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McGregor Lake area restoration continues

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Large hoses were used to transfer sediment and fine material from dredging into backwater habitats constructed to encourage new wildlife and plant growth.

Areas south of the Marquette-Joliet Bridge where wetlands have been developed to increase bio-diversity. Plant life, including trees, and fisheries were targeted as concern areas.

An aerial shot of the McGregor Lake area between Prairie du Chien and Marquette, Iowa. Restoration work began in 2020, and its initial phase is expected to be completed in 2025. (Photos by Steve Van Kooten/Courier Press)

New habitats, improved waterways, landscape to help preserve river ecosystems

 

By Steve Van Kooten

 

On Prairie du Chien’s side, the Mississippi River embodies the invisible line between Iowa and Wisconsin. Along its shores and islands, fishermen take boats on the water in search of a summer catch, and in winter, they bore through its ice to hook a blue gill. Families walk the trails cut into the brush to see bits of the refuge — an untamed piece of Wisconsin.

Above the river, commuters cross the Marquette-Joliet Bridge between Prairie du Chien and Marquette, Iowa. They can see the landscape change with each passing season. 

It’s not just cosmetic changes. In the water and on the sands of the islands, a series of ecological blows left the McGregor Lake’s habitats weakened and susceptible to disease, invasion and decay.

It’s a death by 1,000 cuts.

 

Dead trees

Some of those cuts are deep wounds that compromised McGregor Lake’s ecological health.

According to Kendra Pednault, manager of the Upper Mississippi River National Wildlife and Fish Refuge McGregor district, those cuts came in many forms, and each one led to a decrease in biodiversity in McGregor Lake’s habitats.

A feasibility study completed in April 2019 by the U.S. Army Corps of Engineers St. Paul District said prolonged flooding caused the reduction of tree species in the area. Less resilient species died off and seedlings were unable to root either due to longer periods of water inundation or sunlight deprivation from invasive grass, which grows earlier in the season than native vegetation.

Before flood damage took its toll, agriculture and urban land development caused the Upper Mississippi flood plain to lose approximately half its forests. When the lock and dam installations in the early 1900s changed water flow, even more forest area was lost.

At the same time, invasive grass species, diseases and insects hampered several prominent species, including elm and ash trees.

The U.S. Army Corps of Engineers reported 85 percent of the area’s tree population was silver maple in 2018, with half a dozen other species each making up 1–2 percent of the remainder.

A disease outbreak or fungus can cripple the habitat’s resources when there is low number of abundant species.

The effect permeates through the environment: fewer trees mean fewer food sources and shelters for animals, fewer verdant areas for other plants to find shade from direct sunlight and fewer habitats for insects.

 

Restoration

After the feasibility study determined McGregor Lake needed help, it became one of the Upper Mississippi Restoration Program’s projects. It is one of three currently under the St. Paul district corps of engineers’s onus.

Congress first authorized the Upper Mississippi Restoration Program in the 1986 Water Resources Development Act to rebuild and stabilize areas of the river. The federal government reauthorized the program in 1999.

“We’re really in an unprecedented stage in habitat restoration at the Upper Mississippi River,” John Henderson, project manager for the McGregor Lake project, said. “We’re going to make a substantial impact throughout the Mississippi River.”

Henderson, a civil engineer with the corps, credited several agencies’ ability to work together, including the Wisconsin and Iowa Department of Natural Resources, the U.S. Fish and Wildlife Service (USFWS) and the state of Wisconsin, as the reason for the UMRR’s success.

“We’ve learned to work together with contractors [and] community agencies to continue helping the Mississippi, either by studying it or enhancing it,” said Henderson.

The Corps explored more than 40 alternatives, including a non-intervention option, and determined the degradation of plant species, wildlife habitats and the natural barriers between McGregor Lake and the east channel of the river required intervention.

The McGregor Lake project had a first cost of $23.7 million, according to the 2019 feasibility study. The McGregor Lake Habitat Rehabilitation and Enhancement Project was responsible for dredging and relocation of sediment material, which accounted for approximately $6 million in project costs. The remaining $17.7 million is 100 percent federally funded by the USFWS.

Henderson said the restoration operation is expected to finish by 2025, but tree planting will continue for several years.

 

Means and methods

Near the end of the summer, mounds of sand rose up from the wetlands. The sand was dredged from the river’s main channel and hydraulically transferred into the backwaters with hoses. Over time, the new soil absorbed and displaced the water, leaving the fine behind.

“What you are seeing is the construction [and] building of elevated islands and areas for forest restoration,” said Pednault. “The fine material has more organic matter, which provides better habitat to grow plants and trees. It also holds the sand in place. Ultimately, you end up with a higher place for trees to grow and, basically, not drown as a result of higher water levels.”

“Thin layer placement is a newer concept we’re trying in the UMRR to target a much larger area on a less intrusive scale,” said Henderson.

The corps’ new method was less disruptive to the wildlife than “traditional island building” and optimized the project’s habitat dredging to create better environments for plants, animals and people.

“When we’re all said and done, not only will we have moved 500,000 yards of clean river sand, we will also have done 2000,000 yards of backwater dredging. That will help back water fisheries and increase recreational opportunities.”

 

Goals

The U.S. Army Corps of Engineers plan has multiple goals with decade-long benchmarks to measure area sustainability.

Workers will plant seedlings in the area to increase tree species and age biodiversity. The goal is to see a 50 percent or greater survival rate after ten years.

Dredging will create new depths in areas where fish overwinter, with a goal for more than half of all designated overwintering areas to be 7.4 feet deep or more to create desirable habitats for fish. There are 92 species of fish in the project area, of which 34 are considered abundant. The ten-year goal will measure blue gill and largemouth bass population by hour, with more than 100 blue gills and more than 50 largemouth bass designated as successful results.

Other goals include the increase of emergent and submergent vegetation growth; the reduction of shoreline erosion, particularly on the isthmus that separates the lake from the river’s east channel; and the preservation of habitats, species and culturally significant sites in the project area. There are more than a dozen federally or state-listed species in the McGregor Lake area and 11 archeological sites.

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