Eagle Creek Bridge
Spanning Eagle Creek along the Historic Columbia River Highway, Multnomah County, Oregon, beginning at milepost 42.7.
Date of Construction
K. P. Billner and Lewis W. Metzger, designing engineers, Oregon State Highway Department
Pacific Bridge Company, Portland
Oregon Department of Transportation
Vehicular and pedestrian traffic
The only stone-veneered reinforced-concrete arch bridge and one of only eight arch spans on the Historic Columbia River Highway. It is the last bridge in the Multnomah County section of the Historic Columbia River Highway.
Eagle Creek Bridge
The Eagle Creek Bridge is the easternmost span on the Historic Columbia River Highway in Multnomah County, It spans a large stream emptying into the Columbia just east of Tooth Rock, which marks the crest of the Cascade Range. The HCRH’s alignment at Eagle Creek caught the attention of Oregon National Forest Service supervisor Tom Sherrard. He believed the small timbered valley, over 40 miles east of downtown Portland, was an ideal location for picnics and overnight camping for motorists.
Completed in 1915, the 25-acre Eagle Creek Campground became the first improved U.S. Forest Service camping area the country. It had a capacity of 2,000 persons at a time and attracted tens of thousands of visitors during summer months.
Design and Description
The Eagle Creek Bridge is a 100′-0″ reinforced-concrete and masonry structure consisting of a 60′-0″ three-ribbed semicircular concrete arch with 20′-0″ concrete slab span approaches and masonry abutments. Width is about 23′ with a 20′-0″ roadway. Overall length is 144′-0″. The reinforced-concrete deck is built on a grade, running from west to east at 4 percent and is covered with an asphalt wearing surface.
The arched ribs, tapered from springlines to crowns, rest on wide, flat concrete footings with only a 6″ curb to counteract longitudinal thrust. The structural system above the arch consists of three spandrel walls. These walls are made of plain square spandrel columns with intermediate longitudinal struts, and counterbraced by transverse struts. Column seats were poured as part of the extradosal surface of the arch ribs. At each end of the arch, the structure included diagonal reinforced-concrete sway bracing. The floor system, above the spandrel walls, consisted of a reinforced-concrete deck resting on both transverse and longitudinal beams, with an integrated transverse “Haunch Beam” on top of the arch ribs at mid-span.
This bridge is the smallest of the arch spans on the Historic Columbia River Highway and is the only one with a semicircular shape. It is unique among the larger reinforced concrete spans, and in particular the reinforced-concrete arches on the HCRH, because it was the only one veneered in native stone, hiding from motorists and pedestrians its complicated structural configuration. The same Italian masons who created the great variety of guard rails, guard walls, and retaining walls along the length of the HCRH also created the stonework seen on the Eagle Creek Bridge. It is possible that Samuel Lancaster suggested the use of stone veneer on this structure because it reflected design elements that he had seen in Germany and Italy during his 1908 trip to the First International Road Congress in Paris and subsequent travels to western and southern Europe to research road building. Lancaster also owned property in the vicinity of Eagle Creek and eventually built a lodge and cabins there as part of a small resort. He may have also seized the opportunity to “dress up” this bridge to compliment the design plans he had for his nearby 72 acre rustic resort, Lancaster’s Lodge.
The veneer on the east and west elevations was created from mortared random rubble basalt surrounding ashlar voussoirs. Approach span masonry consisted of 1:4 battered mortared walls. Rock courses were attached to the bridge’s concrete skeleton by a system of horizontal longitudinal anchor rods and transverse looped rods. Once masons had attached the stone veneer to the structure, they plastered the back side of the rock wall with mortar for structural stability. The railings consisted of slip joint rubble walls with regularly-spaced semi-circular arched drainage openings. They were topped with screeded concrete caps. The railing treatment provided continuity with the Historic Columbia River Highway’s standardized guard fences adjoining the bridge from the west and east.
One additional feature at Eagle Creek was a masonry pedestrian viewing platform running at right angles to the roadway near the west abutment of the bridge. It began as a large rock jutting out to the north of the roadway, but masons enclosed it with a rubble wall. Travelers could look out to the north from this safe viewing platform and see the rushing waters of Eagle Creek as it emptied into the Columbia River. Built of railings and posts similar to those on the bridge, the balcony has integral concrete benches anchored into the walls and braced by rock bracketing.
Repair and Maintenance
Maintenance records for the Eagle Creek Bridge were lost or no longer exist. The bridge itself has received only minor alterations since its construction. It was bypassed in the late 1930s when the Historic Columbia River Highway around Tooth Rock and Eagle Creek was relocated as part of the Bonneville Dam construction nearby on the Columbia River. The dam’s backwaters threatened the Oregon-Washington Railroad and Navigation Company’s mainline, forcing the company to move the rail line. This, in turn, required realigning the HCRH, bypassing the Toothrock and Eagle Creek viaducts with a tunnel through Tooth Rock and creating a new water-level route. The Oregon State Highway Department’s bridge engineer, Conde B. McCullough, and his designers, created a three-span steel through tied arch over Eagle Creek, just east of the new tunnel. The old Eagle Creek Bridge then only provided service to the nearby Eagle Creek Campground and the newly constructed Eagle Creek Viewpoint.
As part of the New Deal make-work programs of the 1930s, the Civilian Conservation Corps remodeled and enlarged the Eagle Creek Campground to include a new area north of the old bridge and the new highway alignment. It provided space for 3,000 additional campers and picnickers, and a viewpoint for observing construction on Bonneville Dam. At this point, the east masonry approach to the Eagle Creek Bridge was shortened and realigned, fanning out nearly symmetrical. This change provided motorists the ability to drive to the right (south) to the Eagle Creek Camp, or to the left (north) and under the new road and railroad alignments to the Eagle Creek Viewpoint.
Beginning sometime in the 1960s, as the realigned U.S. 30 was upgraded to a four-lane divided highway (Interstate SON, later renamed Interstate 84), the portion of the HCRH around Eagle Creek served only as an off-ramp to access the campground and a nearby fish hatchery. The hatchery, which opened in the late 1950s, has installed a manhole in the bridge deck, along with a catwalk and valve mechanism inside the structure that permits it to operate a pumping system that diverts water to its facilities.
With Bonneville Dam’s completion in the late 1930s, the unharnessed, naturally-flowing Columbia River was forever changed. The dam’s backwaters affected many streams that emptied into the river. For Eagle Creek this meant that the shallow fast-flowing brook became a deep, slow-flowing stream. Consequently, arch abutments and structural members on Eagle Creek Bridge that were never meant to be underwater for long periods are now almost continuously submerged. This, along with the passage of time, has caused some spalling on parts of the span’s superstructure.
Excerpted from Historic American Engineering Record, Eagle Creek Bridge, HAER OR-36-P.
Historian: Robert W. Hadlow, Phd., September 1995.
Transmitted by: Lisa M. Pfueller, September, 1996.