ST PETER — In an effort to keep highways 169 and 22 from going underwater in floods, the state will spend an estimated $8 million to $10 million in 2015 to raise the roads.
The projects — for Highway 169 in two spots near St. Peter as well as Highway 22 just east of the city — were funded from a $50 million fund set up by the Minnesota Department of Transportation after the fall floods of 2010.
The Highway 169 projects involve raising the southbound lanes during a repaving project. The cost to raise the road is an estimated $4 million to $5 million, though that’s a “very rough” estimate, said Scott Morgan, the district bridge and hydraulics engineer for MnDOT.
Plans call for Highway 169 to be raised in two spots: at the north end of St. Peter, near the Treaty Site History Center, along with a stretch a few miles north of the city. The road will be raised above the water level of a 100-year flood, defined as having a 1 percent chance to happen any given year.
Only the southbound sections will be raised; northbound traffic could be diverted onto the other lanes during a flood.
The second project is a bit more complicated.
About 500 feet west of the Highway 22 bridge over the Minnesota River — just before it enters the south end of St. Peter — there is a slight dip in the road. That low point flooded in the fall of 2010.
But the road can’t simply be raised.
That’s because the dip acts as part of the river during a flood. Filling it would raise floodwaters upstream.
“It would be significant,” Morgan said.
The Department of Natural Resource permit doesn’t allow MnDOT to reduce the river’s capacity.
So the plan is to build another bridge between the current bridge and St. Peter. Floodwaters would travel below the smaller bridge.
Why wasn’t this second bridge added along with the first?
Morgan said at that time, in the early ’90s, there hadn’t been large floods for a long time. It would have been harder, in other words, to justify spending a lot of money when flooding didn’t seem as likely.
The cost estimate for this project is the same as the first, roughly around $4 million or $5 million. They’re both scheduled for 2015.
The goal for both projects, Morgan said, is “to get a good corridor open between Mankato and the Twin Cities to get through a 100-year flood event.”
The department also looked at whether it was worth it to spend this much money for a relatively rare event.
Closing these highways for weeks at a time causes delays that result in millions of dollars in wasted spending, Morgan said, especially in freight.
The department is also seeking funding to raise Highway 169 between Mankato and St. Peter in 2016, when a paving project is scheduled. They don’t yet have the grant, though.