The Department of the Air Force (DAF) has formally initiated the preparation of a Supplemental Environmental Impact Statement (SEIS) concerning the deployment of the Sentinel intercontinental ballistic missile (ICBM) system and the decommissioning and disposal of the current Minuteman III (MMIII) ICBMs. This significant development, outlined in a Federal Register notice published on October 9, 2026, signals a critical juncture in the modernization of the land-based component of the nation's nuclear deterrent. The SEIS is necessary to analyze the environmental implications of substantial changes to the Proposed Action originally detailed in the 2023 Environmental Impact Statement (EIS) and the subsequent May 2023 Record of Decision (ROD).
Background of the Sentinel Program
The Sentinel Program, previously known as the Ground Based Strategic Deterrent (GBSD), represents the DAF's effort to replace the aging Minuteman III fleet, which has been operational for decades. The 2023 EIS and May 2023 ROD had laid out a plan for the sequential replacement of all land-based MMIII missiles in the United States with the technologically advanced Sentinel system. This original strategy largely envisioned the reutilization of existing infrastructure at Francis E. Warren Air Force Base (FE Warren) in Wyoming, Malmstrom Air Force Base (Malmstrom) in Montana, and Minot Air Force Base (Minot) in North Dakota, as well as their associated missile fields across five states. The overarching purpose remains to maintain a safe, secure, and effective ICBM capability to support national security objectives.
Rationale for the Supplemental Environmental Impact Statement
The decision to prepare an SEIS stems from a critical reassessment of the original deployment strategy. The DAF determined that the initial approach of recapitalizing all existing MMIII infrastructure was no longer viable due to significant cost and schedule risks. Specifically, the conversion of existing Launch Facility (LF) sites to the more modern Launch Silo (LS) sites presented unforeseen challenges that rendered key Sentinel Program milestones unachievable. This led to a July 2024 Acquisition Decision Memorandum directing a restructuring of the Sentinel Program. The DAF subsequently evaluated optimized deployment strategies aimed at reducing execution risk, stabilizing costs, and addressing the complexities associated with legacy infrastructure. The new strategy pivots from heavy reliance on legacy facility reutilization to the construction of modernized, new-built LS sites designed for adaptability to future technological advancements.
The SEIS is being prepared in accordance with the National Environmental Policy Act of 1969 (NEPA), as amended by the Fiscal Responsibility Act of 2023, along with the 2026 Department of War and the 2026 DAF NEPA Implementing Procedures. The DAF serves as the lead agency for this undertaking.
Key Components of the Revised Proposed Action
The revised Proposed Action analyzed in the SEIS includes several significant changes to the original plan. At each missile field, the DAF proposes redesigns, functional changes, and potential relocation of workforce hubs to enhance construction efficiency. A notable aspect is the closure in place of a selected number of the current 150 MMIII LF sites, coupled with the disposal of existing Missile Alert Facility (MAF) and LF sites. While some qualifying LF sites may still be converted to LS sites, the primary shift is towards new construction. MAF sites may be reutilized for Launch Center (LC) development. The plan also includes the procurement of easements for new utility corridors, specifically fiber-optic cables, an element not extensively evaluated in the 2023 EIS. Furthermore, in-field MH-139 Grey Wolf helicopter refueling and rearming capabilities will be established at selected LC sites, and additional on-base facilities and infrastructure will be constructed.
Specific to individual bases, the Proposed Action includes land acquisition through real estate transactions for new LS and LC sites at FE Warren and Minot. FE Warren may see the possible replacement of an existing LF site with an LC site and an expansion northwest of its existing missile field. Minot's missile field is slated for expansion both west and east. At Malmstrom, former 564th Missile Squadron geographic sites will be reutilized as swing space, and temporary laydown areas will be established. The plan envisions up to 30 new LS sites at FE Warren and up to 60 new LS sites at both Malmstrom and Minot.
The No Action Alternative and Floodplain Considerations
The SEIS will also consider a No Action Alternative, which would entail continuing to implement the May 2023 ROD. Under this alternative, the DAF would proceed with the sequential replacement of all land-based MMIII ICBMs, reutilizing 80 percent of existing utility corridors while constructing only 20 percent of new utility corridors in newly established easements. However, the DAF has determined that the No Action Alternative is not a reasonable or achievable path forward due to insurmountable cost, schedule, siting, and engineering constraints. Despite its unfeasibility, this alternative provides a baseline for comparing the environmental impacts of the revised Proposed Action.
Separately, the DAF has identified that portions of the Proposed Action have the potential to be located within a floodplain. Consequently, the project is subject to the requirements and objectives of Executive Order 11988, "Floodplain Management," issued by President Trump. This Notice of Intent also serves as the public notice mandated by E.O. 11988 to foster early and meaningful public participation in addressing potential floodplain impacts.
Public Engagement and Timeline
To ensure transparency and public involvement, the DAF has initiated a 30-day public scoping period, beginning with the publication of the Notice of Intent. During this period, the DAF actively solicits comments on alternatives, potential impacts, relevant information, studies, or analyses pertaining to the Proposed Action. While comments are accepted throughout the SEIS process, submission within this initial 30-day window is encouraged for maximum consideration. The Draft SEIS is anticipated for release for public comment in fall 2027, with the Final SEIS projected for publication in spring 2028. Several federal agencies, including the Bureau of Indian Affairs, Bureau of Land Management, U.S. Army Corps of Engineers, and U.S. Fish and Wildlife Service, will be invited to participate as Cooperating Agencies. The DAF will also consult with federally recognized Native American Tribes and other federal agencies with relevant jurisdiction or expertise.
