Rehabilitation is a major part of preservation. Rehabilitation keeps a historic bridge in active service, carrying vehicles, bicyclists, and pedestrians, while preserving Minnesota’s transportation heritage. It involves repair and upgrading of structural and mechanical components. Through periodic rehabilitation work, along with regular maintenance, a historic bridge can stay in active service for 100 years or more.
Historic bridge rehabilitation work must comply with federal requirements called the Secretary of the Interior’s Standards for the Treatment of Historic Properties—or the Secretary’s Standards. Compliance with the 10 Standards for Rehabilitation ensures that the bridge retains historic materials and appearance while meeting engineering and accessibility requirements.
Careful inspections, regular maintenance, and rehabilitation of Minnesota’s historic bridges is ongoing statewide. Below are several current and recent projects.
The planned rehabilitation for Bridge 2440, the Third Avenue Bridge over the Mississippi River in Minneapolis, includes removal and replacement of the deck, rehabilitation of the ornamental railing panels, and repair to piers, arch ribs, and barrel arches. When replaced, the railing will be elevated on a concrete curb to achieve the required height standard and current openings will be narrowed to code-required dimensions through the use of narrow bent bars. Spandrel columns will be removed and replaced with new spandrel cap beams closer to the original design. The character-defining Melan arches will receive extensive repairs along with proposed cathodic protection to reduce further chloride deterioration. The piers are also character-defining but badly deteriorated; therefore, piers 1 and 8 will be extensively reconstructed and remaining piers 2-7 will be repaired. North (east bank) abutment retaining walls will be partially reconstructed.
The planned rehabilitation project for Bridge 2796, which carries Tenth Avenue over the Mississippi River in Minneapolis, includes replacement of the deck, sidewalk, and railings on the arch spans. Traffic lanes will be reduced from four to two, with sidewalks on both sides instead of the one sidewalk currently on the bridge. New concrete railings and light standards will be detailed similar to the original construction.
Deteriorated spandrel columns and caps beneath existing deck joints will be replaced and the number of expansion joints will be reduced in the new deck. An innovative post-tensioning technique termed the “YOWMen System” will be installed in the deck and piers. A thermal spray coating (TSC) to reduce further concrete deterioration will be sprayed on the tops of the Melan arches. All existing utilities will be removed and only two gas mains will be replaced.
The project is expected to begin in late 2019.
Wabasha County used funding from a Minnesota Historical & Cultural Heritage Grant (Legacy Grant) to develop rehabilitation plans for this 1937 multi-plate arch bridge that carries County Road 68 over a tributary of the Zumbro River. The project will include a complete repointing for the headwalls, railing, piers, and abutments, with replacement of deteriorated or missing stones. The concrete arch ring, formed to replicate a stone arch ring, will be repaired, along with deteriorated concrete in the piers and abutments. Fill over the arches will be excavated to apply a waterproofing coating to the multi-plate surface and the drainage system will be rehabilitated to assure proper functioning. Rusting arch surfaces will be cleaned and coated to slow corrosion.
Bridge 3355, the Whitefish Creek Bridge, carries U.S. Highway 169 over White Fish Creek, where it enters Lake Mille Lacs in Mille Lacs County. The bridge will undergo rehabilitation beginning in 2019. Historic stone masonry will be repaired and repointed, including bridge abutments, walks, and the guardrail stone wall. The bridge deck and approach lanes will be reconstructed and an integral Wyoming-type guardrail will be installed.
The proposed rehabilitation of the 1924 (widened in 1939) Stewart River Bridge (Bridge 3589), which carries Trunk Highway 61 over the Stewart River north of Two Harbors, will involve the construction of a nearby parallel bridge to create a one-way pair. With completion of the new bridge, rehabilitation will begin on the historic bridge. The work is anticipated to include repairs to the concrete arch and wingwalls and a reconfiguration of the roadway and sidewalks, with consideration given to rehabilitation of the historic railing.
The Split Rock Bridge (Bridge 5744) is a true stone-arch structure, built by the Works Progress Administration (WPA) in 1938, carrying County Road 54 over Split Rock Creek near Ihlen in Pipestone County. Rehabilitation plans were prepared with funding from a Minnesota Historical & Cultural Heritage Grant (Legacy Grant). The roadway and fill will be removed above the stone arch and all stone masonry on the interior and exterior will be repointed. The upper surface of the arch will be protected by waterproofing before the fill is replaced. Deteriorated sections of the railings and upper wing walls will be reconstructed using replacement stones where necessary from the Jasper Quarry located four miles south of the bridge, which is the source of the original stone for the bridge. All work will comply with the Secretary of the Interior’s Standards for Rehabilitation.
Whitewater Culverts (Bridge 8592, Bridge 8593, Bridge 8594, and Bridge 8595)
The four culverts are in fair to poor condition and a basic rehabilitation is planned for each one. Included will be a selective replacement of cracked and unsound stones, reconstruction of severely deteriorated sections, and repointing overall. The existing stone floors will be repointed or reconstructed and a new protective concrete overlay will replace the existing overlay to protect against scour and erosion from the high-velocity water. Geo-grid soil reinforcement will be installed where needed for slope reinforcement. Flume walls will be repaired or reconstructed and also extended where necessary. The I-beams added to the metal multi-plate arch in Bridge 8593 will be removed and corroded partial plate sections will be replaced.
Using funding from a Minnesota Historical & Cultural Heritage Grant (Legacy Grant), Waterford Township has prepared plans for the rehabilitation of Bridge L3275, a historic Camelback through truss crossing the Cannon River near Northfield in Dakota County. The planned project, designed to comply with the Secretary of the Interior’s Standards for Rehabilitation, will reconstruct elements of the concrete abutments and remove and reconstruct the concrete deck. Existing bearings will be replaced with modern bearings. Selected gusset plates will be modified with steel plates and the existing railings will be replaced with new code-compliant railings. The trusses and floor system will be blasted and repainted and the one existing historic bridge plaque will be refurbished and replicated to replace the second and missing plaque.
Using funding from a Minnesota Historical & Cultural Heritage Grant (Legacy Grant), the City of Beaver Creek, Rock County, has prepared plans for the rehabilitation of the historic Bridge L4646, constructed in 1911 to carry Sixth Street over Spring Brook. Perley N. Gillham, a local bridge builder, designed this important early reinforced-concrete bridge. The planned rehabilitation will repair all deteriorated elements of the existing concrete, including spalled surfaces, cracks, and delaminated areas. The existing gravel road surface will be removed to expose the top of the concrete arch for repair and waterproofing. All work will be completed in compliance with the Secretary of the Interior’s Standards for Rehabilitation.
The planned rehabilitation project for Bridge L5391, the Third Street Bridge in Cannon Falls, will include repairs to components of the steel trusses and to elements of the floor system. The existing truss bearings will be replaced with new elastomeric bearing pads. Deteriorated and missing railing endposts will be replaced with cast replicas. The existing timber bridge deck will be replaced with a new concrete deck. The backwalls of the existing concrete abutments will be removed and replaced to facilitate expansion and contraction and the abutments will be protected with limestone riprap to prevent undermining and future movement. The rehabilitated trusses will be repainted in a historically appropriate neutral gray. The rare existing name and date plaques above each portal will be cleaned and preserve
Repairs to extend the service life of Bridge L7075 included removing fill over the multi-plate arch to allow repairs to the metal arches. New, protective, structural concrete infill was placed over the arch and waterproofed. The concrete is below the headwalls and beneath the new bituminous driving surface so it is not visible. Missing stones in the masonry were replaced and all exterior masonry surfaces were repointed. The project was completed in 2016 using Town Bridge Funds.
Currently in process
On August 2, 2017, MnDOT redirected all vehicular traffic from the historic Stillwater Lift Bridge to the nearby new St. Croix Crossing bridge. The Stillwater Lift Bridge’s closure formally ended its 86-year-life as a major vehicular transportation crossing of the St. Croix River. The subsequent two-year rehabilitation project has converted the bridge to pedestrian and bicycle service on a new trail system. Still subject to federal navigation regulations, the lift span continues to operate on an official schedule.
The conversion project included a significant rehabilitation of all parts of the bridge, including the mechanical lift machinery and upgrades to the system’s electronics. Necessary repairs were made to the bridge tender’s house and some structural members. Railings and sidewalks were reconfigured to meet requirements of the Americans with Disabilities Act (ADA). Historic lights and the concrete balustrade were restored and the entire bridge was repainted in its original green color. A significant feature, the approach concourse on the downtown Stillwater end, was reconstructed to bring back its original surface configuration. All rehabilitation and repair work was completed in compliance with the Secretary of the Interior’s Standards for the Rehabilitation of Historic Properties.
In the last 20 years, Minnesota bridge owners have rehabilitated more than 40 historic bridges. Below are several recently completed examples.
Completed in 2019
Bridge 5265, the Garrison Pedestrian Underpass, was built in 1938 by the Civilian Conservation Corps as part of an extensive wayside development project in the vicinity of Mille Lacs Lake, Crow Wing County. It is an Armco multi-plate corrugated-steel arch with stone masonry headwalls. As part of the rehabilitation project, completed in 2019, the deteriorated metal multi-plate arch was repaired and reinforced with replacement steel and the stone masonry was repaired and restored. A new concrete bridge deck was added.
The 1942 Winona Bridge (Bridge 5900) completed a full rehabilitation in 2019. To accommodate increased traffic between Minnesota and Wisconsin, a second and parallel Mississippi River bridge was first built just upstream in 2016. At that point, all traffic was temporarily shifted to the new bridge and the historic bridge was closed for rehabilitation. Both bridges are now open to traffic as a one-way pair.
The three, steel, cantilevered, through-truss spans across the river—the bridge’s most significant feature—received extensive steel repairs, completed in compliance with the Secretary of the Interior’s Standards. Truss members also were retrofitted for internal redundancy as a state-required safety measure. These main spans retain all historic features and character.
The steel deck-truss approach spans on each end of the through trusses, also significant features, were removed and replaced with replica trusses using modern steel materials and construction techniques. The concrete approach spans on the south or downtown Winona side of the river were replaced with new prestressed-concrete spans in a modern design reflecting the materials and character of the original spans. At each end, the abutments of the historic and the new bridges are situated side-by-side in a complimentary arrangement, with original historic features replicated in the reconstructed abutments.
Videos of the Winona Bridge (Bridge 5900).
The Boom Island Bridge (Bridge 93835) was originally built in 1901 by the Wisconsin Central Railway Company to provide rail access from Nicollet Island across the Mississippi River channel to its new railroad yard on Boom Island. The Pratt through-truss was designed by Charles F. Loweth, an important Minnesota bridge engineer. The rail yard and buildings were removed around 1970 and the area was converted into today’s park. The bridge was converted from rail to bicycle and pedestrian use.
In 2018-2019 the bridge was rehabilitated. The existing timber deck was removed and steel repairs were completed to deteriorated parts of the floor support system. A new wood plank deck was installed. When in service as a railroad bridge, there was no railing. The chain-link fence added for pedestrian use was replaced with a new metal tube and cable railing with safe narrow openings. Concrete abutments were repaired. The entire bridge was cleaned of deteriorated old paint and repainted and sealed to minimize the development of pack rust.
Completed in 2018
The Broadway Bridge (Bridge 4930) carries State Highway 99 over the Minnesota River at Saint Peter in Nicollet County. This two-span, steel, through truss bridge was completed in 1931. To accommodate river currents, the center pier between the two Pennsylvania-type truss spans was designed at an angle, or skewed, in relation to the bridge ends at the abutments. That skewed pier alignment required an unusual arrangement of trusses on the upstream and downstream sides of the bridge, contributing to the structure’s historic significance.
During the rehabilitation in 2017-2018, the steel trusses were repaired and repainted in the historic color of dark green. The concrete abutments and approaches were repaired and reconstructed with surfaces carefully finished to match the original concrete. The truss floor beams and other members were strengthened to accommodate current vehicular loads and a new concrete deck was poured. The historic lights on the bridge and approaches were refurbished and replicated where necessary. An extended concrete embankment wall was erected in front of the west abutment to protect the foundation from erosion by the river, which changes depth constantly and is subject to seasonal flooding.
The rehabilitation project for Bridge 9090, the Kennedy Memorial Bridge that carries U.S. Highway 2 over the Red River of the North at East Grand Forks, was completed in 2018. One of its three river piers was replaced with a similar pier that is one foot wider to facilitate future jacking of the west truss for repairs or resetting bearings. A new replacement concrete deck now includes a pedestrian-bike path separated from vehicles with a concrete barrier. The bridge railing was reconstructed with the original aluminum posts and rails, but mounted on a higher concrete parapet to meet modern safety standards. The truss floor beams were strengthened, the truss bearings were replaced, and a pin-and-hanger system that allows the bridge to move was replaced. After minor repairs, the large trusses were repainted in the original metallic color.
Bridge 9395 is a three-span, continuous, steel-girder structure. It carries State Highway 61 over the deep gorge of the Beaver River in the municipality of Beaver Bay, along Lake Superior’s north shore, in Lake County. It is significant as Minnesota’s first major highway bridge with welded girders. Standard practice before this was to “roll” hot, malleable steel into a girder or to rivet together steel plates and angles to “build up” a girder. Welding reduced the size and weight of girders, lowered fabrication time and cost, and decreased maintenance requirements. Bridge 9395 was built in two stages, one side in 1958 and the other in 1959, and was essentially two mirror-image structures separated lengthwise by a 1-inch gap. While sharing abutments and piers, these superstructures were not physically linked but effectively functioned as a single structure.
In 2017-2018, MnDOT rehabilitated Bridge 9395 to address deterioration of the deck and girders. The deck’s condition was so poor that it had to be completely replaced. This was an opportunity for MnDOT bridge engineers to consider reconfiguring the deck in light of today’s design standards and to accommodate a request by the Minnesota Department of Natural Resources for a pedestrian/bicycle lane for the new Gitchi-Gami State Trail. The engineers eliminated the 1-inch center gap and made the deck continuous, incorporating a protected 12-foot lane for the trail on the northwest side.
The original deck was flanked by concrete barriers topped by two-pipe aluminum railings. The barriers did not meet current safety requirements, but the aluminum railings were an important aspect of the bridge’s visual character. The contractor carefully removed the aluminum railings and kept them in a secure location while completing work on the new deck. MnDOT’s bridge engineers reviewed modern crash-tested barriers and selected the TL-4 design (known as the Nebraska Department of Roads Concrete Bridge Rail) as the closest in appearance to the historic barriers. These were installed on the new deck and the aluminum railings were mounted on top. The original bronze bridge plaques were attached to the new concrete end posts.
Beneath the deck, the original wind bracing was producing fatigue cracks in the girders. To stop the damage but retain this historic feature, splice plates with slotted holes were added to the bracing to allow movement. While the original design had too much wind bracing, the lateral bracing was insufficient, and six rows of new diaphragms had to be installed. Angle stiffeners for the diaphragms were bolted to the girders with hex-head bolts to differentiate them from original girder splice plates, which were riveted in place. All of these elements and the girders received fresh paint, which matched the historic color as closely as possible.
Completed in 2016
Through local efforts, the Dodd Ford Bridge, erected in 1901 in rural Blue Earth County near Amboy, was rehabilitated and reopened to traffic in 2016. The single-span steel Pratt-type truss is important as an example of the work of Lawrence Henry Johnson, an important early Minnesota bridge engineer.
The truss span was lifted off the deteriorated original abutments and placed on temporary supports while the contractor built new abutments. Then new steel I-beams were installed to span the Blue Earth River and support the historic truss, helping carry modern traffic loads, while maintaining the bridge’s historic character.
The rehabilitation resulted from a significant campaign my Blue Earth County citizens to promote preservation. In 2010, the Amboy Area Community Club received a Minnesota Historical & Cultural Grant (also known as a Legacy Grant) to assist in hiring a consultant to examine the costs and methods needed to restore and preserve the bridge
Constructed in 1920, the bridge was designed to span Long Meadow Lake, an overflow area of the Minnesota River just beyond the main river channel. It is significant for its five, steel, riveted, Camelback-type through-truss spans. The bridge had been closed to vehicular traffic since 1993 and closed to pedestrians in 2002. Its historic status required consideration of rehabilitation when the need for a trail crossing was identified at this location.
Beginning in 2015, the rehabilitation restored the bridge for pedestrian and bicycle use. Using an adjacent, temporary support system, the trusses were lifted off the piers and abutments so steel members could be repaired and restored to their historic appearance Truss members bent by previous vehicle collisions were heat-straightened. The timber deck was replaced with a concrete deck. New code-compliant railings were installed. Concrete abutments and piers were repaired. Graffiti was removed and steel was repainted. The rehabilitation work was completed in 2016.
Completed in 2015
Built in 1904 to allow pedestrians to cross over the streetcar track at the adjacent station, the Como Park Pedestrian Bridge is one of the oldest reinforced-concrete bridges in Minnesota. It was designed by noted Minneapolis bridge builder, William S. Hewett, and incorporates the patented Melan arch steel reinforcing system.
Before rehabilitation, the bridge had seriously deteriorated. The pedestrian railings had crumbled, forcing the city to close the bridge and the trail below, which had replaced the original streetcar track. Concrete on the arches had also deteriorated, exposing the internal Melan steel system. The federally funded rehabilitation project included removing unsound concrete, forming new concrete to restore the shape and details of the original bridge, placing a waterproof membrane below the deck to protect the arch from water damage, installing of a new deck that recreates the scoring pattern of the original deck, and custom-made decorative railing to match the original.
The restored bridge now provides a sound pedestrian crossing above and trail amenity below, and returns one of the iconic early twentieth century features of Como Park. The work was completed in 2015.
Completed in 2014
Built in 1933-1934, the Roosevelt Bridge in Austin, Minnesota, is significant for its unusual construction and as a representative of a Depression-era federal program. It was built with funding from the Civil Works Administration (CWA), one of the earliest New Deal programs and one of the briefest, lasting less than six months. The bridge carries Fourth Street Southeast (formerly River Street) over the Cedar River and is unusual in having stone masonry foundations supporting reinforced-concrete arches.
During the 2011-2014 rehabilitation, deteriorated stone masonry was replaced by stones matching the original size, color, and texture in areas of the abutments, pier, arch ring stones, spandrel wall, railing, and stringcourse. The replacement stone replicated the unusual undulating coursing pattern created by the original stone masons in the 1930s.
The rough-faced, random-coursed limestone railing was replaced with a new rail with a crash-tested reinforced concrete core and stone veneer. Bridge lights and pilasters were reconstructed using historical photographs and drawings as a reference.
In 2016, the American Council of Engineering Companies of Minnesota (ACEC/MN) recognized the rehabilitation of the Roosevelt Bridge with the Grand Award for Excellence in Engineering. The project was also recognized by the Preservation Alliance of Minnesota with an Honor Award in 2015.