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Forestville Millpond Drawdown to Be Assessed

How well did the Forestville Millpond drawdown work to check the water body’s decline and improve the lake’s overall health? 

That’s what the County of Door hopes to learn from an evaluation that will take place over the next year as part of the project’s post-refill activities, and the Door County Board of Supervisors accepted a grant last week to fund the evaluation. To the $9,237.80 Lake Planning Grant from the Wisconsin Department of Natural Resources (DNR), the Door County Soil and Water Conservation Department (SWCD) budget will contribute $4,549.96, for a total project cost of $13,787.76.

“It’s going to let everybody know what the drawdown did for water quality, water depth, water clarity,” said Greg Coulthurst, county conservationist, by phone with the Peninsula Pulse a few days after the March 28 board meeting where the supervisors approved the grant.

“If it did minimal benefits, well, the public needs to know that, the county board needs to know that, and then we don’t do it again. If it does work, then we need to decide how often we do it.”

— Greg Coulthurst, County Conservationist

The drawdown is a temporary lowering of water levels by opening the sluice valve at the dam on the Ahnapee River, which originates in a wetland complex in Southern Door and travels 14.7 miles to its outlet to Lake Michigan in Algoma. The river’s Door County portion is about 8.5 miles, and at its northern point is the Forestville Millpond. The County of Door, which owns and operates the Forestville Dam, began the drawdown on Nov. 1, 2019, and began refilling the lake on Sept. 1, 2021.

The premise behind the drawdown was that once refilled, the millpond would be deeper and clearer due to compaction and oxidization of the exposed sediment; invasive aquatic plants, such as Eurasian watermilfoil and curly-leaf pondweed would be controlled, allowing for improved growth of native plants; and the dominant carp population would be reduced.

“Reductions of aquatic vegetation, compaction or removal of bottom sediment, and control of the rough fish population would be the greatest benefits of this measure,” according to SWCD reports dating back to 2018, when management options were developed and considered. “The elimination or reduction of the carp population resulting from drawdown would improve water clarity.”

The evaluation will test all of those premises. This includes vegetative analysis and water sampling to test for pollutants such as phosphorus, suspended solids and total nitrogen, as well as parameters such as temperature and oxygen levels “that define good water and the health of the stream,” Coulthurst said. 

The drawdown was also supposed to correct the mucky lake bottom with soil compaction, increasing the shallow water depth that had a maximum of six feet before the drawdown. 

A reduction of carp – another goal – may have worked, Coulthurst said. In October 2021, the DNR stocked the lake with fingerling bluegills and largemouth bass averaging 3.3 inches.

The Wisconsin Department of Natural Resources works with local partnering agencies to stock the Forestville Flowage with largemouth bass and bluegills to reestablish fish populations. On average, bluegills reach six inches, and bass 14 inches in four to five years. According to DNR fisheries biologist Nick Legler, the stocked fish will provide angling opportunities and may also benefit the ecosystem of the flowage by helping to control carp populations through predation or consumption of tiny carp fry.

“They are not going to invest money in restocking fish if that’s not the case,” he said. 

The studies and tests will be done throughout this spring and summer. Coulthurst said he wouldn’t expect the report on whether the drawdown worked to be ready until the end of 2024. 

Residents who live on the 94-acre lake have not been happy about the plans since the project was first developed. In the beginning, they accused the county of selecting the drawdown only because it was the cheapest management option. Eventually, their resistance grew to include people who didn’t live on the lake, and the Friends of the Forestville Dam was incorporated. 

In early 2021, the Friends group and 12 other plaintiffs, alleging county mismanagement of the drawdown, filed a complaint to stop it. The case was dismissed in January 2022.

One of the leaders of the Friends group, Christine Reid, in correspondence to the county board and speaking during its March 28 meeting, said it’s “good news” that the evaluation will be done. 

“We would like to be included, beginning to end of this evaluation,” she said. “We’ve asked to be included in everything related to the Forestville Millpond; it’s where we live. We’re taxpayers, and we want to be included in this.”

They also asked that the evaluation be done by an independent environmental engineering firm, rather than the University of Wisconsin-Oshkosh.

“I know that UWO has done work in the past; however, they’re on the payroll,” she said. “They do beach testing, well testing, and I feel that that’s a conflict of interest.”

Reached a few days after the county board meeting, Coulthurst said UWO would replicate the 2018 water-quality sampling tests exactly.

“We’ve been partnering with UWO for years on this project,” he said. “They’re taking the samples and sending them to a state lab. They’re doing exactly what they did last time so we can compare apples to apples. They don’t have any skin in this game.”

The county board’s unanimous passage of the grant March 28 was preceded by very little discussion. Only Supervisor Vinni Chomeau commented, saying she believed that people had lost sight of the drawdown objectives and what they had realistically hoped to accomplish. 

“There’s an impoundment behind the dam,” she said. “It’s been there for 100 years. The goal of the drawdown is to reduce the sediment so it settles. It’s not going to solve a 100-year impoundment behind a dam, but it’s going to help.”

Forestville Millpond drawdown information is available at co.door.wi.gov/954/Forestville-Millpond-Drawdown-Informatio.

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