US Citizenship and Immigration Services (USCIS) expects to spend an estimated $38.3bn on a plan to acquire warehouses across the country and retrofit them into new immigration detention centers with capacity for tens of thousands of detainees, according to documents the agency sent to the governor of New Hampshire.

The documents, published on the state’s website on Thursday, disclose that the Department of Homeland Security (DHS) estimates it will spend $158m retrofitting a new detention facility in Merrimack, New Hampshire, and an additional estimated $146m to operate the facility in the first three years.

According to an overview of the plans, which were first reported by the Washington Post, Immigration and Customs Enforcement (ICE) would buy and convert 16 buildings across the US into regional processing centers, each holding between 1,000 and 1,500 people at a time. Another eight large-scale detention centers would hold 7,000 to 10,000 people at a time and serve as “the primary locations” for deportations. Detainees would spend an average of three to seven days at the processing sites before being transported to the larger facilities, where they would be held about 60 days before being deported.

The new model for increasing detention space is needed, according to the document, due to a surge in ICE hires and an anticipated rise in arrests. The number of people in ICE detention has it records in the second Trump administration.

These facilities will “ensure the safe and humane civil detention of aliens in ICE custody, while helping ICE effectuate mass deportations”, the documents said. The effort will rely on the billions of dollars appropriated by Congress in the One Big Beautiful Bill Act to “fully implement a new detention model by the end of Fiscal Year 2026”, according to the documents.

Together, the records provide the clearest view so far of the Trump administration’s strategy to reshape immigrant detention by converting buildings initially built for industrial use – a broad undertaking intended to strengthen ICE’s capacity to apprehend more immigrants and remove them more quickly.

Instead of transferring detainees around the country based on open bed space, the redesigned system would channel individuals into a network of large centralized facilities where they would remain until deportation, according to ICE’s planning documents.

There appear to be conflicting statements about when the economic impact analysis for the proposed Merrimack facility was delivered to New Hampshire’s governor, Kelly Ayotte.

Ayotte, a Republican, said in a press release that DHS provided the documents to her office for the first time on Thursday. Her remarks seemed to conflict with testimony from Todd M Lyons, ICE’s acting director, who told a Senate hearing earlier that same day that DHS representatives had already discussed the project with the governor and supplied “an economic impact summary” to her.

Massachusetts governor Maura Healey issued a statement opposing the creation of an ICE agency detention center in Merrimack, calling it “outrageous and absolutely the wrong move”.

“ICE is shooting people dead on the street. Mothers have been ripped from cars and separated from children,” the statement said. “US Citizens have been stopped, detained and even killed. Peaceful protestors have been assaulted. Parents are afraid to send kids to school, to go to church, to seek healthcare and report crimes. None of this makes people safer – it makes us all less safe.”

It continued: “We should be opposing ICE’s tactics, not allowing them to expand. We certainly should not be allowing ICE to build new human warehouses when they can’t be trusted to keep people safe and protect due process.”