One of two tunneling machines digging a light-rail route between the University of Washington and Capitol Hill surfaced Wednesday morning, finishing a nearly two-mile journey and marking a significant milestone in the multi-year project.

The 21-foot diameter machine, named Togo, wormed through a final layer of soil and grout around 4 a.m. to reach the large concrete pit that will someday be a light-rail station at Broadway and John Street.

Its trip began last spring from a future station outside Husky Stadium on the University of Washington campus.

A second machine, Balto, is about a month behind Togo in its subterranean journey to Capitol Hill. Tunnel contractors named the machines after famous Husky sled dogs that relayed to deliver medicine 674 miles from Anchorage to Nome, Alaska, during a diphtheria outbreak in 1925, according to Sound Transit.

Each machine is about as long as a football field and weighs at least 679,000 pounds. The massive cutting heads mine about 44 to 50 feet of earth per day. Massive prefabricated concrete rings with rubberized gaskets are left in place to form the tunnels.

During its nearly 10-month journey, the machine tunneled under the Montlake Cut, state Route 520 and the Volunteer Park water tower.

Altogether, three machines are digging the $1.9 billion, 3.1-mile U-Link extension of the light-rail system from Westlake Center to the station at Cal Anderson Park and the UW campus.

A third machine, Brenda, is digging the second of two one-mile tunnels between Capitol Hill and Westlake.

Expanded light-rail service is expected to start in 2016, adding an estimated 70,000 daily riders to the system. Tunneling between Capitol Hill and downtown, which started last May, is expected to last more than a year. Sound Transit plans to extend trains to Northgate and Lynnwood by 2023.