Dresbach Bridge Project - 2013 year in review
Significant progress has been made on the Dresbach Bridge in 2013, after construction began in late 2012. Since then, important milestones have been reached, and the project has earned accolades. The Dresbach Bridge was named one of the top 10 bridges of 2013 by Roads and Bridges magazine. Each year the magazine’s editorial staff recognizes the top projects in North America based on project challenges, impact to the region, and scope of work. The Dresbach Bridge project was selected in part because of the eco-conscious construction methods being used.
Crews constructed substructures for the eastbound river crossing (the piers in the river)
To begin building the piers, “cofferdams” were installed (cofferdams are temporary watertight enclosures). To build the cofferdams, crews first installed the sheeting (the metal exterior that forms the walls of the enclosure). Then, a pile driver was used to drive piles into the soil to provide support for the structure (the base of the pier). Next, crews poured a thick concrete seal that keeps water from pushing up through the bottom. Then, the water was pumped out of the cofferdam to expose the bottom and allow for further construction. After that, crews added a “footing” to support the pier pedestal—and from there, additional concrete will be poured to form the pedestal. Finally, the cast-in-place concrete box girder bridge will be constructed on top of the completed piers.
Segments of the permanent eastbound Interstate 90 pavement and part of the ramp leading into La Crescent from eastbound I-90 on the Minnesota side of the river were built
First, crews reconstructed the pavement structure (the sub-cut) and removed the old material. Then sand was brought in, and crushed rock was layered on top. Finally, the road was paved with concrete, which forms the final permanent pavement. Blacktop was used to tie in the new pavement with the existing pavement.
Pieces of five of the retaining walls have been built, and guardrails were installed on the retaining walls on eastbound I-90
The retaining walls will be stained with a coloring that is applied directly to the concrete. A tan/brown color was chosen to match the natural color of the bluffs.
Next year, reinforced soil slopes, which are a combination retaining wall and natural slope, will be created. By layering geotextile material with sand, crews will be able to make a steeper slope than would normally be possible. After that, topsoil will be added to the finished slopes and grass seed will be applied.
Some of the sand used behind the retaining walls was sourced from nearby Dakota Island. The general contractor for the project, Ames Construction Inc., partnered with the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service to utilize existing sand that had accumulated from channel maintenance dredging operations. Other sand used in the project came from a pit by Trempealeau, WI. and from a U.S. Army Corps of Engineers storage site in Brownsville, MN.
This photo shows abutments for the new bridge into the rest area:
Two rock catchment walls have been completed
Located adjacent to the new eastbound roadway, these rock catchment walls provide protection from rocks and boulders that fall from the bluffs. A footing is first installed to support the wall and then the wall is constructed on top of the footing. The walls are reinforced with rebar to help withstand falling rocks and boulders.
Over the winter MnDOT plans to complete most of the piers for the eastbound bridge, and then in spring will begin working on building the cast-in-place box girder bridge between the piers (the actual structural part of the bridge).
Other areas of focus for 2014 include:
- Working on the four land-side bridges—the bridges that go over the railroad tracks, and one fly-under bridge that goes from westbound I-90 to southbound Hwy 61—in addition to the river bridges
- Continuing work on the retaining walls
- Constructing westbound pavements from the north end of the project toward the bridges
- Continuing work on the Wisconsin approach area (east)
- Installing fiber optic cables to control the two dynamic message signs that will be installed along eastbound I-90 and northbound Hwy 61