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Rationale for Considering Conditional - 2 - 25 March 2026 No Further Action Olin Chlor Alkali Facility Tracy, San Joaquin County, California of the Site. The surrounding area is primarily agricultural lands with some mixed-use light industrial and low-density residential areas along South Banta Road. Between 1975 and 1989, All-Pure Chemical Company (All Pure) operated the Site as a bleach manufacturing and distribution facility. In 1989, Pioneer Americas Inc. (Pioneer) acquired the All Pure business and began leasing the Site. In 2007, Olin Chlor acquired Pioneer and the property lease and continued liquid bleach production and chlorine gas repackaging. In 2009, chlorine gas repackaging operations ceased, and during the second quarter of 2022, liquid bleach production ceased. The original All Pure owner remains the current property owner and the Site is vacant. The Defense Logistics Agency, Tracy Site (DLA-Tracy) is a 910-acre United States Environmental Protection Agency (USEPA) Superfund site located 1,500 feet northwest of the Site. DLA-Tracy is hydraulically cross-gradient to the Site and known to be impacted by trichloroethene contamination. Geology: The Site is in the northwest part of the San Joaquin Valley and overlies recent Quaternary deposits and the Tulare Formation. The Upper Tulare Member reaches thicknesses of 200 feet near the Site. The Middle Tulare Member is the Corcoran Clay aquitard, estimated to be 220 to 250 feet thick, and the Lower Tulare Member, like the Upper, consists of permeable material. The upper 100 feet of Iithology has been described as primarily silty clays containing layers of fine-to-medium sand and silt. Hydrogeology: The Site groundwater monitoring wells are installed in the upper 100 feet of Iithology and have been divided into Site-specific groundwater zones (upper, middle, and lower). During the March 2025 groundwater monitoring event, the depth to groundwater measured approximately 20 to 25 feet below ground surface (bgs) and groundwater has consistently flowed to the northeast since Site investigations began (Figures 3 and 4). Local to the Site, large-scale agricultural, municipal, and industrial groundwater extraction is from below the Corcoran Clay. Groundwater above the Corcoran Clay is often of poor quality based on elevated chloride, nitrate, and boron. Source: The COC source is interpreted to be from releases between 1975 to 1989 to two former ponds (Ponds 1 and 2) during liquid bleach production, storage and distribution of calcium hypochlorite, repackaging of chlorine gas and sulfuric acid, and on-Site truck maintenance. Remedial Investigations and Actions: Remedial actions have primarily included monitored natural attenuation (MNA) and active remediation by soil excavation. The constituents of concern (COCs) remaining in groundwater at the Site include carbon tetrachloride (CC14) and chloroform (CF).