Part III in the series on the history of the Purdy Bridges.

The Fourth Purdy Bridge: A Design for the Ages

Completed in 1937, the bridge is an enduring reflection of that era’s engineering genius.


The first bridge over Henderson Bay between Purdy and the Wauna sandspit was built in 1892. Seemingly star-crossed almost from the outset, the structure required frequent repairs and had to be replaced twice, first in 1905 and then again in 1920-21. Timber supports were no match for the salt water and fast-moving tidal currents in the narrow channel, and its design became an early source of frustration for the growing communities in the western reaches of Pierce County.

By the 1930s the Purdy Bridge and its recurring problems had become a political thorn in the side of the county’s board of commissioners. In 1935, barely 15 years after the third bridge was built, the board and Forrest R. Easterday, the newly elected Pierce County engineer (they were elected back then, not appointed), determined it was time to replace the timber structure with one of reinforced concrete, a material more durable, less costly and requiring less maintenance.

A composite created by mixing a binder such as cement with a coarse aggregate (rocks, gravel, etc.) and water in specific proportions, concrete becomes much like stone as it cures. In the late 1800s engineers in the United States and Europe began reinforcing it by embedding steel bars or meshes to improve its strength under tension, a development that allowed them to use it in the construction of large structures such as high-rise buildings and, later, bridges. The first reinforced concrete building in the U.S. was the landmark 16-story Ingalls Building in Cincinnati, Ohio, built in 1903 and described in a 1904 article in the Seattle Times as being in effect a “complete concrete monolith.” In Tacoma, the historic 8-story Perkins Building was the tallest reinforced concrete building in the Northwest when it was completed in 1907.

Washington is home to two of the earliest concrete bridges in the U.S.: the Admiral Way Bridge in West Seattle, built in 1927, and the 3,000-foot West Garfield Street Viaduct in Seattle, also known as the Magnolia Bridge, completed in 1930. Both were designed by pioneering engineer A.W. Munster (ca. 1854-1929), at the time in his 70s but still working as a consultant for Seattle’s engineering department.

According to historian Wm. Michael Lawrence, one of Munster’s admirers was Homer M. Hadley (1885-1967), a regional structural engineer at the Seattle office of the Portland Cement Association. Portland cement gets its name from its similarity to a type of building stone from the Isle of Portland in England.

Homer M. Hadley ca. 1928
Homer M. Hadley ca. 1928

Homer M. Hadley ca. 1928.Pacific Builder and Engineer/Craig Holstine

Hadley, who would later leave his stamp on the design of several landmark bridges in the Northwest, including the Purdy Bridge, had worked during World War I building concrete ships and barges for the U.S. Shipping Board’s Emergency Fleet Corporation based in Philadelphia. He joined the PCA’s Seattle office in 1921, where he promoted the use of concrete, especially in bridges. That year, drawing on his experience during the war, Hadley proposed a floating bridge across Lake Washington between Seattle and Mercer Island, to be supported by concrete pontoons. The idea was first met with ridicule, but in 1937 received the approval of Lacey V. Murrow, the second director of Washington’s Department of Highways from 1933 to 1940, and was finally built in 1940.

Hadley was impressed by Munster’s concrete bridges, and in 1934 he suggested the design for the concrete truss McMillin Bridge across the Puyallup River in east Pierce County. As an employee of the PCA, Hadley was not allowed to work on the actual drawings himself; those were created by W.H. Witt Company, a Seattle engineering firm that had specialized in concrete buildings that turned its attention to bridges when construction slowed during the Great Depression.

In terms of engineering design, the McMillin Bridge is the precursor of the Purdy Bridge and many of the other concrete bridges in the county. A key feature is the hollow-box concrete girder, which would also be used on the Purdy Bridge. A box girder is a type of beam shaped like a hollow box with internal transverse walls to support the roadway slab above, with which it is integrated. Box girders are cheaper to build, have greater load capacity than I-beams, and are not as heavy as solid concrete, reducing the overall dead weight of the bridge.

The Washington State Department of Transportation, which now owns the Purdy Bridge, has preserved the original engineering drawings from 1935, also compiled by W.H. Witt, undoubtedly in consultation with Hadley. The bridge is 550 feet long and has five sections: a 190-foot middle span, two 140-foot shorter side spans, and two 40-foot approaches cantilevered at each end. Each span is a continuous reinforced concrete hollow-box girder. The 190-foot middle section was the longest such continuous span among concrete bridges at the time. Four piers support the five sections; the bases of the two center piers are set in deep water and into the bottom of the channel, below extreme low tide. Like the girders, the piers are also cellular in construction. The roadway, which rises and drops at a 5.8% grade, is 20 feet wide with 1-foot curbs. There was no provision for a pedestrian walk; the present sidewalk was added in 1966.

An 18-foot clearance at the middle span over the 13.8-foot extreme high tide mark allows for passage of marine traffic, as required by the Army Corps of Engineers, the same clearance as the previous fixed-span timber bridge.

The design is an example of a rigid-frame bridge, where box girders are integrated with the roadway into a single continuous structure. According to Lawrence, several engineers at the time favored that design for bridges not only for structural and economic reasons, but also because of its “clean, sweeping lines, which gave the bridges a pleasing appearance,” and is certainly true of the graceful Purdy Bridge.

While the engineering drawings date from 1935, the call to contractors wasn’t issued until July 1936. The county asked for bids for a concrete bridge to replace the existing span, a project estimated to cost about $70,000; the new bridge would replace “the wooden structure that has had to be renewed frequently in past years.”

The contract was awarded to the Portland Dredging Company of Portland, Oregon, which agreed to perform the work for $69,986.45, about $1,000 higher than Easterday’s original estimate of $68,974.48. The final cost for the project, which was titled “Secondary Road Project 51 with bridge,” came to $71,511.62, or around $1.4 million today. That amount included roadwork on the approaches to the bridge.

The bridge was closed and work began on Aug. 28, 1936; as during previous closures, traffic was rerouted through Burley. The first order of business was razing the old, 1921 wood truss bridge, an operation described in the Tacoma News Tribune on Sept. 15 as a “spectacular feat.” Using heavy cables, John A. Peabody, the superintendent of the project, and construction engineer Adron Troxell attached the two ends of the truss to the tug Elk II and at 3:30 p.m. pulled down the 120-foot span, which then “splashed into Puget Sound.” Most of the timber was probably salvaged and reused to build the temporary trestle erected at the construction site, but some of it floated away and later showed up on local beaches. The operation apparently saved the contractor $500 in time and labor, about $10,000 today.

Work was expected to take approximately four months and employ about 50 men. The crews worked for six hours instead of eight or 10, a common practice in several industries starting in the 1920s and continuing during the Great Depression as a means of spreading employment. The contractor then could add a second six-hour shift in one day if needed. Portable lights had been in use since the late 1910s, allowing work to continue after dark.

In the end construction, including all related roadwork, extended into early summer 1937. On June 3 the Tribune mentioned the need for a detour through Burley “caused by the rebuilding of the Purdy-Wauna bridge.” Work was certainly finished by September 1937, the date on the archival record for a historic photo taken by Asahel Curtis for the PCA, probably at Hadley’s request. Curtis, who was very active in the Good Roads Movement, had also showcased the McMillin bridge for the PCA.

Purdy Bridge under construction, 1936-37. Washington State Archives/WSDOT Records

Several photos from the construction, this time by an unidentified photographer, are preserved in the Washington State Archives. Among other details they show the extensive formwork required for the box girders, the enormous quantities of rebar used to reinforce the concrete and the interior of the box girders themselves with their transverse diaphragms. The photos also show the temporary trestle erected alongside the future bridge.

In contrast to the frequent press coverage of the earlier bridges and their challenges, the concrete bridge at Purdy received scant attention outside engineering journals in the decades after it was built. It was briefly noted in an article Nov. 30, 1947, listing the accomplishments of the Peninsula Civic Co-operative committee, a group consisting of 17 Key Peninsula organizations from Minter to Longbranch, which mentioned without offering any details that “fishing from Purdy Bridge has been stopped, eliminating a traffic hazard.” Several other projects are listed in the same article as “promised or under consideration by the county and state,” among them the addition of the pedestrian walk on the bridge that would finally be built in 1966.

In 1979 the McMillin and Purdy bridges were added to the Historic American Engineering Record’s bridge inventory. The HAER was established in 1969 by the National Park Service, the American Society of Civil Engineers and the Library of Congress to document important engineering sites and structures.

Three years later, in 1982, both bridges were inducted into the National Register of Historic Places. In reviewing the nomination of the Purdy Bridge, architectural historian Emma Jane Saxe wrote that “the 46-year-old bridge has exceptional importance as a rare example of a significant type and for its association with important Washington engineer H.M. Hadley.”

Now in its 85th year, the Purdy Bridge is still in service, carrying an average of more than 20,000 vehicles a day since 1990, almost double the number recorded in 1980 and ten times higher than in 1960. Although still safe, the bridge is among the 141 out of the 3,829 bridges owned by the state rated in poor condition and requiring repairs. WSDOT has been planning rehabilitation work on the bridge’s piers and beams to extend its functional life; its appearance cannot be modified, since it is on the national historic register. Initially planned for the summer of 2021, the work had to be rescheduled; a new date had not been announced as of press time.

In a May 2021 presentation to the KP Community Council, WSDOT reviewed future options for relieving congestion, currently estimated to affect traffic at the bridge 12% of the time. Those included a new bridge across Burley Lagoon near the existing span; a bridge across the shortest end of Burley Lagoon into Kitsap County; using existing county roads; or continuing to use the existing route. In 1966 the Department of Highways considered building a limited-access highway from Belfair east to State Route 16 at a point north of Purdy; that highway was never built.

The transportation bottleneck in Purdy will inevitably be resolved when funding for the environmental impact studies and construction are eventually secured. There is no obvious roadmap to obtaining that funding today, however.

Barring a natural disaster, the Purdy Bridge is here to stay, a testament to the engineering genius of its age and an echo of a time when legislatures at all levels did not shy away from infrastructure projects benefiting remote rural communities. 


Suggested reading:

Holstine, Craig. “Scarcely Orthodox: Homer M. Hadley, Washington’s Bridge Engineer Extraordinaire.” Historic Bridge Bulletin 8, no. 3 (Dec. 2021), pp. 4-8
Holstine, Craig and Richard Hobbs. “Spanning Washington: Historic Highway Bridges of the Evergreen State.” Pullman, Washington: Washington State University Press, 2005
Lawrence, Wm. Michael. “McMillin Bridge.” Historic American Engineering Record, WA-101 (Aug. 1993). Available at the Library of Congress.
Lawrence, Wm. Michael. “Purdy Bridge.” Historic American Engineering Record, WA-101 (Aug. 1993). Available at the Library of Congress.