Rising waters and swift currents halted construction on a new, $120 million bridge over the Mississippi River that will feature the longest free standing arch main span in North America. At a river crossing richly embedded in Minnesota’s transportation history, bridge crews from the joint venture of Lunda-Ames Construction dropped their tools and moved their heavy equipment to higher ground late last month to wait out the high water.
Located in Hastings, Minn., just 20 mi. (32 km) south of St. Paul, the new bridge will be 2,000 ft. (610 m) long with a road width of 90 ft. (27 m) to carry four, 12 ft. (4 m) traffic lanes and a 12 ft. (4 m) pedestrian and bike path on its east side.
Minnesota Department of Transportation officials see this new bridge as another historic landmark for this site to continue a tradition of unique and iconic bridges established by the first bridge here which incorporated a spiral road deck at its south end. Unique in its design and the only known bridge of its type in this country, the Spiral Bridge is said to be one of only two of its kind in the world at that time, according to MnDOT staff.
The joint venture of Lunda-Ames Construction has more than 100 years of heavy construction experience between them. Lunda Construction is headquartered in Black River Falls, Wis., while Ames is based out of Burnsville, Minn. Both companies have regional offices around the country.
Though the flood set construction back several weeks this season, the overall schedule is not in jeopardy, said Steve Kordoksy, and Hastings Bridge project manager of MnDOT.
However, if a predicted second crest occurs, depending on the timing of this crest, there could be an impact on this year’s schedule, Kordoksy added.
This bridge crossing carries TH 61 traffic, a north/south highway that hugs the Mississippi River from IS 90 cutting across southern Minnesota into St. Paul. It also brings commuter traffic directly into Hastings, a historic frontier river town of about 21,000 residents that sits directly on the west bank of the river.
Due to a higher than normal and close to record snow accumulation throughout Minnesota, project engineers listened closely to flood forecasts that began to filter out from the National Weather Service in late January.
As spring approached and the temperatures finally began rising, bridge crews began preparing for an expected flood crest for late March, Kordoksy said.
“Part of your preparation is deciding what work you’re going to do and what work you’re not going to do given the flood forecast we had in early March,” Kordoksy explained.
Future work on pier six, which has its cofferdam in place and sits near the center of the new bridge, was directly affected by this planning and preparation process.
“For pier six we decided in the beginning of March to not do the excavation and not drive the piling because we didn’t think we could get the work done before the flood and we did not want to start it unless we could finish it,” Kordoksly said. “It was a risk factor the contractor weighed.”
At the same time, the contractor focused on portions of the piers that they could get done and on some precautionary measures.
“Rip rap was placed around pier six and because there was some scour history on two of the piers of the existing bridge the contractor placed rip rap around them as well,” Kordoksy said. “What we knew is that we had a pretty significant flood coming and given the contractor was going to be out there placing rip rap anyway, it just seemed to make good engineering sense.
“The contractor has taken some of his equipment and flotilla of barges holding cranes to a marina just on the other side of the project and spudded them down in the cove out of the main stream of the current,” Kordoksy added.
Rising waters also forced crews to move construction trailers, material, cranes and other equipment to higher ground from a staging area and barge access just upriver from the project.
Among the equipment on site moved to higher ground and to the marina included Cat backhoes and several Terex and Manitowoc cranes. Included in this mix is a Terex 210 ton (189 t), a Terex 175 ton (158 t), a Terex 50 ton (45 t) and a Manitowoc 222 ton (200 t) crane.
Though the four piers north of pier six are under various stages of construction and under water, none of them — including pier six — will be damaged by the flood.
Minor damage is expected, though to a temporary causeway shooting out from the east bank of the river that serves as a work platform for equipment and workers.
“I suspect that there will be some minor re-work needed on the causeway, maybe pouring additional rock that may have been flushed away will have to be added to get it back up to its elevation prior to the flood,” Kordoksy said.
Like farmers, Lunda and Ames bridge crews are now at the mercy of the whims of the Minnesota climate. Because the contractor blocked out several weeks as lay down time for possible spring flooding as part of the bid, work could remain on schedule for this season.
However, “if this flood persists into May, we could be looking at some time impacts,” Kordoksy said. “Right now the work out on pier six is critical. The schedule shows that work there will begin May 2. If the water is still high, there could be cause to have the completion date slip forward.”
When bridge crews return back to the site, they will continue to labor for another two years to build a steel girder, post-tensioned pre-cast tie girder bridge with the pair of visually stunning arches that will loom above traffic, pedestrians and boaters on the river below. When completed in late 2013, it will usher in a second century of bridge transportation for commuters and Hastings residents.
And like the first bridge completed there in 1895 at a cost of $39,000 and what would become known in Minnesota’s history as the “Spiral Bridge” it will be a structure that is set to be another historic landmark for this river crossing and noteworthy for its visual impact, according to MnDOT officials.
To build the first bridge at a standard height to keep the river channel below open to navigation and bring bridge traffic, originally horse and carriage, from one side of the river to the other directly into the developing city center led the designer of the first bridge to “think out of the box” and come up with a creative solution.
Replacing a late 19th century rope ferry, the designer drew in a spiral road deck on the south end of steel truss structure to bring traffic directly into the growing downtown business and entertainment center. Without the spiral road at its south end, a bridge of standard design would have overshot the town’s entrance located directly on the west bank of the Mississippi River and bring traffic over and away from its growing downtown district, according to historical documents.
The Spiral Bridge ushered in 20th century vehicular traffic and survived for over 50 years despite being designed originally to carry much lighter traffic. However, the bridge that became ingrained in Minnesota history and a structure that became a destination in itself, began to show signs of wear.
Despite efforts to save the bridge, engineers were forced to declare the Spiral Bridge to be unsafe for heavier traffic. Crews demolished it in 1951.
Though the state was not able to preserve the original structure, a detailed replica, built to scale using the same materials, now sits on a farm south of Hastings.
Though the second and current steel truss bridge is safe, it is functionally obsolete. The roadway is not wide enough and the clearance does not meet current standards, according to the project web site.
An accelerated funding schedule passed by the Minnesota Legislature allowed the construction of the new bridge, originally set for 2015, to be moved up on the replacement schedule.
The history of the Spiral Bridge and the above deck steel support system of its replacement, the historical nature of the town and the significance of visual aesthetics played heavily into coming up with the new bridge design, during the environmental review and design process, Kordoksy noted.
“There’s a connection here between the community and the bridge. It’s part of the national park system and the fact that the other two bridges had above deck structural elements, MnDOT decided to build a bridge with above deck structural elements,” Kordoksy explained.
Though admittedly the cost for this structure will be higher than the traditional concrete girder bridge, “it is important to note that the bids for this project came in considerably lower than what we had anticipated,” Kordoksy said.
To date, much has been accomplished during the late fall and winter construction season marked by a pattern of huge snow falls and cold weather that started in the middle of November and hung in until the middle of March.
Most of the work completed to date is bridge substructure work and retaining wall foundations. Shafts have been drilled and footings poured for pier five. The cofferdam is in for pier six. The pier seven cofferdam is installed and 50 percent of the pilings are complete.
For pier eight, the cofferdam is in place, piling driven and the concrete seal was poured. The piling has been completed for piers nine and ten and their footings poured. Most of the retaining wall footings on the north end of the bridge have been poured.
Later this year, bridge spectators will be in for a treat when the tied arch span, which will be constructed off site, will be floated into place using barges and lifted by cranes to its place on the deck.
When completed in 2013, MnDOT officials say the new bridge will be a highly redundant and robust structure with a 100-year life span. The visual elements including overall design, lighting, color, public art, railings and public areas near the bridge will make it a landmark for future generations of travelers and commuters, according to MnDOT officials. CEG
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