Minnesota flooding: Rapidan Dam near Mankato holds, roads and state parks closed (2024)

Authorities in Blue Earth County continued to monitor the imperiled Rapidan Dam on Tuesday after the rain-swollen Blue Earth River carved a new channel around the structure.

As of Tuesday morning, the dam southwest of Mankato remained intact — but was bypassed on its west side by a new river channel the rushing water carved out on Monday. Authorities said it happened after debris piled up against the more-than-century-old dam in the wake of recent torrential rain.

While the dam has partially failed since water went over the top and around the side, the dam structure has not broken.

Blue Earth County Engineer and Public Works Director Ryan Thilges said even if the dam fails, the Blue Earth River would only rise by a few inches. Thilges said because the water is not backing up at the dam, it would not result in a major surge rushing downstream.

“The structure of the dam is still intact and in place. As you can see right behind me, the water ran around the west edge of the dam and is now eroding the slopes to the west and to the north,” Thilges said.

If the dam does fail, Thilges is more concerned about released sediment flowing downstream.

County officials said Tuesday that the volume of water flowing was slightly lower than it had been on Monday.

That new channel washed away an electrical substation below the dam, knocking out power to hundreds of homes on Monday. Xcel Energy said that service was restored overnight.

Blue Earth County said the Rapidan Dam has experienced regular flooding — but those floods have taken a toll on the structure.

There are no large-scale evacuations in place below the dam.

County officials said Tuesday that there had been routine monitoring of the dam starting on Saturday. As of Sunday evening, they said, “the dam exhibited high flows and additional debris, but still displayed adequate capacity.”

Problems with water going over the dam, and then carving the new path around it, were first reported early Monday.

A home adjacent to the dam that’s been threatened by the new river channel remained intact as of Tuesday morning — but officials said the water continues to erode that slope.

After viewing flood damage in southern Minnesota by helicopter Tuesday afternoon, Gov. Tim Walz and U.S. Sen. Amy Klobuchar said the state is likely to be eligible for federal disaster aid.

“I am not an engineer, but looking at that dam and seeing the severe damage there as well as washed out roads in Minnesota, I believe we could well be into our $10.5 million. That is the level at which federal aid would tick in for public infrastructure,” Klobuchar said.

Public Safety Commissioner Bob Jacobson said that initial damage assessments are underway in northern Minnesota, and he’s met with staff from the Federal Emergency Management Agency.

Walz said damage assessments will take place alongside cleanup. He said a complicating factor is that water levels are still rising in many southern Minnesota.

Rapidan Dam

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U.S. Highway 169 closed

Travel in the Minnesota River valley got a lot more difficult late Monday and early Tuesday, as rising river levels forced the Minnesota Department of Transportation to close two stretches of U.S. Highway 169.

The highway is closed between Mankato and St. Peter, and also between St. Peter and Le Sueur. That means all the traffic from that busy four-lane highway is being detoured onto two-lane state and county roads.

Both Minnesota River bridges at St. Peter are also closed. And some on- and off-ramps along Highway 169 in North Mankato also are closed due to flooding.

Find updates on state highway closures on MnDOT’s 511 site.

To the east, Gov. Tim Walz deployed the National Guard to the city of Waterville on Monday. He called the flooding there and across the state “catastrophic,” and said it could rival historic flooding in 1997 and 2007. Walz and Sen. Amy Klobuchar are set to make an aerial survey of southern Minnesota flooding later Tuesday.

Flooding in southwest Minnesota

State Highway 60 through Windom was also among roads closed due to flooding on Tuesday.

The city is experiencing historic flooding. The Des Moines River at Windom is at its highest level on record. The National Weather Service said it’s forecast to stay near that record high before slowly receding late this week.

Windom City Council member Jenny Quade said city crews have been working hard to keep up with the rising water.

“They put a barricade up to say, ‘there’s water coming up,’ to ... warn you beforehand,” Quade said. “But by the time they get all around the city ... they’re having to go back and move those barricades because the barricades are getting under water.”

Some residents have evacuated homes near the river on the northwest side of Windom. The Red Cross has set up a shelter at Jackson County Central High School in the city of Jackson — which also is experiencing flooding.

Jackson city officials reported Tuesday that work continued to reinforce dikes protecting the town from the rising Des Moines River.

U.S. Highway 71 through Jackson is closed due to flooding.

Parks, trails close after flooding

State parks across Minnesota are recovering from recent heavy rains and flooding.

Underground tours at Lake Vermilion-Soudan Underground Mine State Parkwere halted last week after the park received more than 7 inches of rain in less than 24 hours. The DNR said underground tours will be suspended for at least three weeks while crews pump water out of the mine. Surface tours of the mine are still available daily.

Cave tours at Forestville/Mystery Cave State Park in southeast Minnesota are also on hold due to flooding. The pedestrian bridge to historic Forestville has been inspected and is open to use, according to the DNR, and the Big Spring trail has reopened to use.

Bison and prairie tours at Blue Mounds State Park in southwest Minnesota are canceled this weekend. The DNR says park staff will assess water levels on Wednesday, and they hope to be able to offer tours next weekend. The bison drive at Minneopa State Park near Mankato is closed due to flooding, as is the Minneopa Falls area and several trails within the park.

Fort Snelling State Park in the Twin Cities is closed until floodwaters recede and park staff can assess and repair damage.

There are washouts and damage on the Gitchi Gami and North Shore state trails in northeast Minnesota, according to the DNR. And the Minnesota Valley State Trail is significantly flooded.

The DNR is also urging caution on state water trails: ”High currents and floating objects are just two reasons to avoid paddling in flooded waterways.”

Manure overflowing

More than a dozen manure pits are overflowing at feedlots in southwestern Minnesota.

State agriculture commissioner Tom Peterson said the feedlots are working with the Minnesota Pollution Control Agency. He said the stormwater and manure has discharged onto farm fields and not into any bodies of water.

“Historic rainfalls can cause issues for manure management systems that are not designed to handle extreme amounts of rainfall and we are providing advice on actions they can take to avoid an overflow or lessen the impacts should one occur,” the MPCA said in a statement.

The MPCA said it’s received reports of 17 instances where liquid manure storage pits have overflowed on 15 cattle feedlots located in Nobles, Rock and Jackson counties.

“These storage areas hold highly diluted manure that is collected as part of stormwater runoff from the feedlots. The manure becomes further diluted once combined with the high volume of floodwaters,” the MPCA statement said.

The Minnesota Department of Agriculture and the MPCA continue to monitor the situation.

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