or stable and have been below screening levels since 2016. MW-6 MW-6 was damaged by agricultural equipment and has not been sampled since March 2016. The CVWB has approved the sampling of MW-5 in place of MW-6 and requested that MW-6 be properly abandoned (CVWB, 2021). MW-7 & MW-16 MW-7 is cross-gradient to the historical source area, has only been used for groundwater elevations measurements, and was dry in 2021. MW-16 is cross-gradient to the historical source area and has not detected Site COCs since 2008. 4.0 DECOMMISSIONING METHODS Prior to decommissioning the wells, Wood will obtain appropriate county permits and coordinate with Union Pacific Railroad for access to the area. 2 https://woodplc.sharepoint.com/teams/OlinTracy/Shared Documents/General/03.0 DocCtrl/2022 Decomm WP/Revised Decomm WP/01_text/202207_Tracy_Wood_Decomm WP_text.docx