Ames Construction Replaces I-35W Minnesota River Bridge and Approach Roads to Manage Flooding
A Team Effort: Ames Construction and Minnesota DOT Replace the I-35W Bridge with Help from Various City and County Organizations
Faced with an aging bridge, the Minnesota Department of Transportation (MnDOT) decided to replace the heavily traveled Interstate 35W Minnesota River Bridge and approach roads.
“The two new bridges will allow for added motor vehicle and pedestrian/bike traffic capacity,” says Alex Carlin, Senior Project Manager with Ames Construction of Burnsville, Minnesota, the design-build prime contractor. “In addition, when the project is done, I-35W mainline approaches will be lifted out of the flood zone.”
I-35W runs north and south across the Minnesota River between Bloomington and Burnsville, south of Minneapolis. The bridge was built in the 1950s and carries about 140,000 vehicles per day. The river rises and falls frequently.
“The approach on the south side is in a floodplain and prone to flooding,” agrees Tom Villar, Construction Manager with MnDOT.
MnDOT joined with Dakota County, Hennepin County, the City of Bloomington and the City of Burnsville to replace the bridge and pavement. The project aims to improve safety, enhance mobility, upgrade drainage, and create a smooth road surface.
“This project is going extremely well,” Villar says. The department opted for a design-build delivery system.
“It gives the designer and contractor some flexibility in how to keep that traffic going through during construction,” Villar says. “We have to keep six lanes of traffic flowing, three lanes northbound and three southbound, and that has been a challenge. The only times there have been closures are at nighttime.”
Scope of Work
In addition to replacing the 1,362-foot-long Minnesota River Bridge, the project included reconstructing the bridge spanning 106th Street, replacing pavement and widening nearly one mile of the road from Cliff Road to 106th Street, and constructing a northbound auxiliary truck lane, to give trucks a place to climb more safely. The contract also includes a pedestrian and bicycle shared-use trail, and improvements to signage, lighting, and drainage.
“It’s about a 50-50 split between the bridge work and roadway work,” Villar says.
Ames Construction received the $127 million design-build contract. The company was founded in 1962 and remains a family-owned business.
Parsons Transportation in Minneapolis was the bridge designer, and Alliant Engineering, also of Minneapolis, was the road designer.
Crews began working in August 2018, with completion scheduled for fall 2021. Ames has been working double shifts, six days per week and continued working through the winter.
All traffic remained on the existing bridge, while Ames constructed the northbound bridge off line. The northbound bridge includes a 12-foot pedestrian trail, which the contractor used for temporary traffic when the new northbound opened in fall of 2019.
“There was some ingenuity on the team’s part to use that future pedestrian trail for traffic,” Villar said.
Many Types of Equipment
The new bridge is a conventional five-span steel-girder structure, Villar said. The center main span is 385 feet long over the river. The foundations for the river piers, two northbound and two southbound, are constructed using 42-inch pipe pilings in the river, which required a marine operation. The piles reach to 120 feet, and Ames used a DELMAG D-125-32 Pile Hammer to place them.
Additional equipment used during the extensive marine operation were two Terex American HC230 Cranes, a Manitowoc MLC 165 Crane, two Manitowoc 1100-1 Cranes, a Manitowoc 222 Crane, a Grove RT600E Crane, a tug boat, two crane barges, one material barge, and multiple sectional barges.
“The big challenge was working in the flood plain on the river,” Villar says. “We had 22 feet of elevation change on the river, with extended periods of high water.”
River operations were completely shut down for six weeks and then another six weeks of limited operations. “The contractor dealt with that quite well,” Villar says.
Ames managed the rising and falling river levels by building access roads and pads to accommodate work during minor flood events.
“We perform the majority of the bridge substructure work within the river and flood-risk area during historical low-water times of the year, which is typically during the winter,” Carlin says. “Most of the superstructure can be built during high-water levels off of access pads and barges. With an all-out major flood event, all we can do is get out of the way and wait for it to recede, which is what happened spring and early summer of 2019.”
During the marine operations, MnDOT monitored turbidity, sent any discharge into sediment ponds, and environmental watchers weekly assessed the site for sediment control or discharge.
“The north approach widening area is very sensitive from a geotechnical standpoint,” Carlin says. “There was a substantial embankment failure during the original bridge construction.”
Ames analyzed that failure, and took this information into consideration for the new bridge.
“We had to install wick drains and place the embankment in well-defined staged lifts with settlement periods,” Carlin explains. “Extensive geotechnical monitoring was performed throughout the process to ensure the soils were acting as predicted in our design. This part of the construction process was completed early in 2019 and was very successful.”
Crews tore down the old bridge, once the new northbound bridge was completed and opened to traffic. It is carrying both north- and southbound traffic as the rest of the bridge is built. Ames removed the portion over land using jackhammer attachments on excavators and hauled it away. Over the water and wetlands, crews cut up the bridge and removed it piece by piece. Beams were taken out with a crane.
“The demo was reversed engineered,” Villar recalls. “They peeled the deck off and took the beams off, the opposite of how they were placed in the ’50s, and it went really well.”
The project has required 800,000 cubic yards of grading, 26,000 linear feet of storm-sewer pipe, 5 million pounds of reinforcing steel, 34,000 linear feet of foundation pile, and 14 million pounds of structural steel. The project remains on schedule and within budget.
Ames crews are currently building the southbound bridge.
“We’re teaming with Ames and the subcontractors,” Villar says. “There has been a lot of partnering, and it has gone well.”