The Air Force is reopening the environmental review for Sentinel, the ICBM replacing Minuteman III, because its plan to build Sentinel silos inside the old launch facilities didn’t survive contact with cost and schedule. A notice of intent published Oct. 9 in the Federal Register starts a supplemental environmental impact statement covering new launch silo sites, launch centers, land purchases and fresh utility corridors in missile fields across five states.
That’s a big change in what gets built. The 2023 EIS and its May 2023 record of decision assumed the Department of the Air Force would recapitalize existing Minuteman III infrastructure at F.E. Warren Air Force Base in Wyoming, Malmstrom in Montana and Minot in North Dakota. The new notice says that approach “could not be carried forward.” Converting existing launch facilities into launch silos carried cost and schedule risks that put key milestones out of reach, and a July 2024 acquisition decision memorandum ordered the program restructured.
What the New Sentinel Silo Plan Adds
The proposed action reads like a scope sheet for a heavy civil program. It allows up to 30 new launch silo sites at F.E. Warren and up to 60 new sites at Malmstrom and Minot. Qualifying launch facilities would still be converted where they work. A selected number of existing Minuteman sites would be closed in place, and old missile alert facilities would be reused to develop launch centers.
New ground comes with it. The notice calls for real estate acquisitions for new silo and launch center sites at F.E. Warren and Minot, with the Warren field expanding northwest and Minot’s spreading west and east. Malmstrom would reuse sites from the former 564th Missile Squadron as swing space and add temporary laydown areas. The list also includes MH-139 helicopter refueling and rearming at selected launch centers, more on-base facilities, and workforce hubs redesigned and relocated “to support construction efficiency.”
Sentinel’s Utility Corridors Get Rebuilt, Too
The cabling may be the sleeper item. Under the 2023 plan, which the notice keeps as its no-action baseline, the Air Force would have reused 80% of existing utility corridors and built only 20% new. The supplemental review covers easements for new corridors, including fiber-optic lines the 2023 EIS never evaluated. The service says the no-action alternative isn’t reasonable anymore because cost, schedule, siting and engineering constraints make it unachievable. Some work may also land in floodplains.
The Army Corps of Engineers, the Bureau of Land Management and five other federal agencies will be invited to join as cooperating agencies. Tetra Tech is handling the scoping comment inbox.
The Schedule Behind the Sentinel Silos
Scoping runs 30 days from publication, which puts the soft deadline around Nov. 8. The draft supplemental EIS is due for public comment in fall 2027 and the final in spring 2028. That’s the environmental paper trail for silo sites on land the government doesn’t own yet.
Construction isn’t waiting for all of it. Northrop Grumman, the Sentinel prime, and Bechtel broke ground in March on a prototype silo near Promontory, Utah, meant to prove out a repeatable, modular build method, Stars and Stripes reported. The Air Force has said it wants a flight test in 2027 and operational missiles in the early 2030s.
The money is the open question. The program’s estimate jumped 81% to about $141 billion in the 2024 Nunn-McCurdy review, and officials said in February that a cost estimate for the restructured plan wouldn’t arrive until the end of 2026. Defense infrastructure has a habit of outgrowing its first number. GAO now sizes the Navy’s shipyard program above $200 billion, up from a $21 billion plan, as Exchange reported last month. Contractors chasing the work should read it the way they read the $9 billion NAVFAC Northwest MACC: task orders tell you what’s real, ceilings don’t.
For now, the Air Force’s own timeline puts the final environmental word on new silo ground in spring 2028. The missiles are due a couple of years later.