Horsetail Falls Bridge
Spanning Horsetail Falls Creek, in Multnomah County, Oregon, on the Historic Columbia River Highway, beginning at milepost 34.6, in Multnomah County, Oregon.
Date of Construction
K. P. Biliner, designing engineer, Oregon State Highway Department
The Construction Company, Portland
Oregon Department of Transportation
Vehicular and pedestrian traffic
One of two nearly identical reinforced concrete girder trestles on the Historic Columbia River Highway and one of four extant structures on the route that have a distinctive cap and arch concrete guard rail system.
Horsetail Falls Bridge
The Historic Columbia River Highway’s alignment from Crown Point, milepost 23.9, to Horsetail Falls Bridge, milepost 34.6, takes the highway along one of the largest concentrations of high waterfalls in North America. Near the eastern end of this section lies Horsetail Falls, a 176′ cataract that looks like the tail of a giant white horse. It drops off a basalt cliff immediately to the south of the HCRH, misting the roadway. It ends in a pool that continues on to form Horsetail Falls Creek, passing under Horsetail Falls Bridge as it makes its way to the Columbia River. The name “‘Horsetail Falls’ has been in use since pioneer days in Oregon,” according to the compiler of Oregon Geographic Names, and is purely descriptive of the site.
During the Historic Columbia River Highway’s construction, K. P. Billner, designing engineer for the Oregon State Highway Department, created plans for several bridges for the Multnomah County Road Department, including Horsetail Falls Bridge. His plan called for a 60′-0″ reinforced-concrete deck girder trestle, similar in design to the Oneonta Gorge Creek Bridge, one-third of a mile to the west on the HCRH.
Design and Description
The Horsetail Falls Bridge is a three-span 60′-0″ reinforced-concrete deck girder trestle. It is 24′-0″ wide and has a roadway measuring 22′-0″ curb-to-curb. The curb and guardrail form an integral unit, cantilevered out from the girder. The curb and square endposts have bushhammered inset panels. The railing takes the form of 12″-wide slender concrete plaster aches, spaced two per span, with beveled rail caps, and interrupted by 12″-square chamfered and capped posts. Reinforcing wire was used in the rail caps, while metal “hybrid” lath was used in the plaster arches. This design is common on the Historic Columbia River Highway, and is found on the West and East Multnomah Falls viaduct, and Oneonta Gorge Creek Bridge. It was also seen on at least one other structure on the HCRH, a short viaduct that existed west of Vista House and Crown Point Viaduct.
Difficulty in finding firm pier foundations in Horsetail Falls Creek’s wide, flat, and gravelly stream caused K. P. Billner to design a structure with a series of small piers, or a “pile trestle,” as he labeled it. Five sets of piling were sunk below the streambed to bedrock with a small, 300 to 400 pound horse-powered hammer. The many small piers dispersed the bridge’s dead and live loads without a heavy concentration at just a few places. The piling was cut off below the streambed’s surface and the footings for the reinforced-concrete trestle piers were placed on top of them. Under the outer spans, Billner had the stream bank riprapped at a 1^’:1′ slope to protect it from erosion. The Construction Company received the contract for Horsetail Falls Bridge on March 12, 1914 and completed it by 1 October 1914 at a cost of $1,819.70. It used 123.4 cubic yards of Class A (1:2:4) concrete .
Repair and Maintenance
Maintenance records for the Horsetail Falls Bridge reveal little about repairs made to the bridge since its construction. It appears structurally sound. In the early 1990s, an Oregon Department of Transportation mason recast the concrete plaster arch and cap guardrail on both viaducts as part of a long-term rehabilitation program for historic road resources along the HCRH.
Excerpted from Historic American Engineering Record, Bridal Veil Falls Bridge, HAER OR-36-M.
Historian: Robert W, Hadlow, Ph.D., September 1995
Transmitted by Lisa Pfueller, September 1996