Permission to excavate in the city could be a first step to building an East Coast Hyperloop—or just an expensive folly.

Backstory: Last July, Musk announced “verbal government approval” for an underground Hyperloop between New York City and Washington, DC. Some folks scoffed, arguing that metropolitan planning doesn’t really work via verbal agreements.

What’s new:  The Washington Post reports that his tunneling startup, the Boring Company, has now received an “early, and vague, building permit” from Washington, DC. The permit allows it to do some excavation experimentation in a parking lot in the NoMa area of the city. (Similar tests are under way beneath SpaceX HQ in California.)

But: There are no details about how far or deep a tunnel might stretch, or for how long experimentation can last. And while Musk insists such tunnels are the solution to congested streets, transport experts aren’t convinced. He may get a tunnel in DC, but an East Coast Hyperloop is quite another thing.