Additional Remediation Goal for Arsenic Installation Restoration Site 12 Former Naval Station Treasure Island San Francisco, California October 2024 The Department of Navy (DON) has prepared an Explanation of Significant Differences (ESD) for the Record of Decision/Final Remedial Action Plan (ROD/Final RAP) (DON, 2017) for Installation Restoration (IR) Site 12 at Former Naval Station Treasure Island (NSTI). The purpose of this ESD is to establish a groundwater remedial goal (RG) for arsenic. The ESD has been prepared in accordance with a Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other Remedy Selection Documents (United States Environmental Protection Agency, 1999) pursuant to Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) section 117(c) and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) 40 Code of Federal Regulations (CFR), section 300.435(c)(2)(i). The document can be reviewed in its entirety by first visiting the BRAC Former Treasure Island Documents website: https://www.bracpmo.navy.mil/BRAC-Bases/California/Former-Naval-Station-Treasure-Island/Documents, selecting Administrative Records, then entering Final Explanation of Significant Differences, Site 12 in the search administrative records box. QUESTIONS? David Clark David.j.clark9.civ@us.navy.mil