By Katie Erdman
When the new 35W bridge is completed, visitors may want to take a walk underneath it instead of a drive over the top in order to get a look at a local connection to the project.
Hancock Concrete produced a precast concrete box culvert to serve as a walkway running parallel to the river and passing directly under the new freeway.
Hancock Concrete's Cannon Falls plant was subcontracted to produce 63 sections of box concrete for the walkway. The Hancock facility produced the end wing wall sections for one end of the structure and the other end will have a cast in place as a retaining wall.
The Minnesota Department of Transportation inspectors have visited the Cannon Falls plant. Gary Schmidgall, plant general manager, said that he felt all aspects of the project would be under close scrutiny, but that he was confident about the product.
The 63 sections built in Cannon Falls are 20 feet wide and 11 feet high, making the 35W project the largest precast box culvert built in Minnesota.
The side walls of each section are 14 inches thick and the top and bottom walls are 15 inches thick. The reinforcing steel required is also greater than any previous box Hancock has made. The sections were made in 4-foot lengths and each section weighs 50,000 pounds. Delivery of the 63 pieces began on April 22. Because of the size and weight of the box culverts, each 4-foot section was hauled laying down on a trailer. The Cannon Falls plant began building the sections March 19 and four of the sections were produced each day. The last section was finished on April 11.
In Hancock, crews worked on wing wall end pieces that would go on the east end of the walkway. The pieces will create a 24-foot wing wall that is sloped to match the embankment fill.
Hancock Concrete's truck drivers from Hancock and Cannon Falls spent several days delivering the sections to the site. The assembly of the tunnel began as the pieces were delivered and fitted together in a tongue-and-groove fashion. The tunnel will run parallel to the river under the 10-lane interstate near Washington Avenue.
The tunnel is designed to stand up under the weight of traffic and 15 feet of soil placed over it. The completed tunnel will be 252 feet long and is designed for walking, in-line skating and biking. The tunnel will belong to the City of Minneapolis and may not be open for a year or two since the city must paint, light, pave, and provide other amenities before it can be used. The tunnel would not have been built if the road had not been dug up.
Hancock subcontracted the work from Flatiron Constructors, Inc./Manson Construction, the general contractor on the bridge. The new 35W bridge will cost about $234 million and is to be completed in 437 days from start of construction.