The Murray Morgan Bridge was massive for its day, with a 200 ft wide channel and an impressive 135 ft high clearance when raised. Courtesy of City of Tacoma
Tacoma marks the 100th anniversary of the Murray Morgan Bridge by unveiling a rehabilitation that gives the span a new lease on life.
February 26, 2013—For several decades, it was unclear if the Murray Morgan Bridge in downtown Tacoma, Washington would mark the 100th anniversary of its February 15, 1913, opening by still dramatically spanning the Thea Foss Waterway—or rusting in pieces in a scrap yard. Ultimately, preservation won.
In 2009, the Washington State Department of Transportation (WSDOT)—having rerouted State Route 509 onto a new cable-stayed span in 1997—negotiated to return of ownership of the bridge to the City of Tacoma, complete with the $26.3 million the state estimated it would cost to demolish it and an additional $11.2 million.
It was a homecoming for the bridge, which was built by the city for $600,000 in 1913. City leaders, keen to preserve the highly identifiable structure, had already approved a feasibility study to determine if the bridge should be saved and the likely cost of such a project. The city hired David Evans and Associates, in Tacoma, for the study.
“At the point it was turned over to the city, it was in really bad shape,” says Steve Shanafelt, P.E., M.ASCE, an associate professional engineer with the firm. “We did a feasibility study on whether or not the bridge could be salvaged. It was our conclusion that it could be, and the city’s conclusion that they wanted to pursue it because it is an historic structure.”
The Murray Morgan Bridge, seen here framing Mount Rainer in
1947, has been a fixture in the Tacoma skyline since 1913.
urtesy of Tacoma Public Library
The Murray Morgan Bridge was designed by famed bridge engineer John Alexander Low Waddell of Waddell & Harrington, Kansas City. Waddell is credited with the design of more than 1,000 structures during his career. He was known for his robust designs, often employing 20 to 50 percent more steel than his contemporaries.
The bridge was massive for its day, with a 200 ft wide channel. When two large motors were engaged, the lift span raised 75 ft in 30 seconds, providing an impressive 135 ft high clearance between the lower chord and the water at high tide. Closed, the bridge provides 60 ft clearance. It was a vital transportation link for workers in the factories and port terminals in the tidelands area. Some of these workers went to work on streetcars that utilized the span to cross the Thea Foss Waterway.
Today, the bridge provides a vital link between the East Foss Peninsula and the Port of Tacoma for emergency responders. It also plays a key role in ongoing revitalization efforts that are converting the former industrial area into waterfront development complete with condos, museums, parks, and marinas.
As the city was conducting the feasibility study about rehabilitating the span—which was added to the National Register of Historic Places in 1982—the WSDOT closed the bridge following an inspection in 2007, citing safety concerns.
“In our analysis, we discovered the bridge hadn’t been painted for 25 years,” Shanafelt says. “It looked really bad. I actually walked the bottom chord of this bridge and the gusset plates, several of them, literally had holes through them.”
Shanafelt says a combination of deferred maintenance, the harsh saltwater environment, nesting birds, and standing water led to the serious corrosion issues on the gusset plates. Of the 100 plates, perhaps a dozen were rusted through.
“However, when we analyzed the bridge, we concluded that really it wasn’t as bad as it looked, Shanafelt says. “There was a lot of structure left. We were convinced ... you could have repaired the gusset plates and the bridge could be reopened to traffic. We wouldn’t advise it. We were just trying to point out that the bridge was not this total waste of steel that the state felt that it was and that much of the public believed that it was.”
The bridge plays a key role in ongoing revitalization efforts that
include the development of condominiums, museums, parks, and
marinas. Courtesy of City of Tacoma
With the decision made to rehabilitate the bridge, the key question became how? The city was able to obtain a federal loan to complete the $57-million funding for the project. Because the bridge was no longer carrying Route 509, the four-lane deck could be reduced to two lanes for traffic, decreasing live loads. This enabled engineers to repurpose deck space for bicycle lanes and new sidewalks. The original sidewalks—cantilevered off the sides—were removed, reducing dead loads.
The project was a design/build awarded to PCL, in Issaquah, Washington. PCL hired Hardesty & Hanover, New York City, to provide engineering for the project. Hardesty & Hanover is the successor firm to Waddell & Harrington, and the firm was able to go back to original 1912 design documents for the bridge to help find cost effective solutions for project.
Prompted by funding concerns, David Evans and Associates developed a staged request for proposal (RFP) with a base program that addressed corrosion of the gusset plates and main chord as well as the bridge’s antiquated electrical system. The mechanical system, outdated but functional, was one of several supplemental packages. The winning team was able to perform the base program and all of the supplementals within the budget, which was bolstered by federal funds.
For a steel structure approaching 100 years old during the project, the team found the mechanical systems of the bridge in remarkably good condition, Shanafelt says.
“If we were not able to have replaced the mechanical equipment, it would have still operated and I think it would have operated well,” Shanafelt says. “The four main sheaves in the towers had to be rebuilt. The bearings were shot. There was a lot of friction. But they still operated.”
The bridge was a robust replacement for this earlier span, seen here
in 1903. Courtesy of Tacoma Public Library
The Hardesty & Hanover team designed an innovative solution that incorporates spherical roller bearings into the counterweight sheave assemblies. This allowed the team to reduce project costs and modifications to the structure.
Although gears and pulleys haven’t changed a great deal in 100 years, the electrical equipment was a different story.
“The electrical equipment was pretty scary,” Shanafelt says. “If you were in the machine room when the bridge went up, everything started to glow red. It was scary to be in there. Nothing met code. We were able through this RFP essentially to get our full program built. And so all the mechanical equipment is brand new. All the electrical equipment is brand new. We rebuilt the bottom cord. We in effect now have a duplicate bottom cord,” Shanafelt says.
The team installed a series of 2.5 in. thick high-tensile rods below the original bottom cord. These rods, two on each side, can carry 100 percent of the bridge load. And the rehabilitated bottom chord can also carry 100 percent of the load—a level of redundancy that Waddell would no doubt appreciate.
“PCL built a lot of the redundancy into the bridge,” Shanafelt says. “That was one of the reasons we picked the PCL team. It was a very robust design.”
Although the Murray Morgan Bridge has been a fixture of the Tacoma skyline for 100 years, and is an important example of an early lift span structure, the project is characterized as a rehabilitation, not a restoration.
The steel rods, for instance, are not historically accurate. And although they aren’t easily visible, no effort was made to conceal them. The project also included the addition of concrete safety barriers between traffic and pedestrian lanes.
Although the team didn’t have the budget to pursue a complete restoration of the bridge, engineers were sensitive to aesthetic issues to make the bridge appear as it did on its 1913 opening.
“We did emphasize historic features that we wanted to maintain so that the outward appearance of the bridge would stay the same,” Shanafelt says. “We went back and painted it the original black. We retained the pedestrian handrails. We wanted to maintain the appearance and its historic character.”
The rehabilitation of the Murray Morgan Bridge was a win/win solution for the city. Razing the bridge would have cost $26 million and left a hole in the city’s infrastructure. Replacing the bridge with a moveable span structure would have cost an estimated $105 million.
“The Murray Morgan Bridge is a symbol of the hard work and ingenuity that Tacoma is built on and just like 100 years ago, the Murray Morgan Bridge continues to serve as a vital link and foster economic development between downtown and the East Foss Peninsula,” said Mayor Marilyn Strickland in written comments to Civil Engineering online.