Seattle’s other tunneling machines are officially finished drilling the last of twin 3.5 mile long tunnels between the University of Washington light rail station and a location less than one mile from a future Northgate station.

Sound Transit, the region’s public transit agency, said these are the last tunnels to use tunnel boring machines on current agency projects. The excavation is complete three months ahead of schedule according to the agency. A separate tunnel project in Bellevue will use other tunneling techniques.

From here, the extension to Northgate goes above ground on an elevated track way. The extension to Northgate is due to open in 2021, and the further extension to Lynnwood in 2023. Construction of above ground structures is faster than tunneling according to the agency.

As construction of those projects and light rail to the east side continues, voters will be asked to consider dramatically enlarging the system. The proposal would add another 62 miles of light rail to Everett on the north side, and Tacoma on the south, with further extensions on the east side of Lake Washington.

Called ST3, the $54 billion price tag would build projects out to 2041, and included dedicated busways on Interstate 405 with extended and more frequent Sounder commuter trains and stations south of Seattle and Tacoma.

There are no plans to enlarge Sounder service north of Seattle under ST3.

ST3 would raise motor vehicle and property taxes, and the proposal is already seeing some opposition. The vote is scheduled for November 8.

ST3 would include additional tunneling for more capacity under downtown Seattle, and according to South Transit bring the region much closer to other major cities with extensive public transit networks.

As for the tunneling machines, referred to as number 1 and 2, they are much smaller than Bertha, one of the world’s biggest tunneling machines.

Bertha is mining a nearly 60-foot wide highway tunnel under downtown Seattle. It is currently paused for a maintenance stop to allow change out of cutting tools and is expected to hit the half way mark in the near future according to the Washington State Department of Transportation.