page_title: Historic Columbia River Highway
section_title: Water-level bypass
hierarchical_section_title: Historic Columbia River Highway / History / Water-level bypass
caption_attribution_description: EAGLE CREEK BRIDGE, VIEW OF NORTH END LOOKING 222 DEGREES SOUTHWEST. SCENIC VIEW AREA VISIBLE AT REAR OF RIGHT SIDE OF BRIDGE.
context_page_description: The Historic Columbia River Highway is an approximately 75-mile-long scenic highway in the U.S. state of Oregon between Troutdale and The Dalles, built through the Columbia River Gorge between 1913 and 1922. As the first planned scenic roadway in the United States, it has been recognized in numerous ways, including a listing on the National Register of Historic Places as a National Historic Landmark, designation as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers, and considered a "destination unto itself" as an All-American Road by the U.S. Secretary of Transportation. The historic roadway was bypassed by the present Columbia River Highway No. 2 from the 1930s to the 1950s, leaving behind the old two-lane road. The road is now mostly owned and maintained by the state through the Oregon Department of Transportation as the Historic Columbia River Highway No. 100 or the Oregon Parks and Recreation Department as the Historic Columbia River Highway State Trail.
  The original highway was promoted by lawyer and entrepreneur Sam Hill and engineer Samuel C. Lancaster, to be modeled after the great scenic roads of Europe.
context_section_description: Even as construction was ongoing on the east end of the Columbia River Highway, the design had become obsolete, as motorists wanting to get to their destination greatly outnumbered tourists taking a pleasure drive. There were also problems with rockfall, especially west of the Mosier Twin Tunnels. By 1932, Lancaster proposed a new water-level route, while keeping the old road as a scenic highway. The first such bypass was necessitated by the federal government's creation of Bonneville Dam on the Columbia River. The dam would flood the railroad, and the highway would need to be moved so the railroad could take its place. The highway's new two-lane alignment, completed in 1937, crossed the old road several times between the community of Bonneville (just east of Tanner Creek) and Cascade Locks. The realignment had the effect of closing the old road to all but the most local of traffic, since the construction of the east portal of the new Toothrock Tunnel, just west of a new bridge over Eagle Creek, had destroyed a section of road on the hillside.
  By the end of the 1940s, the original cross section of 18 feet (5.5 m) of pavement and two 3-foot (1 m) shoulders had been modified to 24 feet (7.5 m) of pavement. The Mosier Twin Tunnels were similarly widened from 8⅔ feet (2⅔ m) to 10 feet (3 m) in each direction in 1938 to accommodate larger trucks, but this was not enough, and traffic signals were later installed at the tunnels to regulate one-way traffic. A 1948 bypass of the Oneonta Tunnel was made possible by moving the railroad slightly north on fill; the railroad benefited by removing the risk of the thin tunnel wall collapsing onto the track. Oneonta Tunnel was sealed in 1948 but revealed again fifty-five years later as part of the Historic Columbia River Highway restoration project.
  More comprehensive bypass planning began by 1941, when the State Highway Commission adopted surveys for the new highway.
caption: Eagle Creek Bridge
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