Toothrock Tunnel on Columbia River Highway – Bonneville OR


The US Bureau of Public Roads (BPR) built the Toothrock Tunnel No. 4555  on the Columbia Gorge Highway near Bonneville, Oregon.

Heading east on Interstate-84, as one approaches the Bonneville Dam, vehicles pass through an 837-foot, semicircular bore into Tooth Rock. Today, Toothrock Tunnel’s artful design of basalt rockwork and concrete construction can be appreciated for its rustic, historic appearance as well as its ‘natural’ fit with the mountainous characteristics of the area.

When plans were unveiled for it in 1935, however, it represented major improvements in modern highway design with its “skewed arch portals” fitting topographic conditions and a state-or-the-art lighting system for day-time driving conditions, which the tunnel’s length and curvature required. The BPR district engineer for the project claimed at the time of its completion that it was the first rural tunnel in North America with such illumination. The Oregonian informed the newspaper’s readers that “general illumination of important highways is no longer a distant probability but the next major improvement in modern highway design.” The District Engineer further noted that the illumination would be powered by the newly constructed Bonneville Dam.

Construction of the Bonneville Dam in 1934 set in motion the need for a number of changes to transportation through the Columbia Gorge on the Oregon side of the river. Pooling from the dam would cover the Union Pacific Railroad’s mainline so required moving the tracks. That rerouting in turn disrupted the original alignment of the Columbia River Highway. Despite the fact the Columbia River Highway was less than twenty years old, planners already saw an opportunity to reduce the costs of transportation given the state highway’s significant grade changes by seeking federal funds to construct a new “water-level route” along the southside of the Columbia River, and the section between Cascade Locks and the Bonneville Dam was the first section to be finished.

While BPR engineers designed construction plans for the tunnel’s 26-foot roadway and 4-foot sidewalks, National Park Service designers drew detailed plans for the portals and entry wall rockwork. Although difficult to verify, those preparing the Oregon Inventory of Historic Properties documentation speculate that the actual stonework for the tunnel was completed by a Work Progress Administration (WPA) crew lead by master mason Ralph Curcio. Curcio, an Italian immigrant know for his work on the historic Columbia River Highway, lead a WPA crew on other tunnels constructed soon after Toothrock, including the Rocky Butte Tunnel and West Burnside Tunnel.

In 1969, the Eagle Creek Viaduct was completed to carry west-bound interstate traffic around Tooth Rock, thus reducing Toothrock Tunnel to east-bound travel lanes for Interstate-84. Toothrock Tunnel is also referred to as the Bonneville Tunnel.

Source notes

Hadlow, Robert (2002) Department of Transportation submission: Oregon Inventory of Historic Properties - Section 106 Documentation Form. Recorded: 2 September 2002.

Oregonian (1935) "Bonneville Highway Plans Await Federal Sanction," May 5, 1935, p. 59.

Oregonian (1935) "Tooth Rock Bore Design Approved," September 18, 1935, p. 16.

Oregonian (1935) "Engineer Studies Vapor Lighting: New Idea Considered for Toothrock Tunnel," October 8, 1935, p. 12.

Oregonian (1937) "Tooth Rock Tunnel on Relocated Columbia River Highway, Completed," August 15, 1937.

Project originally submitted by Judith Kenny on June 26, 2019.

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Location Info

Toothrock Tunnel
Bonneville, OR 97014

Location notes: Interstate 84 near Bonneville Dam.

Coordinates: 45.6311, -121.957

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