Minnesota and North Dakota Perform $16M Rehabilitation of Historic Kennedy Bridge
Partnering in the Name of Preservation: State Transportation Agencies Work Together to Restore Historic Kennedy Bridge at North Dakota-Minnesota Border
Built in 1963, the historic John F. Kennedy Memorial Bridge (Kennedy Bridge) serves as a vital east-west connector between the cities of East Grand Forks, Minnesota, and Grand Forks, North Dakota. In addition to ferrying U.S. Trunk Highway 2 traffic, it is also one of the area’s only Red River crossings designed with enough clearance to remain open during extreme flood events.
In March 2017, the Minnesota Department of Transportation (MnDOT), in partnership with the North Dakota Department of Transportation (NDDOT), spearheaded a $16 million rehabilitation project to maintain the long-term performance of the aging structure, which was deemed structurally deficient in 2013. The cooperative undertaking, which involved replacing the worn bridge deck as well as one of the structure’s three concrete piers, is expected to conclude this summer.
“This landmark piece of infrastructure, which carries about 20,000 vehicles per day, is integral to one of the highest-trafficked roadways in our district,” says Paul Konickson, MnDOT District 2 Bridge Engineer and Project Manager. By 2035, traffic demand in the area is expected to increase to about 30,000 vehicles per day. “Along with preserving the historic nature of the Kennedy Bridge, this rehabilitation project will improve safety for motorists, pedestrians, and bicyclists.”
A Bridge of Significance
The Kennedy Bridge, originally known as the Skidmore Avenue Bridge but renamed in honor of President John F. Kennedy, was designed by NDDOT’s award-winning Bridge Engineer Joseph Kirby and built by Giertsen Company. Spanning a major river subject to frequent flooding and subsoil movement, the 1,261-foot structure is situated within an urban setting along Gateway Drive, a key commercial corridor, and to the east of three historic properties located in North Dakota.
In addition to the significance of its location, the Kennedy Bridge is eligible for listing on the National Register of Historic Places due to its rare design. Specifically, it features two Parker camelback through-truss main spans flanked by 11 steel multi-beam approach spans. The 279-foot-long main spans are exceptionally long for a Parker truss structure, which typically has trusses ranging 40 to 250 feet.
Also, the bridge possesses additional engineering significance due to elements that accommodate the shifting clay soils of the Red River Valley, including a fixed central pier for stability, piers with rocker bearings at the ends of the truss sections, and pier bents supporting long approach spans. Despite these innovations, one of the support piers on the western side of the truss section of the bridge managed to slowly shift more than 2 feet toward the river – a dilemma requiring swift remedial action.
Rehabilitation vs. Replacement
Until recently, the Kennedy Bridge had experienced only minor alterations or repairs. But in the last decade MnDOT’s yearly inspection reports indicated that the concrete bridge deck was reaching the end of its useful life. Also, the structures existing steel girders and beams were designed for smaller vehicles, and failure of the paint has resulted in steel corrosion. What’s more, inspectors discovered soil movement had drastically decreased the capacity of pier 6, which supports the west end of the bridge.
According to an October 2015 rehabilitation report prepared by SRF Consulting Group, Inc. and Gemini Research, the waning structural integrity of pier 6 was chiefly responsible for the substructure’s overall poor rating under the National Bridge Inventory (NBI) scoring system. The pier suffered from severe cracking and a bow of approximately 5 1/2 inches in the concrete wall between pier columns, causing it to shift significantly toward the east and begin tilting.
MnDOT and NDDOT, in collaboration with local and regional planners, considered multiple plans of action to address potential structural failures, including a complete bridge replacement. Compared to the rehabilitation alternatives, building a new river crossing would have been more costly and had various adverse impacts to commuters and the surrounding communities.
Because the existing superstructure was found to be in satisfactory condition under NBI standards, the state DOTs opted to rehabilitate, repair or replace significantly deteriorating bridge components – including pier 6 and its foundation along with the entire bridge deck. This approach also allowed the current four-lane deck configuration to be modified to accommodate a pedestrian/bicycle shared-use path.
Restoring a Regional Landmark
The bulk of restoration work took place between 2017 and 2018, led by Wisconsin-based Zenith Tech, Inc. as the prime contractor. Other key members of the project team included SRF Consulting Group (bridge/roadway engineering design), Thomas Industrial Coatings (painting), Strata Corporation (concrete contractor), Braun Intertec (geotechnical engineer), Moorhead Electric (electrical contractor) and E&J Rebar Solutions (rebar contractor).
In March 2017, construction crews started off by jacking up the west side of the bridge several inches to build a temporary pier, then proceeded to demolish and replace the existing damaged pier 6. Konickson notes, “In conjunction with the pier replacement, a geotechnical monitoring system was installed in the substructure to observe what happens in the future in terms of pier or slope movement.”
The next phase involved replacing the bridge deck in two stages, starting with the south half of the deck in 2017 and then then north half in 2018. “Along with the bridge deck replacement and removal, crews also replaced the roadway pavement on the approaches leading up to the bridge,” Konickson adds.
Although each of the four driving lanes are now 11 1/2 inches (a decrease of 6 inches), the outside shoulders are now 4 feet, 3 inches wide (an increase of 15 inches) to enhance safety and provide wider areas for emergency stops.
Unlike the layout of the previous bridge deck, the new design does not include a center median, which allows space for a new 8-foot-9-inch protected pathway on the north side of the bridge that connects to the greenway trails running along both sides of the Red River.
Last year, workers performed blasting and painting and installed a new aesthetic lighting system on the bridge trusses. Final touch-up painting is scheduled to wrap up this month. Other minor work taking place this year includes grinding down the concrete roadway and bridge surface to provide a smoother ride for travelers, adding permanent pavement markings, removing temporary access roads, and final turf establishment.
In total, the bridge deck and its approaches required approximately 14,400 square yards of concrete (5,000 for new pavement and 9,400 for the bridge slab) along with 800,000 pounds of rebar for the bridge deck, pier and barrier. Workers constructed an additional 3,800 linear feet of concrete barrier on the bridge and also painted more than 183,000 square feet of structural steel.
Project Obstacles and Solutions
The project achieved substantial completion in December 2018, at which point all four traffic lanes were opened to commuters. Before this point, MnDOT generally maintained one lane of open traffic in each direction throughout the construction process, save for nine short-term bridge closures. When the Kennedy Bridge was closed for repairs, traffic had to be diverted to other nearby Red River crossings.
“There’s really only two other bridges in town, one that normally carries 7,000 vehicles per day and another that carries about 13,000 vehicles per day. So, basically, we doubled the traffic on those two bridges,” Konickson explains. “The cities worked with us very well, whether it was having local law enforcement help out with traffic control, or helping us devise better traffic control strategies during our weekly project meetings.”
Despite contending with heavier-than-usual congestion, the rural communities on both sides of the river were pretty patient and understanding, he adds. “This area has a major agricultural industry, specifically sugar beet farms, and also has a busy Crystal Sugar processing facility. We tried to accommodate these industry needs as best as we could, scheduling bridge shutdowns during non-peak periods,” Konickson says.
Konickson concludes, “As with any multi-year project, there were various challenges to completing the construction work across multiple seasons. Overall, everything turned out really well thanks to support from NDDOT as well as municipal leaders from both states.”
Photos courtesy of the Minnesota Department of Transportation