Historic Mitchell Point Tunnel Makeover Complete: Ready for Big Reveal

The public recently enjoyed its first look at the WSP-designed Mitchell Point Tunnel, a reconstructed pedestrian and bicycle passageway along the Historic Columbia River Highway State Trail that is preparing to reopen 70 years after permanently closing to vehicle traffic.

A Nov. 16 dedication event was attended by more than 500 people, providing visitors with an opportunity to experience the rebuilt 655-foot-long tunnel carved into a basalt rock mountain before it officially opens to walkers, joggers and bike riders in early 2025.

The $31 million project, funded through the Federal Lands Access Program, and delivered by the Western Federal Lands Highway Division of the Federal Highway Administration (FHWA), is owned by the Oregon Department of Transportation (ODOT) and operated by Oregon Parks and Recreation Department (OPRD).

“Many places across the U.S. are repurposing historic and abandoned rail alignments into public trails,” said John Horne, senior vice president at WSP and the Mitchell Point Tunnel project manager. “In this case, we created a trail along the original highway route that was used before the lower roadway was constructed. It is a remarkable project.”

Since 2015, WSP has led all design-related aspects of the Mitchell Point Tunnel, including project feasibility, alternatives analysis, route selection, detailed engineering, contract documents and bid/construction support. Crestline Construction served as general contractor, and the tunnel was mined by LRL Construction. Schuepbach Custom Builders was responsible for concrete, while Guinette Masonry placed the spectacular basalt stonework on the portals and approach railing.

Located in the Columbia River Gorge National Scenic Area, the tunnel is the centerpiece of a new 1.5-mile segment of the Historic Columbia River Highway State Trail, which will connect recreational corridors to the east and west.

When fully connected, the trail will provide a safe and scenic 73-mile route that follows the Historic Columbia River Highway between Portland and The Dalles. The Historic Columbia River Highway is listed on the National Register of Historic Places, is designated as a National Historic Landmark by the U.S. Secretary of the Interior and is being designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.

The new tunnel traverses the side of a mountain about 100 feet above the current highway route, with five scenic openings cut into the mountain, providing users with spectacular views of the Columbia River as it follows the route motorists traveled regularly more than a century ago.

Constructing a tunnel in a federally protected area required careful plan design and approval to guarantee minimal disturbance to the mountainside and its natural surroundings, down to specifying the proper colors and textures for all exposed materials. Portal and adit (horizontal passageway for ventilation) locations were adjusted to minimize disturbance of endemic plant species like the Douglasia laevigata — also known as the cliff dwarf primrose. Vibration and noise monitoring during tunnel blasting was required to protect peregrine falcon nesting habitat.

Click on the arrows for a tour of Mitchell Point Tunnel and images from the Nov. 16 dedication event.

Retaining Its Natural Character

Illumination of the tunnel was also a key consideration, as stakeholders determined whether artificial lighting would be needed or if natural lighting would be sufficient to provide safe passage. A WSP-led analysis of illumination options allowed the agencies to conclude that the five scenic view “piercings” along the tunnel would provide sufficient natural lighting throughout the entire passageway and supplemental LED lights would not be necessary, further preserving the tunnel’s natural integrity.

The original 390-foot-long tunnel was designed by John Arthur Elliott, engineer for the Columbia River Highway construction project, and was opened to vehicle traffic in 1915. Elliot drew inspiration from Switzerland’s famed Axenstrausse roadway above Lake Lucerne and incorporated five viewing windows in his design. The original tunnel was closed in 1953 when the agency constructed US 30, a water-level route around Mitchell Point. It was subsequently destroyed in 1966 to make room for Interstate 84.

Horne said it has been an honor to have the opportunity to revive Elliot’s original creation.

“When I look at the historic tunnel today and reflect on what Elliot accomplished in his time —and then think that I had the privilege to serve as chief engineer to restore his tunnel — that’s a satisfying accomplishment,” Horne said. “Mitchell Point Tunnel is not only a signature project for WSP, but for me personally, it’s been a pinnacle of my engineering career.”