Sauk River Bridge #414 Snohomish County, Washington

Sauk River Bridge spans a federally-designated Wild and Scenic River in north Snohomish County, and at 479 feet is the county’s longest two-span, steel truss bridge. It replaces an old bridge that was built in 1930 and had become both func¬tionally obsolete and structurally deficient. The bridge was too narrow at only 18 feet curb to curb, the deck was deteriorating and there were scour problems at the piers. It needed to be replaced. Highlights

Safety Enhancements of the New Bridge Construction Excellence • The old under height, under width bridge was H• The new bridge was built in one piece on the replaced with one that is twice as wide at one side of the river and successfully rolled 36-feet. It accommodates logging trucks and above the river to its foundation on the includes generous shoulders for pedestrians other side and bicyclists • It is the first steel bridge in the Pacific NW • Scour critical pilings were replaced with a to be both hot-dip galvanized and powder- wider span foundation planted up to coated for superior paint adhesion over the 125 feet deep to avoid scour life of the bridge • The hazard of lead base coating was • A protective work platform was hung under removed with removal of the old bridge the bridge to keep debris from entering the river during the work Unique Challenges • The river’s force and migration patterns Innovative Design severely limited placement and construction • Advanced, three-dimensional modeling options for a new bridge resulted in geometric precision during • Environmental regulations disallowed fabrication of the steel structure and its temporary supports in the river successful launch over the river • The fish window for in-water workwas • Designed an educational kiosk using portion unusually tight of the old bridge to highlight its importance in the history and economy of the region • Traffic and lumber mill access had to be maintained • The existing bridge qualified for National Register of Historic Places (NRHP) which complicated the removal process Highlights

Environmental Compatibility Timeliness in Completing the Project • All components were treated, painted and • Completed 5 months ahead of schedule, heat sealed before arriving at the site to fortuitously avoiding subsequent flooding avoid environmental contamination that eroded land that had been used for staging cranes • High clearance under bridge will withstand 100-year flood and avoid logs and other Public Satisfaction/Acceptance flooding debris from upstream • Darrington residents and Mayor came out to • Longer pier spans will accommodate celebrate the opening of the bridge with the river migration project team and provided Blue Grass music and a parade of antique vehicles • Foundations are planted between 110 and 125-feet deep to withstand migration and extreme floods

Effective Project Administration • Completed 5 months ahead of time and $509,000 under budget • There were no claims • Proactive cost reduction management by Construction Manager Bob Morrison, including a $60,000 CRIP change order, saved the County more than $400,000 The community helped plan the ribbon- • Final CE/CN: 9% cutting celebration. They played blue grass • Final Engineering: $1,189,735 music and brought a parade of antique • Final construction: $13,592,219 vehicles to be the first to cross the newly dedicated bridge. Cost Effectiveness • Saved time and approximately $1 million in Awards construction costs by building in one piece H 2009 Merit Award, Iconic Bridge Category, • 3-D modeling provided accurate from National Steel Bridge Alliance (NSBA) information for ordering bridge elements H 2010 Silver Award from the American Council • Passed both FHWA and WSDOT audit with of Engineering Companies (ACEC) flying colors H 2010 American Public Works Association Enhancement of Regional (APWA) National Project of the Year Award Transportation System H 2010 APWA Washington State Chapter Project • The bridge serves as a gateway to the of the Year Award Mt. Baker-Snoqualmie National Forest and the scenic Mountain Loop Highway • Traffic averages 750 vehicles daily, 25 percent of which are heavy logging trucks Sauk River Bridge

Engineers often use precast concrete as a bridge required for this, and the contract included provisions building material to keep initial capital costs low and for preparing the river bank for the anticipated crane minimize future maintenance. In this case, however, weight. However, the contractor for the project took a conventional concrete bridge, with a relatively deep advantage of the continuous truss design and worked superstructure, would have required the roadway to with the County to implement an alternative method. be raised to maintain clearance above the 100-year flood elevation. This also would have They decided to assemble the required the roadway approaches to structure on shore, in one piece, and be raised, encroaching on the then “launch” the assembled adjacent lumber mill and making structure out over the river. An access and drainage features much innovative cantilever/roller system was more costly. used to accomplish this complex task. The trusses and framing elements were “The power of steel makes it possible first constructed on the east roadway to do heroic things, including approach. building bridges in very problem- The old bridge built in 1930, atic locations,” said the principal in was only 18 feet wide from After assembling the nearly complete charge. “By keeping the structure curb to curb. truss superstructure, launching it over light during construction, we could the river required intricate and precise minimize the profile of the roadway, control. Advance 3-dimensional model- keep the bridge surface relatively low, ing provided the calculations needed and provide adequate clearance to plan the precision work. Winches on during extreme high water flows.” either side of the trusses, designed for 25,000 pounds of line pull, guided the The Roller Launch bridge over high-capacity, low-profile, Hillman Roller dollies. Tiny deviations Historically, bridge engineers have or irregularities in the tracks would built a temporary structure on driven have produced dangerous internal piles to provide local traffic with un- friction in the rollers. Careful planning impeded and continuous travel. Also, and monitoring, however, limited the they would have erected falsework in line pulls to only 5,000 pounds, and the water to support the new bridge the bridge moved smoothly forward while under construction. However, into position without a hitch — this was not permitted in the The new bridge is twice as a masterpiece of precision. pristine, untamed Sauk River, where wide as the old, at 36 feet, construction noise and related activi- from curb to curb. To limit deflections and forces in the ties could harm endangered salmon trusses while the bridge was species and disturb their habitat. being launched, the launching method employed also required a nose piece add-on to The bridge was originally designed to be assembled successfully reach the west abutment. The project team on shore in two pieces and placed in position with designed the nose piece, something like the prow of a a special heavy lift crane. Connection of the two ship, which was then removed after final positioning pieces into a single continuous truss would be the of the truss. only assembling activities to occur over water. The team secured environmental permits to clear the land Sauk River Bridge

Galvanizing and Powder-Coating proved to be much more accurate than a conventional two-dimensional analysis of just the truss itself, and The Sauk River Bridge is the first steel bridge in the confirmed greater strength and rigidity than was Pacific Northwest to be both hot-dip galvanized and indicated by older techniques. “This was the first time powder-coated, a technique that provides much better I had seen three-dimensional modeling in actual use, paint adhesion over the life of the bridge. All steel and I was really surprised at what a big difference it members were submerged in a zinc bath at 850 de- made in accuracy,” said the construction engineer. grees, using zinc as a sacrificial anode. Then a top coat of paint was applied, and steel components were baked in a huge oven to cure the paint. Economic Benefits The project’s contractor has indicated that the deci- The dual-system process is considered to be very sion to launch the Sauk River Bridge, as previously “green,” as it requires no solvents. Top coating pre- described, resulted in an estimated construction vents the zinc used during galvanization from leaching savings of $1 million. In the end, the construction of into the pristine river below, addressing concerns from the project was completed a full five months ahead of the National Marine Fisheries Service. All rebar was the initial completion date. Construction administra- galvanized as well, a highly unusual step, providing tion staff managing the contractor’s activities have protection and inhibiting rust. Shop coating bridge stated, “The bottom line is that the County, with good components prior to shipping them to the job site defensible plans and specs, a creative and organized further minimized any possible environmental dangers contractor and good construction management was associated with applying paint in the field. able complete this project ahead of schedule and nearly $500,000 under the original bid price. There Firm Foundations were only three change orders. One was for a minor item of $1,900, another resulted in a cost reduction The project team drilled deep foundations to sup- of about $60,000, and a third was a no-cost change port the bridge to protect against scour, and because order to correct a minor contractual condition. some of the riverbank’s sub layers had a potential for liquefaction. These were 8 feet in diameter, and 110 All of this was made possible by innovative engineer- to 125 feet deep. They had to be inserted by the use ing practices, primarily the cantilevered launch, and of a special oscilla- coordinated permitting through close collaboration tor, which was too “This was the first time we’d between the project team, Snohomish County, and heavy to go across ever launched a bridge in this the: the existing bridge fashion, and it was fascinat- for placement. The ing,” said the contractor’s • Sauk-Suiattle Tribe (SST) oscillators had to be construction manager. “In • Skagit River System Cooperative (SRSC) taken apart and reas- fact, the challenge was one • Town of Darrington sembled on the other of the main reasons we went • Washington State Department of Transportation side of the river, a after the job. The creative (WSDOT) condition that was approach resulted in a safer, • Washington Department of Fish and Wildlife clearly identified in faster and more effective (WDFW) bid documents. project.” • Federal Highway Administration (FHWA) • Federal Emergency Management Administration 3-D Modeling (FEMA) • National Marine Fisheries When calculating deflections for the new bridge, the Service (NMFS) design consultants introduced a three- dimensional • U.S. Forest Service (USFS) model. It illustrated stiffness of the structure, includ- ing lateral bracing of both the top and bottom. This Sauk River Bridge

Financial support from a Conservation Futures grant The New Sauk River Bridge helped pay for purchases of properties upstream from the bridge, which are being maintained as a passive A tribute to its breathtaking natural surroundings, park by the Town of Darrington. Federal bridge the new Sauk River Bridge has achieved one of its Replacement funds (BROS) and County Road Fund toughest challenges: to be an aesthetic match to the dollars paid for construction of the bridge. beautiful scenery and its inhabitants

No one could have anticipated another odd source of Aaron Reardon, Snohomish County Executive financial savings. Right after the bridge was finished, John Koster, Councilman, District #1 major flooding occurred. The rushing waters eroded land that had been used for staging cranes while Snohomish County Public Works Administration removing the old bridge. If the new bridge had not Steve Thomsen, Director been finished early, and therefore the old one also Owen Carter, County Engineer demolished early, the County would have faced consid- Art Louie, Engineering Services Division Director erable additional expense. Project Team: Aesthetic Considerations Jeri Bernstein/Kinyan Lui, Project Management Bob Morrison, Design & Construction Engineer The original Sauk River Bridge was one of a select Crilly Ritz, Environmental Planner type of steel bridge, and very few of its age remain in Celia Eizik, Construction Inspector the state. When replacement became inevitable, the Mike Zitkovich, Construction Inspector County completed initial Historic American Engineer- ing Record (HAER) documentation on the bridge, in BergerABAM, Bob Fernandes accordance with National Historic Preservation Act Mowat Construction, Ryan Olson Section 106 requirements and designed an educational Rainier Welding kiosk that highlights the bridge’s place in the history Marshbank Construction and economy of the region. WSDOT: Ed Conyers, Sam Schuyler FHWA: Elizabeth Healy

Photos: Ramon L. Mañano

The bridge serves as a gateway to the Mt. Baker-Snoqualmie National Forest and the scenic Mountain Loop Highway.