River erosion near Mankato municipal well

The Minnesota River is increasingly encroaching on Well No. 15 in Land of Memories Park, which supplies 30% of Mankato’s water.

The retreat of the riverbank along the Minnesota River on Mankato’s west side has rapidly accelerated in the past two years, bringing the river to within about 15 feet of a primary municipal well.

“Now we believe we’re in an emergency circumstance,” City Manager Pat Hentges said. “... And I think we need to make that argument (to the Legislature.)”

The potential threat to Well No. 15, which Hentges said provides about 30% of the city’s water, has been obvious for several years. But the amount of time the city has to fix the problem is suddenly growing short as more and more riverbank washes away.

“(In) 2013, we lost 13 feet of the bank. 2016, we lost another 8 feet of bank. 2018, we lost 23 feet,” he said.

Increasing rainfall has left the river levels high for months longer than was once typical. That has continued in 2019, and the distance between the river and the fence around the wellhead appears to be less than 15 feet — down from 73 feet a decade ago.

A major rainfall or a rapid spring snowmelt that pushes the river above flood stage could wipe out that final margin between the river channel and the well, according to Hentges.

“Basically, we could have one more major storm and lose that 15 feet,” he said.

While the well — which pulls water from sand below the Blue Earth and Minnesota rivers — provides nearly a third of the city’s water, its loss wouldn’t mean a shortage of drinking water during normal times. Other wells that pull water from the Mt. Simon aquifer could be tapped for a larger percentage of the city’s water needs.

But Well No. 15 allows the city to avoid contributing to the depletion of the Mt. Simon aquifer, which provides all or some of the drinking water to more than a million Minnesotans from the southern portions of the Twin Cities metro area as far south as Martin County. State officials are concerned that water is being drawn from the valuable aquifer at a rate that exceeds the aquifer’s regeneration.

Well No. 15 is also critical in supplying water during high demand periods in Mankato.

“If we lost the whole well, we would begin to have some difficulties,” Hentges said. “... If it was in August, we’d have full watering bans on.”

The problem is severe enough that city leaders are altering their planned request to Gov. Tim Walz and the Minnesota Legislature during the 2020 legislative session.

Earlier this summer, the plan was to seek $11 million from the state bonding bill the Legislature is expected to approve next spring for construction projects across the state. Under the original proposal, most of the money would have been dedicated to a slowing and filtering of water flowing into Mankato from the surrounding countryside before it reaches the river.

The centerpiece of the water-quality plan was the creation of a mammoth wetland on Mankato’s southeast side.

The new plan is to drop that portion of the request down to about $6 million and seek more money for anti-erosion efforts in Land of Memories Park, where Well No. 15 is located, and further downstream near Riverfront Park and the city’s sewage treatment plant.

“This (riverbank) stabilization needs to have a greater share because it’s more of an immediate problem,” Hentges said. “... We’re just in the middle of recalibrating what we’re asking for.”

The pitch to lawmakers and the governor is two-fold: that the funding will protect major public assets and that it will reduce the amount of sediment/pollution flowing downstream to the Mississippi River.

Area lawmakers understand the urgency of the issue, he said. They get that Mankato alone cannot shoulder the financial burden of problems stemming from the increasing volumes of water flowing through the city from a 37-county drainage area. And they recognize that stabilizing riverbanks would result in less sediment flowing downstream to the Mississippi, Lake Pepin and beyond.

He has hope that a majority of lawmakers from across Minnesota will ultimately be persuaded.

“If the state’s priorities aren’t with protecting the waterways, with protecting critical economic assets, I don’t know what the heck they’re spending it on,” Hentges said.

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