In June 2017, SpaceX and Tesla CEO Elon Musk took to Twitter to make what seemed like a huge announcement. His less-than-a-year-old Boring Company—a venture dedicated to vanquishing traffic by quickly building futuristic underground high-speed mass transit systems—had received “verbal government approval” for “an underground NY-Phil-Balt-DC Hyperloop,” he wrote. The hyperloop, he promised, would one day transport travelers between New York and the nation’s capital in just under 30 minutes.

But when it comes to large-scale infrastructure projects, “verbal government approval” and “government approval” are very different things. Now Musk and the Boring Company are working through the boring part: the long and paperwork-intensive process of building a scaled-down version of their vision, called the Loop. On Thursday, almost two years after Musk’s tweet, the company took a small but necessary step toward making the Loop a reality: It published a sprawling, 505-page draft environmental assessment. The report, published in conjunction with an alphabet soup of federal, state, and regional agencies, is required under environmental laws.

The report lays out, often in meticulous detail, what Musk and his company plan for their East Coast mass transit system. If completed, the privately funded Loop would carry passengers between downtown Baltimore and Washington through twin 35-mile tunnels 30 to 90 feet below the surface. Battery-powered “autonomous electric vehicles,” or AEVs, would shoot passengers at speeds up to 150 mph, completing the trip in approximately 15 minutes. Seventy ventilation shafts, housed in nondescript brown huts built on the surface of the route, would help passengers breathe—and serve as emergency exits. Fares would be “comparable to public transportation,” the company writes.

At some point, the company wrote in its assessment, the Baltimore-Washington segment could link to a more sprawling one, carrying riders to New York at speeds up to 700 mph—nearly the speed of sound—in a vacuum-tubed hyperloop. When? That’s anyone’s guess: “The

potential future use of hyperloop technology is currently unknown,” the company writes. For the immediate future, the system could only carry a maximum 2,000 passengers each day—fewer than two full New York City subway trains.

The company says the project is needed because the wider DC region is plagued by terrible traffic. But the company notes that the Loop would face competition from many other transportation options: highways, including I-95; intercity buses; trains from Maryland Rail Commuter Services, or MARC, which transports riders between DC and Baltimore in just over an hour; and Amtrak. (The nationalized rail service is in the midst of a $2.45-billion revamp of its popular Northeast Corridor Acela service, which would shorten the now 35-minute trip and allow Amtrak to run more frequent service between Boston and DC.)

In the draft assessment, The Boring Company promises a speedy construction process. It says eight to 16 tunnel boring machines could get the whole thing done in 15 to 23 months, depending on the company’s ability to improve its tunnel boring tech. (Compare that to the eight years it took New York to build a less-than-two-mile subway extension.)

LEARN MORE The WIRED Guide to Hyperloop

Before it can stick a tunnel-boring machine in the ground, however, the project will need to run a gauntlet of government approvals, including from the Maryland Department of Transportation, the District of Columbia Department of Transportation, the federal Department of Transportation, the city of Baltimore, the National Park Service, the Army Corps of Engineers, and potentially Maryland legislators. It would need to pass muster with regional water and environmental authorities. (The assessment includes a lengthy interlude on the project’s effects on local dragonfly species.) It might need a set of purpose-built regulations for its new tech, approved for the Federal Railroad Administration. And it would be subject to a handful of public comment periods—the first of which began Thursday with the posting of the draft assessment. (Go ahead! Submit your public comments here!)