Arlington Heights in Portland in Multnomah County, Oregon — The American West (Northwest)

Robertson Tunnel

Photographed by Ian Lefkowitz, June 26, 2026

1. Robertson Tunnel Marker

Inscription. The volcanic rock beneath the city that makes up most of the ground beneath your feet is basalt. In Portland’s West Hills it erupted as lava flows, but also formed in deep basalts as far away as where Pendleton is today, that flowed all the way to the Pacific Ocean.

This 21-foot-3-inch-diameter circle represents the cross-section of one of the twin three-mile tunnels below.

The tunnels were excavated between 1994 and 1996.

From the east, a tunneling machine drilled two miles.

From the west, miners used explosives to excavate one mile.

The rock fa... “kissed by the cutter”…

Tunneling took 481,216 person-hours — up to 32 miners per shift, around the clock, six days a week, for over two years.

It took 126,000 cubic yards of concrete to line the two tunnels.

The average miner was 37 years old; he earned about 21 dollars an hour.

Geologists drilled 102 test holes and collected 20,000 feet of core samples.

Crew size at any one time averaged 16 workers.

Temperature in the tunnels averages 53 degrees Fahrenheit year-round.

The tunnel boring machine wore out 341 cutter discs, each weighing about 400 pounds.

peak water flow...construction of

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the tunnels...was 2,000 gallons per minute.

The miners consumed 54,962 cups of coffee.

The volcanic rock through which the tunnels pass is 15.6 million years old.

Excavated materials...Swelled as much as 50 percent...when removed…

During the excavation of the tunnels, 420,405 cubic yards of rock were removed — enough to fill a 19-story building the size of a football field.

The miners wore out 1,481 pairs of rubber boots.

Topics. This historical marker is listed in these topic lists: Bridges & Viaducts • Man-Made Features • Railroads & Streetcars. A significant historical year for this entry is 1996.

Location. 45° 30.632′ N, 122° 43.012′ W. Marker is in Portland, Oregon, in Multnomah County. It is in Arlington Heights. It can be reached from the intersection of Southwest Canyon Road and Southwest Zoo Road, on the left when traveling north. Touch for map. Marker is at or near this postal address: 4027 SW Canyon Road, Portland OR 97221, United States of America. Touch for directions.

Regionally, this marker is in Oregon’s Columbia River Gorge

and in the Willamette Valley.

It is also on the American Pacific Coast,

in the

Photographed by Ian Lefkowitz, June 26, 2026

2. Robertson Tunnel Marker

The marker contains tunneling facts and history, cut on each side to fit within a sample of tunnel core that has been embedded into the ground.

Pacific Northwest,

and in the Lewis & Clark Corridor.

Globally, it is in North America,

on the Ring of Fire,

in the Pacific Rim,

in the Western Hemisphere,

in the Western World,

and in the Anglosphere.

Other nearby markers. At least 8 other markers are within 2 miles of this marker, measured as the crow flies: MIA (approx. 0.2 miles away); "For You A Rose in Portland Grows" (approx. ¾ mile away); The Willamette Stone (approx. 1.4 miles away); a different marker also named The Willamette Stone (approx. 1½ miles away); Simon Benson (approx. 1½ miles away); Oklahoma City Bombing Memorial (approx. 1.6 miles away); Peace Plaza (approx. 1.7 miles away); The Great Plank Road (approx. 1.7 miles away). Touch for a list and map of all markers in Portland.

Also see . . . The Inside Story of the Robertson Tunnel (Tri-Met).

This tunnel through the West Hills – allowing MAX to extend from Portland to Beaverton and Hillsboro — is nearly three miles long and drilled through challenging and often unstable earth. At 259 feet deep, Washington Park MAX station in the tunnel is the deepest transit station in North America (and the
Photographed by Ian Lefkowitz, June 26, 2026

3. Washington Park Elevator
The elevator leading to the station platform indicates the scale of the project, the deepest subway station in America.
fifth deepest in the world).

(Submitted on August 31, 2026, by Ian Lefkowitz of New York, New York.)

Robertson Tunnel Core Sample image. Click for full size.

Photographed by Ian Lefkowitz, June 26, 2026

4. Robertson Tunnel Core Sample

The core sample can be found at platform level, within the Robertson Tunnel itself.

Credits. This page was last revised on September 1, 2026. It was originally submitted on August 31, 2026, by Ian Lefkowitz of New York, New York. This page has been viewed 9 times since then. Photos: 1, 2, 3, 4. submitted on August 31, 2026, by Ian Lefkowitz of New York, New York. • Andrew Ruppenstein was the editor who published this page.