What is now State Route 142 in South Central Washington was built by Klickitat County in the mid-1930s to connect Lyle, on the Columbia River, with the county seat at Goldendale, some 24 miles east as the crow flies. Approximately 17 highway miles northeast of Lyle, the road crosses the Klickitat River on two bridges that meet on a small island that is formed when the river runs high. The first bridges at that location, built in 1934, were timber trusses. These were replaced in 1955 by bridges designed by Seattle engineer Harry R. Powell (1901-1991), an early advocate for a technology nearly new to America -- prestressed concrete. The bridges that Powell designed for that site marked the first use of the material by a county agency in Washington and are of some historical significance. In 1974 the western span (designated 142/8) was washed away by a flood and replaced. By 2012 the eastern span (142/9) was deemed no longer safe for use, and a one-lane temporary bridge was installed over it. In mid-2016 this was dismantled, the 1955 span demolished, and a new, prestressed concrete bridge built in its place.
The Region
Long before their first contact with non-Natives, the area that is now Klickitat County was home to Klickitat Indians, a name derived from a Chinook word meaning "beyond," i.e., beyond the Cascade Mountains. The Klickitats were skilled horsemen, hunters, and traders, and noted for the intricate basketry women wove.
The Klickitats were one of 14 tribes that Territorial Governor Isaac Stevens (1818-1862) grouped together as Yakama (Yakima) at the Walla Walla Council in 1855 that established the Yakama Reservation. After moving to the reservation, they largely assimilated with the Yakama, and by 1970 there were only 21 self-identified Klickitats recorded as living in the state.
The County of Clickitat (spelled Klickitat since 1869) was created by the Washington Territorial Legislature in 1859, although its borders were not permanently settled until 1905. At the time of its formation only about 15 non-Indian families resided there. Klickitat County is about 84 miles wide and abuts Skamania County to the west, Yakima County to the north, and Benton County to the east, with its southern border defined by the Columbia River. In 1878 Goldendale became the county seat.
The region's early economy centered on cattle and sheep, but by 1900 much rangeland had been converted to agriculture, mostly wheat, oats, barley, and fruit. Timber, until more recent years, was also an economic mainstay. Early logging primarily provided fuel for Columbia River steamboats, but by 1903 Klickitat County had 23 lumber mills and seven mills producing shingles, rail ties, and finished wood.
Two of Washington's six designated Wild and Scenic Rivers are located in Klickitat County: the lower White Salmon River where it flows through a nine-mile canyon between Gilmer Creek and Northwestern Lake, and the Klickitat River from near the community of Pitt to the confluence with the Columbia. These are preserved in their natural free-flowing state and protected by federal law. The Klickitat remains one of the longest undammed rivers in the Pacific Northwest.
Rivers, Trails, Rails, and Roads
Klickitat County in its early days had few transportation options other than rivers and trails. In the mid-1850s a military wagon road was built between Fort Dalles on the Columbia and Fort Simcoe in the Yakima Valley, but it became unusable not long after federal troops left in 1867. The county's first overland mail-stage route was built from Rockland (now Dallesport) through the Klickitat Valley and Satus Canyon in 1868, but keeping it passable in winter was an annual, often futile, ordeal.
In 1903 the Columbia River and Northern Railway opened a line between Goldendale, near the center of the county, and Lyle on the Columbia. In 1908 James J. Hill's (1828-1916) Spokane, Portland, and Seattle Railway began providing service along the north bank of the Columbia, and soon took control of the Lyle-to-Goldendale track as a branch line.
By 1926 State Highway 8 (the North Bank Highway) was completed from Goldendale to Vancouver in Clark County. The north/south portion later became part of US 97, which intersects the remainder of Highway 8 north of Maryhill. The route continues west to Vancouver, running next to the Columbia River most of the way. In 1967 this scenic two-lane road was designated State Route 14 (Lewis and Clark Highway) and is part of the Lewis and Clark Trail, a linked system of federal and state roads that approximates the path between the St. Louis area and the Pacific Ocean taken by the explorers in the early 1800s.
State Route 142
In 1934 Klickitat County began building a highway to link Goldendale and Lyle. Until the state took it over in the early 1960s as Secondary State Highway 8E, it was apparently known only as the Goldendale-Lyle Road. In 1970 the legislature designated it State Route 142 (SR 142), and for the sake of clarity it will be referred to by that name throughout. A terrain of steep slopes and forested hillsides provides scenic views along its 35-mile course but discourages development, and the corridor remains sparsely populated for much of its length.
The entire length of SR 142 lies in Klickitat County. From Goldendale the highway travels westward about 16 miles to reach the Klickitat River, then follows the river's south bank for a short distance. About four highway miles east of the town of Klickitat two linked bridges carry it to the north bank. When the river's level is high at this location, it creates a second, eastern arm that carves out a small island. One bridge (142/9) crosses this overflow channel and a nearly identical span (142/8) carries traffic between the island and the river's opposite bank.
In 1934 the county's bridge builders had ample timber close at hand, and each of the original bridges comprised two timber trusses -- a 49-foot Queen Post truss and a 91-foot Howe truss. The Queen Post truss design, one of the simplest, probably dates back to at least medieval times. Howe trusses were considered the apotheosis of wooden-bridge building in the late nineteenth century, simple, sturdy, and often used by railroads. But the science of steel bridges was well-established by 1934, so cost considerations no doubt dictated the use of timber.
Because of their close similarity, the two structures were soon dubbed the Twin Bridges, a natural impulse but one that can still cause some confusion. Just a year earlier and about 17 highway miles away in Lyle, a graceful concrete-arch span was built in 1933 to carry SR 14 across the Klickitat River at its mouth. Nearby was a smaller railroad bridge of similar construction, built in 1908. These also became known as the Twin Bridges, and the Twin Bridges Museum in Lyle is named for them, not the spans that are the subject of this article.
A major drawback to timber trestles was high maintenance requirements and lack of longevity, and within 20 years the bridges were nearing the end of their useful lives. When planning began in 1953 for their replacement, more state and federal funding was available to help counties build roads and bridges than in the past. Early that year Klickitat County's road engineer, William T. Cavanaugh (1884-1964), called upon a well-known structural engineer from Seattle, Harry Robert Powell, to develop proposals for replacing the aging timber trusses.
Harry Powell, Bridge Engineer
Harry Powell was born in the tiny town of Grenfell, Saskatchewan, and raised in Regina, the provincial capital. He graduated from the University of Toronto in 1922 with a degree in engineering, specializing in hydraulics and reinforced concrete. In 1925 he came to Seattle and, while living at the YMCA, opened a structural-engineering practice with a fellow Canadian, Verney Stewart (1898-1980), in the Empire Building at 914 2nd Avenue. In 1927 he and Stewart parted ways, and the following year Powell opened a solo engineering practice in the Thompson Building at 621 4th Avenue. By this time he had been joined in Seattle by his wife, Eileen (1892-1991).
When he was approached by Klickitat County, Powell had been a practicing engineer for more than 25 years and had ample experience designing buildings and bridges using timber, steel, or concrete. After consulting the state Department of Highways and the federal Bureau of Public Roads, both of which were providing funding, Powell prepared three proposals. The second and third specified cast-in-place concrete box-girder bridges, with the second ($60,000) proposal using the existing concrete piers and abutments from the worn-out timber spans, and the third ($70,000) calling for their replacement.
Powell's first suggestion was more adventuresome. Rather than cast-in-place girders, this called for precast girders that would be formed elsewhere, transported to the site, placed on the existing piers and abutments, then prestressed using a post-tensioning technique. As explained in greater detail below, post-tensioning is a method of prestressing concrete to increase its strength under loads. The estimated cost for this option was the highest, at $80,000, as calculated by the state highway department and the Bureau of Roads.
The least-expensive proposal (cast-in-place girders on existing piers) was initially selected, but Powell was invited to provide additional information in support of an alternative. As one of the few structural engineers in the country who had experience using prestressed concrete, he was well-positioned to do so.
Concrete: Lost and Found
Concrete and cement are not the same thing. Cement is a fine binding powder, most often made of limestone and clay, that is combined with water, sand, and gravel to make concrete. Concrete with similarities to modern formulations was used by the Romans as early as 300 BCE, but after the fall of the Roman Empire the technology, remarkably, was lost for nearly 1,300 years. It was gradually rediscovered beginning in the mid-eighteenth century, primarily in Great Britain.
A major advance came in 1824, when Joseph Aspdin (1778-1855), a bricklayer in Leeds, patented what he called Portland cement, named for the Isle of Portland off England's south coast. He made it by burning powdered limestone and clay in his kitchen stove. When mixed with sand, gravel, and water it formed concrete. Almost all concrete used today is made with Portland cement (yet there remains disagreement about whether the "P" should be capitalized). About 10 billion tons of concrete are produced every year, and it is considered one of human history's key inventions. Life as we know it would not exist without concrete. Cities and towns are built of it, many roads are made of it, and the only substance on earth we use more of than concrete is water. So fundamental has it been to human progress that Microsoft founder Bill Gates (b. 1955), on his personal blog, wrote an admiring entry in 2014 titled "Have You Hugged a Concrete Pillar Today" (Gatesnotes).
Reinforced Concrete
As useful as it has been, simple concrete has limitations. It is extremely strong when compressed, but is particularly vulnerable to tensile (stretching) forces, a problem of great significance to bridge design. Under heavy weight, the upper part of a horizontal concrete beam is compressed as the beam bends under the load. But the lower part of the beam is simultaneously being stretched, or pulled apart. This leads to cracking, weakness, and potential failure. This frailty can be offset to some degree by increasing the size of the concrete beams or girders, but the trade-off is increased weight and greater material costs. The longer the span, the more serious the problem becomes and the more unacceptable the compromises.
In the last few decades of the 1800s, the process of strengthening concrete with embedded steel reinforcing bars, commonly known as rebar, came into wide use, beginning in France. In this application, the steel helps bear the stretching forces of tension. In concrete-girder bridges, typically, a webbing of connected rebar is constructed within a form at the bridge site, over which concrete is then poured. This was the method called for in Powell's second and third proposals to Cavanaugh. The use of steel rebar lessens, but does not eliminate, concrete's vulnerability to tensile forces.
Prestressed Concrete
Most simply stated, prestressing involves using compression to induce internal stresses in a concrete structure that will counteract the tension stresses induced by external loads. Remarkably, the method did not come into use in the United States until 1950, nearly 25 years after it had been largely perfected, again in France.
Exactly when the idea of prestressed concrete first appeared remains a subject of debate. Europeans and a few Americans had been experimenting with it as early as the mid-nineteenth century, but it was Eugène Freyssinet (1879-1962), a French civil engineer, who is credited with perfecting the technology. Freyssinet began his bridge-building career using reinforced concrete, and in 1926 he designed the Plougastel Bridge across the Elorn River at Brest, the longest reinforced-concrete bridge constructed to that time. He then turned his attention to prestressed concrete, and with that earned an honored place in the annals of engineering innovation. On October 2, 1928, Freyssinet and a colleague registered the world's first patent for prestressed concrete.
Prestressed concrete really came into its own in Europe immediately after World War II, when hundreds of destroyed bridges had to be replaced at a time when structural steel was in short supply. It was not until 1951 that the building of the Walnut Lane Memorial Bridge in Philadelphia marked America's first use of prestressed concrete in a long span. Over the next few years, prestressed concrete became a material of choice for many applications, and Harry Powell was one of the first structural engineers in the country to become adept in its use.
Pre-Tensioning and Post-Tensioning
There are two basic methods of making prestressed concrete beams, girders, and slabs -- pre-tensioning and post-tensioning. While the processes are relatively easy to explain, they are highly technical in practice and entail detailed engineering calculations and materials expertise.
Pre-tensioning is accomplished by stretching and anchoring cables, called tendons, in a form before the concrete is poured. Cables are laid along the longitudinal axis of the component that is being made, then stretched using hydraulic or pneumatic jacks. When the concrete is poured, the tendons become bonded to it throughout their length. After the concrete has hardened, the tension is released and the wires tend toward shortening to their original length. The concrete in which they are embedded is pulled along with them. This compresses it and helps offset the tensile forces caused by heavy loads.
Post-tensioning, as the name indicates, occurs after the concrete has been poured. While the concrete form is being built, hollow tubes called ducts are added along the axis to be tensioned. The cable tendons run through the ducts and initially are anchored to a plate at one end. After the concrete is poured and has sufficiently cured, the tendons are stretched from the other end, again using powerful jacks. The ducts carrying the tendons are filled with grout, which not only protects the tendons from corrosion, but also binds them to the concrete along their length. As in pre-tensioning, the stretched tendons exert compressive force when released that offsets the tensile forces to which the structure will be subjected.
Powell's Pick
On May 5, 1953, Powell responded to the invitation to comment further with a spirited argument in favor of using prestressed concrete girders, with the components built off-site and trucked to the Klickitat River location for assembly. Among the advantages he claimed were a greatly reduced construction schedule and the convenience and savings of building the girders at a place where the necessary materials and labor were readily available. He also provided estimates by his firm showing that the cost would not be $80,000, but rather very close to the $60,000 option that initially had been selected.
Powell followed this up three days later with a glowing review from the Albion Creek Logging Company of a precast, prestressed concrete bridge he had designed for it earlier that year. Called the Burma Bridge, it crossed the Calawah River in Clallam County, and "carried loaded logging trucks, traveling bumper to bumper, without a quiver" (Boswell and Krier, 15). An earlier precast, prestressed concrete bridge Powell designed for the Anderson and Middleton Logging Company to cross the Humptulips River in the Olympic National Forest appears to have been the very first bridge in the state to use the technology, and it also had performed well.
Powell's arguments prevailed. The county, the state, and the federal government all agreed to accept his recommendation, and his firm went to work finalizing the design.
The Anderson Brothers
It was a happy coincidence that in 1953 Washington, among only a handful of places in America, had both a structural engineer who understood the process and the benefits of prestressed concrete and a facility with the expertise to produce it. The latter was the Concrete Engineering Company of Tacoma, whose owners, brothers Arthur (1910-1995) and Thomas (1912-2000) Anderson, were MIT-trained engineers.
Arthur Anderson had been involved in testing the girders used in the Walnut Lane project, and the experience convinced him of the advantages of prestressed concrete. In the fall of 1950 the brothers and their father, a contractor, traveled to Europe to investigate further. Upon their return in 1951 Arthur and Thomas formed Concrete Engineering, and what they called their "Pilot Plant" was one of the first totally precast, prestressed buildings in North America. The company's position in the vanguard of the new technology was affirmed with the development of the Anderson Post-Tensioning System, which would be used on the SR 142 project.
The two bridges that Powell designed would each have a long and a short section, with five 90-foot precast and prestressed concrete I-beams for each longer section and five of 47 feet, 7 inches for the shorter. In most concrete-girder bridges, the roadway rests on the top flange of the I-beams. For reasons that are not entirely clear, Powell's design called for the bridges' concrete roadbeds to be poured between the flanges, rather than resting on top of them. This was not a design repeated in later projects, and it may have contributed to the severe deterioration of the roadbed on Bridge 142/9.
Building the Bridges
Building 10 precast, 90-foot-long concrete girders was not a technical problem, but transporting them in one piece on the winding and relatively narrow road leading from Lyle to the bridge site would be impossible. Powell's plans specified that the long girders would be poured in three segments, each 30 feet in length, separated by divider plates the Andersons devised. The three forms for each of the 90-foot segments would be built end to end and include six ducts for tensioning cables that ran continuously from the first through the third segment. The ducts, in this case rubber hoses 1.5 inches in diameter, were withdrawn 16 hours after the concrete was poured, leaving channels through which the tensioning cables would be threaded at the bridge site. There the three 30-foot segments for each I-beam would be laid end-to-end, supported by falsework and the existing foundations, to form a single, 90-foot girder.
While the I-beams were being prepared in Tacoma, demolition of the timber trusses was underway on the Klickitat River. The tops of the reinforced-concrete piers, which rested on concrete spread footings, were modified somewhat to accept the new girders. By the time the girders arrived after a long road trip, all was ready for their installation.
Using cranes and muscle, workers positioned them in place on the temporary falsework. The tensioning cables were then fed through the holes created by the ducting. Each cable comprised eight 3/8-inch-diameter strands. The top four cables, arranged in a vertical row, were all draped, following a downward-curving path from one end to the other, 90 feet away; the bottom two cables, arranged side by side on the I-beam's bottom flange, followed a straight line through the concrete. Jacks were used to tension the cables to the prescribed load, after which cement grout was pumped into the ducts, binding the cables to the surrounding concrete. When the tension was released and the cables sought to return to their original length, the three 30-foot segments were forced together in compression and behaved structurally as a single, 90-foot girder. The shorter, one-piece girders were prepared in a similar way. After the post-tensioning was complete, the roadbed and curbing was poured and the spans completed without undue complication.
1955-2016
The new bridges opened for traffic on February 17, 1955, an event that Cavanaugh declared marked "a new era in public bridge building" (Boswell and Krier, 28). They were the largest prestressed-concrete bridges yet built in the state and the first use of the material on one of Washington's public roads. Fifteen years later the spans were inspected and found to be in good shape, but in January 1974 much of the western bridge (designated 142/8) was washed away by heavy flooding. It was replaced the next year using new precast, prestressed concrete girders.
Harry Powell earned wide acclaim for bridge designs in both concrete and steel. In 1962 the American Institute of Steel Construction honored his steel-girder Skykomish River Bridge at Sultan as the best in its class. It was just the latest of several awards, and an article in The Seattle Times, quoting a trade publication, noted "Probably no engineer in the nation can equal his record in winning four national and one international prizes for his bridge-design work in the last three years. Most engineers would be happy to win one such contest in a lifetime of bridge designing" ("A Bridge Can Be Beautiful").
Another of Powell's winning designs, and a public favorite, is the graceful Rainbow Bridge over the Swinomish Slough at La Conner, another steel construction. In fact, all five steel bridges that Powell designed before 1963 won prizes, yet during the same period he designed at least 40 concrete bridges and an equal number built from timber.
The Andersons' Concrete Engineering Company was eventually spun off as the Concrete Technology Corporation, to delineate between the materials and the engineering aspects of their operations. The company prospered with the widespread adoption of prestressed concrete. Still based in Tacoma as of 2018, it has built thousands of concrete bridges, buildings, piers, tanks, floats, and other structures throughout the Pacific Northwest and Alaska.
An inspection in 1985 showed that Bridge 142/8, replaced after the 1975 flooding, remained in good shape, but that the deck slab on the eastern portion, Bridge 142/9, had badly deteriorated. Much of the deterioration was attributed to pouring the deck slab between, rather than atop, the top flanges of the girders. In 1993 three proposals were drawn up. The best option was determined to be a full replacement of the span, and planning began.
That proved to be a lengthy process, and the bridge continued to deteriorate. In 2002, Bridge 142/9 was determined eligible for listing in the National Register of Historic Places, but by 2012 it was no longer safe for heavy loads. To buy time the state erected a temporary structure, called a Bailey bridge, atop the span. It was supported on the existing piers, removing all weight from the old structure, but was only wide enough to allow one vehicle at a time. Weight restrictions were still needed, but it kept the important highway link open.
Because of its historical significance, various proposals were considered to save the original structure, but none were found feasible. Finally, in late June 2016, the Bailey bridge was removed and a huge, track-mounted jackhammer reduced Bridge 142/9 to rubble, clearing the site for construction of a new span, built, as was its predecessor, of precast, prestressed concrete.
