Mankato pursuing establishment of new wetland park

Jul. 16—Songbirds singing, waterfowl paddling, reptiles scurrying, cattails and bulrushes swaying in the breeze. And providing access to it all, a grassy path encircling what would likely be Mankato's biggest piece of parkland.

For people walking along the marsh and amid the upland prairie on the city's southeast edge sometime later this decade, it will be easy to assume the sprawling piece of pristine ecology had always been there — that nature long ago did all of the work.

If the wetland park comes to be, though, it will only be because of a lot of imagining, lobbying, land-purchase negotiating, dam designing, neighborhood communicating, grant writing, environmental consulting, seed planting, weed controlling and more.

"It's really exciting," City Manager Susan Arntz said of the prospect of returning a mile-long swath of farmland to nature.

Arntz was authorized by the City Council last month to negotiate the purchase of a 100-acre parcel that stretches from Monks Avenue to Pohl Road just outside city limits. If an agreement can be reached with the landowner, the property would represent the biggest piece of what ultimately could become a natural area of more than 150 acres.

A preliminary concept design of the Southeast Water Quality Project shows the wetland and adjacent green space covering most of that 100-acre parcel and roughly 70 acres of land in adjoining parcels.

For comparison, Rasmussen Woods Nature Area on Mankato's west side is 150 acres of marsh and forest; the Kiwanis Recreation Area on the north end encompasses 100 acres of Minnesota River floodplain; and the restored wetland and woodlands in Blue Earth County's Indian Lake Conservation Area south of Mankato covers 123 acres.

While the project can't be accomplished with the first parcel alone, completing that purchase could provide meaningful momentum toward obtaining the additional land.

"Take the biggest bite of the apple the first time," Assistant City Engineer Michael McCarty said.

Array of benefits

Providing a nature area for residents of the fast-growing southeast side of Mankato would be the most overt benefit of completing the project, but that wasn't the primary motivation when the idea was first suggested by former City Manager Pat Hentges more than six years ago.

The concept that would later evolve into the Southeast Water Quality Project was mainly about better controlling the flow of water through southern portions of Mankato, including water draining from agricultural areas south of town.

Restoring a large wetland, which has been farmed for decades following the draining of the marsh, would slow the torrents of water following heavy rains that flow through a ditch, culverts and ravines toward Stoltzman Road and eventually into the Blue Earth River.

"If we're able to retain water on the land, we're able to control peak flows and limit erosion in those ravines," McCarty said.

The wetland would ease some of the burden placed on the city's stormwater retention ponds during mega-rainfall events. When those storms hit at a time when the ground is already saturated, the retention ponds can be overwhelmed. When that happened in 2014 and 2016, homes in the Rosewood Drive/South Brook Circle neighborhood just west of the proposed wetland suffered flood damage.

The Southeast Water Quality Project aims to reduce pollutants flowing into the Blue Earth and Minnesota rivers, too, because the wetland would allow marsh plants to absorb nitrates and phosphorus before the water moves downstream.

"It would be an improvement for the entire watershed," McCarty said. "It helps Mankato residents but also folks that are outside the city along the waterways as well."

Finally, the city would like the project to serve as evidence that municipal drainage improvement work can be done without negatively impacting tile systems in adjacent farmland.

"Trying to be a good neighbor," Arntz said.

State regulations also will be in play as the city tries to strike the right balance with the project, said Mark Manderfeld of the Blue Earth County Property and Environmental Resources Department.

"If changes are proposed to a drainage system, including the impoundment of waters as necessary for the creation of a wetland, there is a formal petition process that landowners must follow," Manderfeld said, speaking generally since the county hasn't been involved with the project. "State statute is written in such a way to encourage wetland restorations, while not impairing the drainage system or depriving the benefitting landowners of the system."

When that balance is struck and wetlands are restored, the benefits are many, Manderfeld said, enhancing groundwater recharge, water quality improvements, wildlife habitat, flood control and more.

Which is what makes an extremely challenging and complex initiative worth attempting, McCarty said.

"We're excited to be able to do a project that hopefully checks a lot of boxes."

A learning environment

Jeremy Maul, a board conservationist for the Minnesota Board of Water and Soil Resources, isn't associated with the project but said he immediately liked its location.

The nature area would butt up against Mankato's outlying neighborhoods and would be only about a third of a mile from Rosa Parks Elementary School.

"A nature area for people and an educational area for kids — and adults, too," Maul said.

In fact, the Rosa Parks students could potentially be involved even in the creation of the park. When Maul lived in Madelia, his daughter's fifth grade class helped seed a wetland restoration project.

"Some of those kinds of things are an interesting idea that they maybe haven't thought of," he said. "Getting kids out to those areas to see the changes — from what was once wetland and then farmland and then back to wetland again."

Arntz and McCarty both talked about the value of bringing a nature area to a part of town that's without one. And it's a section of Mankato that has some lower-income neighborhoods the city is particularly eager to serve with new passive recreational spaces.

"It's not going to have a ballfield or soccer field or playground," Arntz said of the features people often associate with municipal parks.

Those sorts of amenities already exist or are in the planning stages nearby, but the wetland project offers a unique opportunity to provide a unique environment for that side of town.

"People really value the ability to walk and be in natural settings," Arntz said.

If the city is successful in re-creating a 150-plus acre wetland and nature park, visitors will find plenty to look at and listen to, Maul said.

"They're going to see all sorts of songbirds they're not going to see otherwise," he said.

There would be butterflies and bees, frogs, salamanders, toads, snakes, turtles, raccoons, occasional deer and countless species of flora.

"It's going to be the whole gamut, really, especially a project like this because it looks like there would be a fair amount of upland that will go with it," he said.

First things first

Mankato's Public Works Department, which typically engages in more urbanized construction work, will be relying on experts when the project reaches the ecology stage.

"We've been working with a consultant," McCarty said. "We'll be looking for advice from the Board of Water and Soil Resources and the local conservation district — where they've seen success with projects like this in the area in the past."

Before the plantings, though, would come some dismantling of the existing drainage system on the land. Tile lines and ditches would need to go. A dam-like water-control structure would need to be built.

Prior to the construction, there would be discussions with adjacent farmers and studies of their tile systems to ensure they aren't negatively impacted.

And before that, the land needs to be acquired.

"I think that's probably the biggest challenge we face with this overall project," McCarty said.

The price of ag land has been steadily rising in recent years, and inflationary pressures can be especially intense adjacent to a growing city.

In 2020, Mankato requested nearly $2.5 million from Minnesota's Clean Water, Land and Legacy Amendment fund but was granted just $1.35 million. The City Council has slated $890,000 in sales tax revenue for the project — money that could also be used for land acquisition. But in those three years, soaring land prices may have shrunk the buying power of the pot of money.

"We probably need at least double what we've got if not more," McCarty said of the overall project. "I think that's going to be the biggest hurdle — keeping up with the increases in land values."

The Legacy Amendment grant requires the purchases to be completed by June 30 of next year, so the city has that complication to add to an already complex project.

Even if the land is in hand, more funding will be needed for the establishment of the wetland, upland and basic trails.

"Once we have a better handle on design, it would be very likely we'd go back and look at other grant possibilities for construction," Arntz said.

If funding is cobbled together, the land is acquired, the designs are completed, the water-control structure is built and the wetland plants are planted, one other outside partner will need to cooperate.

"There's also a lot of nature you're relying on to make it successful," McCarty said, noting Mother Nature needs to put the "wet" in any wetlands. "I wouldn't want to be trying to establish wetlands with the weather patterns we've had this year and last year."

As multifaceted and arduous as the project is, Arntz isn't losing faith.

"We sure are hopeful," she said.