Drivers, walkers and bicyclists will have one fewer way to cross the Mississippi River into downtown come March. That’s when the 10th Avenue Bridge will close for repair and reconstruction. When the work is complete 18 months later, pedestrians and bicyclists will have more room and drivers will be restricted to one lane each way.
The bridge, which is on the National Register of Historic Places, is made of reinforced concrete and is considered a fine example of bridge construction from the early days of automobile use. It was opened in 1929. It carries about 10,000 vehicles and 2,000 pedestrians and bicyclists per day, according to the City of Minneapolis.
Over the years, water has infiltrated the joints and seams of the bridge, weakening it and rusting the rebar that forms its skeleton. Some of the support columns and arches have cracks in them, and the rebar is showing. The project will repair not only the bridge deck, which was replaced in the 1970s, but also the bridge’s piers, arches and spandrels. Concrete removal has begun on some of the piers.
Once the bridge supports are finished, the deck will be re-laid and reconfigured. Plans call for a 10-ft.-wide sidewalk on the upstream side of the bridge (as you face downtown), and a pair of 6.5-ft.-wide bicycle lanes, one in each direction, next to it. The bike lanes will be protected from vehicle traffic by a 2-ft.-wide, 6-inch curb. Cars and trucks will travel to and from downtown in single lanes, one in each direction. The lanes will be standard 11-ft. lanes with three feet of clearance on the outside of each lane. A 12-ft.-wide sidewalk will line the downriver side of the bridge.
Perhaps the most interesting aspect of the project is the removal and relocation of a 5-ft.-wide water main on the underside of the bridge. The main, which carries fresh drinking water from the Minneapolis Water Treatment plant, has been attached to the bridge for 70 years. A new water main will be built under the river. A 70-ft.-deep shaft will be drilled on the east bank of the river, then a tunnel will be bored through the St. Peter sandstone layer beneath the river bed. The tunnel will connect with a 130-ft.-deep shaft on the downtown side, and water will be piped through it. The tunnel is not expected to affect the integrity of the bridge.
The price tag for the entire project is $60 million. The bridge is expected to reopen the summer of 2021.
Below: Views of the bridge show the deterioriation, and (middle) work underway on one of the piers. (Photos by Mark Peterson)