Record-breaking rains in Minnesota led to flooding, affecting construction crews of S.M. Hentges & Sons Inc. on a highway project in Henderson. High water levels halted operations, causing delays and damage to erosion control. Crews now face significant catch-up work to complete the $30.6 million project.
Photo courtesy of Dick Rohland
Two dozen pieces of heavy equipment made up of Cat, John Deere, Volvo, Bell, Hamm, MTS, Bogota, JLG and Link-Belt machinery, which includes blades, rollers, excavators, wheel loaders, rollers, scrapers, skip loaders and cranes are on the site.
After several years of hot, dry weather, record breaking, monsoon-like rains rolled into the state of Minnesota this spring and stubbornly held a tight grip on the region going into early July.
Residents and businesses in many smaller communities throughout the state have endured flooding in their streets and homes, in some cases over-powering local storm sewer systems.
Photo courtesy of MnDOT
It also has impacted the state's highway system with road and bridge closures and short construction delays.
Road crews of S.M. Hentges & Sons Inc., the general contractor for a highway project in Henderson, Minn., a small farming community of 900 residents located in the Minnesota River Valley of southwestern Minnesota, are facing more than typical construction delays.
On this project, one of three roads running in and out of Henderson, rising waters of the nearby Minnesota and Rush Rivers quickly overflowed their banks from record-breaking rainfall and covered most of the project length.
By late April, portions of the project were impacted by high water.
In June there were more significant impacts to the project when good portions of the project were under water, halting most of the project operations.
"At the flood's peak, which set a new record by 1.8 feet, most of our 3.6 mile stretch of Highway 93 was under water to varying degrees," said Adrian Anderson, construction engineer, Minnesota Department of Transportation (MnDOT). "At the north end near the levee, the work area was under five to six feet of water in some places."
The scope of the $30.6 million project includes the reconstruction of 3.6 mi. of Highway 93 between Highway 169 and Elm Street. The roadway will be raised up to 8 ft. to stay dry during 100-year flood events. The bridge crossing the Rush River will be replaced and an additional overflow bridge will be constructed to allow for Rush River flood relief.
An overflow bridge at this location is necessary because the Rush River has some interesting behavior patterns during rain events, Anderson said.
"It rises quickly and then recedes quickly, even when the Minnesota River is not in a flood state. When this happens, the Rush River will over-top Highway 93 north of the Rush River Bridge — you can see old scour lines on satellite images in the field east of the highway, and north of the Rush River bridge. The overflow bridge will bridge this area so if the Rush River over-tops, then no closures are needed. This also allows for that water to pass freely as it did before without obstruction," Anderson said.
Coming out of an unusually mild winter, Hentges construction crews hit the site March 1 for clearing and grubbing operations. April 15, crews set up the detour and closed the road.
Then it started raining and held a holding pattern for nearly three months statewide.
According to data from the National Oceanic Atmospheric Administration (NOAA), average rainfall from April through June for this region of the state is 12 in. This year, close to 20 in. of rain fell for the same time period.
By the third week in April, floodwaters began rolling over the existing pavement of Highway 93 and brought major construction to a standstill.
"Up to that point, we had set up perimeter controls with super duty silk fence and sand totes," said Ryan Kniefel, director of project management, S.M. Hentges & Sons. "And we still had utility conflicts. There was a gas main in the way and some communication lines, so we were basically on standby for three to four weeks.
Photo courtesy of S.M. Hentges & Sons Inc.
"And of course when they [utility conflicts] were out of the way, that's when the flooding came up. We had only been able to move embankment material to build up the road and the surcharge for two days out of two months. Now at this point, we're basically behind four months because of the utility conflicts and the flooding. It was basically abandoning ship and waiting until we could go back to work."
Past flooding of Highway 93 prompted this highway rebuild to combat future road flooding. And flooding on this section of highway is more than just a quirk of nature. For the residents of Henderson and commuters, flooding has become a way of life for them.
The city of Henderson has been hit especially hard in recent years with road closures reaching an all-time high. In 2019, both Highway 93 and Highway 19 were closed for a total of 61 days between March 16 and July 5. In 2020, there were five closures for approximately 22 days according to MnDOT.
As the floodwaters began to overtake the road pavement, the contractor was able to continue some work.
Hentges crews were able to get some excavation done for the Ridge Road box culvert before moving their equipment off site.
"Opportunities to work elsewhere would have required pavement removal, which given the flooding forecasts created concerns for further damage and site accessibility issues," Anderson said.
Though the highway may have been out of sight as the waters washed over the highway, it was not out of the minds of Kniefel and Anderson.
For Anderson, it was mainly safety and access.
"As the waters were coming up the main concerns were safety and access. Coordination with the contractor for their equipment and materials to get to safety was critical, as well as thinking about other contingencies that may come up.
"On my end, there was a lot of coordination and messaging that needed to get done such as the emergency detour — the flooding cut off the original detour route — and emergency service access to residents on Highway 93. Throughout all of this, schedule impacts lingered in the back of my mind, but I knew that the floodwaters would have to recede before we could fully realize what those impacts are," Anderson said.
Kniefel had the possible effects of the surcharge periods on the schedule caused by the lengthy construction delay on his mind as he and his crews were suddenly left idled and in limbo.
"For the surcharge periods, some of them are over a year long, so at this point, we're four months behind that. We're hoping the surcharges settle faster than anticipated but we're not seeing where we can make up schedule time. A day in June is not the same as a day in December because of freeze up conditions and everything else that goes along with a Minnesota winter," Kniefel said.
As the water began receding in early July and forecasts showed a dryer period coming up, damage could be clearly seen.
Though none of the existing pavement was washed out or damaged, the flood waters left a nightmare of mud and muck and extensive damage to the erosion control equipment.
Tree branches and everything else floating down the river can do a lot of damage to erosion control.
"We had the geotextiles for underneath the roadway, they were stored in a little lay down area on the south side of the levee," said Kniefel. "We ended up pulling those up to the levee to hopefully keep them out of the water. But because of how high the floodwaters came up because they peaked at nearly two feet above the previous record, the water ended up sweeping some of those textile rolls away. We ended up trying to chase these down. We still have some more to chase down that we lost in the flood waters."
By the third week in July, the water had receded to its original depth, giving Hentges' crews an opening to replace all the erosion control devices that were mangled or lost during the flood.
Thankfully no one was injured during the record breaking flooding, but it did leave some residents landlocked.
"There were a few properties that were landlocked due to these high floodwaters, unfortunately," said Anderson. "Given their proximity to the river this is not their first time being flooded out. Having spoken to some of those residents, some of them have other places they stay temporarily, or others have even traveled by boat to Ridge Road to get to and from their homes. About half of the homes that you would have seen do have a back access road up onto the bluff that leads back into town."
Hentges' crews have a lot of catch-up work ahead of them to literally dig into.
Photo courtesy of S.M. Hentges & Sons
Crews will place 373,000 cu. yds. of fill throughout the entire project (not including surcharge material), and 4,100 cu. yds. will be used for the levee.
Other quantities include the installation of 30 mi. of piling; 21,700 tons of bituminous pavement; 469,000 cu. yds. of embankment and surcharge material; and 160,000 sq. yds. of geotextile fabric.
Two dozen pieces of heavy equipment made up of Cat, John Deere, Volvo, Bell, Hamm, MTS, Bogota, JLG and Link-Belt machinery, which includes blades, rollers, excavators, wheel loaders, rollers, scrapers, skip loaders and cranes are on the site.
Anderson admits that at this stage, it's too early to come up with a revised construction schedule.
"As the flood waters continue to recede, MnDOT and Hentges will continue to evaluate what damage has been done. As of right now the only damage we have identified is some reworking of the embankment that was placed prior to the flooding and re-installation of BMP's that were damaged during the flooding. With the flood waters still on the eastern portion of our work area, the true schedule impacts have yet to be realized and is something that MNDOT and Hentges are in continuous conversations over." CEG
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