On an unseasonably frigid day in mid November, Matt Diebel walked through inches of snow toward an unassuming, semi-frozen pond on the western edge of Stoughton.
It’s ringed by the Stoughton Walmart Supercenter, a senior living facility, a new Hilton hotel that has taken shape in the last few months and farmland that’s the site of a proposed housing development.
Though the small pond might not look like anything special, it’s the remnant of an ancient era in the natural history of the upper Midwest, explains Diebel, the watershed coordinator for Dane County.
This kettle pond – from which the surrounding development, Kettle Park West, gets its name – is one of many such bodies of water in this region of Wisconsin, left behind by receding glaciers around 10,000 years ago, he says.
Today, state scientists say the kettles are threatened by the dual pressures of development and climate change, which are changing both how the ponds look and potentially, the habitat of the creatures who call them home.
As Forward Development Group prepares to build a housing development known as the Meadows at Kettle Park West on the pond’s northern and western sides, the ponds may face even more stress from human activity.
That concern has caught the attention of city leaders, who this month voted to add funding for wetland restoration as part of a $3 million contract to provide public funding for the housing development. But ensuring the ponds are protected during construction and beyond is mostly in the hands of the developer for now.
So far, the developer and its associated engineering experts have been taking a variety of precautions to prevent pollution, including blocking stormwater runoff from the hotel construction site. And obtaining a permit for construction requires engineering the site to maintain or improve water flow to prevent flooding.
Those interventions are essential, experts say, because the ponds are important habitats – either permanently or temporarily – to many species of wildlife. And with no natural inlet or outflow into the rest of the watershed, such ponds are particularly susceptible to both flooding and pollution, which state regulations do not fully cover.
Taking in the pond behind the Walmart, Diebel says it looks very different from when he was growing up in Stoughton. He decided to become a scientist specializing in watersheds after spending his youth on the Yahara River, and he recalled how during the 1980s, the pond sometimes dried out completely.
“It hasn’t happened in recent years,” he says. “It’s so wet now.”
The natural history of the kettle ponds begins with ice, specifically the Laurentide Ice Sheet, a mass of ice which once covered most of Canada and large parts of the northern United States. When it began to recede, it revealed depressions in the landscape that later filled with water, forming ponds with no water flowing in or out of them, and filled only by rainfall or groundwater.
Other ponds dot the landscape, some with names like Virgin Lake, others named after the families who once owned the nearest farm. A few have no label at all.
Although humans have given them names in recent years – geologically speaking – Susan Graham, a senior water resources management specialist at the Wisconsin Department of Natural Resources, said the ponds predate any human manipulation of the landscape.
Their nature has changed as the climate and their surroundings change, as well, said Eric Rortvedt, a water resources engineer at the DNR.
Rortvedt said that as rainfall has increased in recent years, and development has left the extra water with fewer places to go, ponds like the ones in Kettle Park West have become fuller.
Without careful rainwater management, said Rortvedt, this can cause serious flooding issues in nearby areas.
Critical to wildlife
Kettle ponds are either home or a critical stop-off point to many varieties of wildlife, though their inherent shallowness and tendency to change dramatically in depth during wet and dry periods limits the kinds of animals that can survive in them.
At the pond next to Walmart, Diebel points out several structures on the north side of it. They’re muskrat homes, domes built by the rodents by pulling marsh plants through holes they’ve made in the ice.
Though the body of water looks otherwise empty on this icy day, muskrats are far from the only creatures who depend on kettles for survival.
Various kinds of turtles, amphibians and pollinators make their homes in the kettle ponds, Rortvedt said.
As migratory birds travel south for the winter, the kettle ponds scattered across the landscape of Wisconsin provide pit stops for food and water, adding further to the diversity of animals who call the ponds home.
And although it might seem surprising for bodies of water with no inlets or outlets, there are fish who make their home in kettle ponds, particularly small fish like minnows, Rortvedt said.
Graham says the fish generally make their way to the kettles when migratory birds land in other bodies of water, and reeds or other plants with fish eggs attached to them wrap around their feet and legs, then fall off in kettle ponds, where they hatch and form populations of fish.
“Critters have a way of getting around,” Graham said.
In addition to protection against flooding, the structure of kettle ponds makes it particularly important to keep pollution out of them, explained Paul Dearlove, a senior director of watershed initiatives at the Clean Lakes Alliance, an environmental advocacy organization.
Because water cannot drain in or out of the ponds, he said, any pollution that gets inside them stays there, potentially harming anything that lives in the ponds.
This can include everything from gas leaking out of cars in the parking lots that proliferate around developments to heavy metals from the cars themselves, he said. It can also mean pollutants such as nitrogen and phosphorus, which can come from either landscaping around developments or nearby agriculture. Construction sites in particular, can pose a danger.
At the construction site of the Tru by Hilton, Diebel pointed out a few of the measures the developer is taking to prevent contamination. Bags have been placed in the surrounding storm drains to catch debris, and black strips lining the borders of the building site called silt fences and are meant to catch sediment that might otherwise wash off the site.
Bill Dunlop of JSD Professional Services, which handles the stormwater engineering for the Kettle Park West development, explained that most of the measures taken to preserve the wetlands in the area focus on removing dirt from the water, or oil and grease runoff, as well as keeping the water in the ponds as close to the natural level as possible.
“The objective is to stay within a one-foot bounce,” said Dunlop, the “bounce” being the amount the water can fluctuate within its natural range.
Dunlop said JSD first allows runoff to sit in a detention pond near the kettle where some sediment can settle before being pumped into an infiltration basin where it can gradually seep back into the soil. This helps protect the area from flooding and stops some pollutants from reaching the water.
But as Diebel pointed out, these measures are designed to meet regulations requiring that most, but not all pollutants are kept from leaking into the water. Even if all the rules are followed, he said, pollutants could get into the pond.
Then there is the question of who is ensuring that adequate measures are being taken to protect the ponds.
Rortvedt said the City of Stoughton is responsible for overseeing the management of the kettle ponds and any surrounding development.
But Rodney Scheel, the director of planning and development for the city, said JSD, which has the same owner as FDG, is responsible for the permit allowing development on the site of the kettle ponds.
Scheel said the pond will probably be managed again by the city at some point, but for now, the people responsible for making sure development around the kettle ponds don’t harm those ponds are the developers themselves.
The city’s development agreement with the developer, years in the making, is one attempt to ensure protection for the pond and possibly even improvement in its habitats.
The Common Council approved the contract May 12, and it includes a provision providing about $100,000 of tax-increment financing for the restoration of the wetland near the homes. That will be funded from taxes generated by increased property values in the area, as well other subsidies to the developer in the deal.
Ald. Regina Hirsch (Dist. 3), a primary advocate of the wetlands restoration clause, has a doctorate in wildlife biology. She said the restoration would address at least one issue with the wetland – the introduction of non-native species to the area through agriculture.
She pointed to the proliferation of plants like reed canary grass planted by farmers in the area decades ago without the knowledge that they might harm the local environment.
Hirsch said the restoration of the wetland will mean removing the invasive plant species in the area and replacing them with native species that would attract more of the animals, including migratory birds and waterfowl that should be frequenting the ponds.
Hirsch said that with the restoration being built into the project, the natural environment around the ponds will benefit and will add value to the land, as home buyers will pay more for healthy natural scenery around them.
“It should be a win-win,” said Hirsch.