The U.S. Navy is preparing plans to construct sprawling detention centers for tens of thousands of immigrants on remote bases in California, Alabama and Arizona, escalating the military’s task in implementing President Donald Trump’s “zero tolerance” policy for people caught crossing the Southern border, according to a copy of a draft memo obtained by TIME.

The internal document, drafted for the Navy Secretary’s approval, signals how the military is anticipating its role in Trump’s immigration crackdown. The planning document indicates a potential growing military responsibility in an administration caught flat-footed in having to house waves of migrants awaiting civilian criminal proceedings.

The Navy memo outlines plans to build “temporary and austere” tent cities to house 25,000 migrants at abandoned airfields just outside the Florida panhandle near Mobile, Alabama, at Navy Outlying Field Wolf in Orange Beach, Alabama, and nearby Navy Outlying Field Silverhill.

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