The Longest Tunnel in Oregon Includes a Time Travel Adventure

The longest tunnel in Oregon is technically two tunnels, or bores, that run side by side through the Tualatin mountains, extending light rail service from downtown Portland westward to the cities of Beaverton and Hillsboro. The Robertson Tunnel is used by the Red Line and Blue Line of the Portland area metro system, Metropolitan Area Express (MAX). There’s a single station inside the tunnel.

When Was Oregon’s Longest Tunnel Built?

After at least five years of planning, the construction began in 1993 on the west side of the route, with work on the east side beginning in 1994. The west side excavation used explosives to tunnel into the mountainside. On the east side, drillers used a boring machine.

That is, not a machine that’s uninteresting, but a Gigundo drilling machine that bores through solid rock! Which seems great, except the rock beneath the mountain was looser than anticipated. So the construction firm put drilling on hold for nine months while engineers searched for a way to deal with crumbling rock that blocked the machine’s progress. The solution was to shoot a special cement ahead of the boring machine, so the rock ahead would hold its shape.

Other complicating factors included noise from the blasting (special rubber curtains had to be installed to dampen the explosions), a lawsuit to prevent the tunnel from passing beneath a cemetery (the project was granted an easement to keep to the planned route), and a congressional staffer who slipped in a puddle of muck during a tunnel inspection (reimbursement for her ruined suit triggered an ethics investigation). Nevertheless, the east and west side tunneling projects met in December of 1995. The tunnel was placed into service in September 1998.

How Long is Oregon’s Longest Tunnel?

The tunnel is 2.9 miles long, and each bore is 21 feet in diameter. Trains pass the length of the tunnel in 5 minutes, including a stop at Washington Station, the only station in the tunnel. During that time, passengers pass through basalt rock that’s up to 16 million years old.

Washington Station Is One of The Deepest Train Stations on Earth

Besides being the longest transportation tunnel in Oregon, the Roberston Tunnel also holds the deepest transit station in the western hemisphere and the seventh-deepest in the world. Washington Station is 260 feet below ground; two high-speed elevators bring travelers to and from the surface. The elevator ride takes about 25 seconds to travel the equivalent distance of a 26-story building. And in a temporal sense, traveling from the tunnel’s ancient rock to the surface is an even greater journey. So the two elevator stops, surface, and tunnel, are labeled “The Present” and “16 million years ago.”

Where is The Robertson Tunnel Located on a Map?

The Robertson Tunnel is a dual-bore light rail tunnel situated in the Tualatin Mountains to the west of Portland, Oregon, United States. It serves as a passage for the MAX Blue and Red Lines. Spanning a length of 2.9 miles, the tunnel comprises two tunnels with a diameter of 21 feet each.

Here is The Robertson Tunnel on a map:

The photo featured at the top of this post is © Box Lab/Shutterstock.com