Earlier this year, citizens in rural Lewis County, Washington, celebrated the opening of a brand-new bridge spanning the South Fork Newaukum River at State Route 508. Located approximately 5 miles east of the Onalaska community, this river crossing carries an average of 1,400 vehicles per day and serves as a vital connector for motorists traveling between Interstate 5 and U.S. Route 12. The modern pre-stressed concrete structure was built to replace an aging pony truss bridge that had become functionally obsolete after nearly a century of use.

“The opening of the replacement S.R. 508 South Fork Newaukum River Bridge is a win-win for Washington’s future and our past,” Project Engineer Joanna Lowrey, PE, Washington State Department of Transportation (WSDOT). “The new structure is more functional, meeting current engineering and safety standards, while the old bridge will be preserved, maintaining a piece of Washington state’s transportation history.”

Building Better, Stronger

For the last three months, SR 508 travelers have enjoyed unrestricted access to the new-and-improved Newaukum River crossing. Substantially completed on April 4, the $8.5 million project was led by Oregon State Bridge Construction, Inc. (OSBC), a general contractor based in Stayton, Oregon.

The replacement bridge is 32 feet wide and 225 feet long and features two 12-foot lanes with 4-foot shoulders. The structure was built on a new alignment south of the former bridge and designed with a less-severe curve than the existing alignment to enhance traveling safety. Constructed 3 feet above the 100-year flood elevation, it features a drilled shaft substructure and concrete girders engineered to better withstand heavy traffic loads, flooding, and earthquakes.

Crews built two precast concrete spans – a 70-foot-long span bridging the floodplain adjacent to the river, and a 155-foot-long span bridging the South Fork Newaukum River. The wide-flange, thin-deck girders are topped with an additional 10.5 inches of concrete deck.

During design phases, one major concern involved the increasing erosion of the area’s riverbank. “We had a few damaging winter storms prior to construction, which changed the shape of the riverbank,” Lowrey explains. “One drilled shaft that was originally intended to be above the riverbank was now exposed to the water. We addressed this challenge with a change order that included streambed isolation, a drilling platform and permanent shaft casing.”

The project team utilized a variety of heavy machinery to erect the replacement bridge and dismantle the substructure of the existing one. The array of cranes included: a 50-ton Grove RT 745 and a 275-ton Grove GMK5275; a 260-ton Zoomlion QUY260; a 365-ton Liebherr LTM 1300-1 and a 200-ton Liebherr HS 883 HD; a 130-ton Link-Belt ATC-3130; and a 100-ton Kobelco CK1100G.

For the new structure, OSBC used a Linkbelt 370LX to perform excavation work while the drilling subcontractor employed two Leffer VRM-series hydraulic casing oscillators to drill the bridge shafts. A total of six shafts were required for the foundation, each one 8 feet in diameter and drilled to depths ranging from 60 to 75 feet.

The drilled shafts were installed in June and July 2018, followed by the placement of the girders in early October and the bridge deck in November. Crews halted work temporarily during the snowy winter months, but by early April 2019 had completed the subgrade and base-level paving and installed traffic barriers.

“In late April, the existing bridge trusses were lifted from their foundations, cut apart and loaded on trucks for the move to their new home,” Lowrey says. “The remaining work on this project consists of landscaping, establishing wildlife habitat areas, riverbank protection, and removing other existing items.”

The major subcontractors on the project team include Catworks Construction, which primarily handled embankment and earthwork activities, and Malcom Drilling Company, Inc., which drilled the bridge shafts. Other key contractors are: Cascade Concrete Sawing & Drilling, Jammie’s Environmental, Inc., John Wayne Construction, Shannon & Wilson, Inc., ACS Testing, Inc., Axis Crane, LLC, C&R Tractor and Landscaping, Inc., Willamette Valley Steel, American Concrete Company and Petersen Brothers, Inc.

Protecting a Regional Landmark

During the first half of the 20th century, pony truss bridges were often used to span short distances. As concrete girder bridges gained in popularity, pony trusses have become relatively rare. Before it was retired, the original SR 508 South Fork Newaukum River Bridge (built in 1930 by general contractor Creech Bros. Contracting Co.) was one of only 13 pony truss bridges over 50 years old remaining on public roadways or recreation trails in Washington.

“The main issue with the existing bridge was loss of strength due to corrosion. Also, it did not have sufficient clearance above the 100-year flood elevation,” Lowrey says. “The existing bridge had taken some hits from large trees and logs traveling down river during high flood events. On occasion our maintenance crews would have to remove log jams against the upstream end of the bridge.”

In addition to local traffic, a number of freight carriers hauling lumber use the SR 508 South Fork Newaukum River crossing. In an effort to extend the usable life of the existing bridge, in July 2012, WSDOT reduced the 15-ton weight limit to 7 tons. Also, commercial traffic was detoured to U.S. Route 12. Despite these traffic restrictions, overweight loads continued to cross the aging structure, which accelerated the bridge’s deterioration – particularly the deck steel.

“Following a January 2015 safety inspection, we closed the bridge because it could no longer support heavy loads,” Lowrey says. For the safety of the traveling public – and to keep this important travel connection open – WSDOT installed a single-lane Bailey bridge on top of the existing bridge for travelers to use temporarily until a new bridge could be constructed.

Instead of simply demolishing the old pony truss structure, WSDOT conducted a nationwide search to find a new owner committed to preserving the regional landmark, which was eligible for listing on the National Register of Historic Places.

“Given the condition of the steel floor system, we were unsure if anyone would want to spend the time and money to rehabilitate the structure, or even be able to take it apart safely for transportation,” says Tamara Greenwell, a Communications Specialist for WSDOT. “In collaboration with our state’s historical preservation office, the Department of Archaeology and Historic Preservation (DAHP), as well as with the U.S. Army Corps of Engineers and internal stakeholders, we assessed whether or not it was reasonable to market the bridge.”

WSDOT also consulted with personnel from the Historic Bridge Foundation (HBF), a national organization that advocates for the preservation of historic bridges in the United States. “The HBF folks, along with the DAHP, encouraged us to give it a try. We did a lot of research to identify the most efficient ways to market the bridge and find a new owner. Once we determined that it was reasonable, marketing the bridge was a condition of our environmental permitting for this project,” Greenwell says.

The timing of the initial marketing push in late 2016 just happened to coincide with the Black Friday shopping season.

“We had a lot of fun tying it into Black Friday and holiday shopping. I think we got a little bit more coverage from media organizations because of the timeliness and sort of cheekiness of the blog post we wrote to publicize it,” Greenwell says. “The old rusty bridge was touted as ‘the gift for the person who has everything.’”

The six-month campaign resulted in media coverage throughout the West Coast – and even gaining attention in Canada. A dozen respondents vied for ownership of the riveted-steel, 90-foot Warren pony trusses with verticals (the bridge deck and substructure were not part of the package). Ultimately, Ian Winterbourne won the historic gem and, on April 19, had the 90,000-pound structure transported to his private property in Walla Walla, Washington, where he intends to install it across a creek.

For WSDOT, preventing this iconic structure from being turned into scrap metal is a defining accomplishment. “This is the first time our agency has successfully rehomed a historically significant bridge,” Greenwell notes. “The history of the bridge will be preserved locally through an exhibit at the Lewis County Historical Museum, where WSDOT has donated the bridge plaques.”

Currently, WSDOT is working to find a new home for another significant structure – the Meridian Street Bridge once used to ferry SR 167 traffic over the Puyallup River. Built in 1925 and decommissioned in 2015, this 371-foot-long, 24-foot-wide, 379-ton bridge served as a portal for cities along the Puget Sound to the semi-rural, agricultural community of Puyallup, Washington.