Wetlands to Provide Environmental Benefits, Critical Habitat

May 14, 2014 - When the wetlands park in the Drexel Town Square (DTS) is completed, the developers won’t need to advertise for occupants. Thanks to smart planning and sound environmental design, the wetlands area will attract a variety of species from “pollinators” to butterflies, from turtles to birds and other wildlife.

The wetlands park encompasses 17 acres on the west side of the DTS development site. Eight of those acres are devoted to wetland with 9 acres devoted to upland plant communities of deciduous hardwood forest, tall and short prairie, and native shrubs. “When development concepts were starting to surface, the wetlands area was an enhancement opportunity we couldn’t overlook,” said Sue Winnen, City of Oak Creek environmental engineer.

Importantly, the wetlands area and its plantings are intended to provide wildlife habitat for many species including bees – “pollinators,” as well as the Monarch caterpillar which transforms into a beautiful butterfly. Bees and Monarchs have been declining in population in recent years for a variety of reasons including shrinking habitat (Monarchs) and disease (honey bees). The DTS wetland park will do its part to help address the problem.

The wetlands park area includes three storm water detention basins or ponds that will collect storm water runoff. These ponds are required by the Wisconsin Department of Natural Resources (WDNR) to compensate for the paved areas within the Drexel Town Square complex.

A wetland ecologist worked with engineers to design the hydraulically complex system that will manage the storm water to prevent adverse flooding of the planted areas.

One of the ponds will feature a floating wetland island made of a matrix of nontoxic post-consumer plastics vegetated with native plants. While it will be visually interesting, the “island” will be functional as microbes grow in the matrix of the island and the roots of the plantings will grow into the water below the island. The microbes and the plants will help to clean the water and reduce the amount of algae that forms.

The ponds, which will be 4 – 6 feet deep, are not stagnant however. As storm water and snow melt run-off is routed to one of ponds, the water is retained while particles settle. Water in the pond makes its way into the wetland area that serves as a sponge. The engineers designed the detention pond to buffer sudden changes to the wetland hydrology, to more closely mimic a more natural hydrology that will be beneficial to the native habitat. 

The floating island was funded, in part, by a $65,000 grant from the Fund for Lake Michigan. Since 2011, the Fund for Lake Michigan has awarded 70 grants to nonprofit organizations and local government agencies to improve the health of Lake Michigan and its communities. The projects focus on habitat restoration and reducing runoff and pollutants in the watersheds of Southeastern Wisconsin.

The Fund for Lake Michigan is a private foundation created by We Energies and two smaller utilities as a compromise to settle environmental disputes over the new coal-fired power plant built at Oak Creek. The Fund is overseen by representatives from We Energies, Madison Gas and Electric, WPPI Energy, WDNR, Clean Wisconsin and Sierra Club.

Vicki Elkin, executive director, Fund for Lake Michigan, said the Fund looks for ways to support initiatives that “marry economic benefits and water quality improvement.” The wetlands park does just that.

“The concept of a floating island represents the innovative use of a new, cutting-edge technology for improving water quality,” Elkin said. “We’re excited to be part of this project. It’s clear the City of Oak Creek is fully committed to sustainability and responsibly managing the storm water on this site.”

A prairie buffer -- plantings of grasses -- will surround the storm water ponds and wetland areas. The storm water ponds will have approximately 2.5 acres of open water and the wetlands will have approximately 2.9 acres of shallow, open-water habitat. Tree stumps will be left in some wetland areas for “turtle basking.” Turtles commonly use tree stumps or floating logs to warm themselves in the sun.

The U.S. Fish and Wildlife Service, in partnership with the WDNR and Army Corps of Engineers, will provide necessary permits for the construction of the wetlands area. The permitting process is under way.

A paved multi-use trail with boardwalks over wet areas will allow visitors to enjoy the wetlands area. Benches along the way will provide a place to sit to enjoy the natural setting. Plans include the addition of informational signs to describe the many features of the park including the more than 200 different types of plants. A botanist’s dream, the plantings will include blue flag iris, monkey flower, arrowhead, yellow water lily, sky blue aster, early sunflower, prairie blazing star, black-eyed susan, pale purple coneflower and milkweed, just to name a few, according to Ron Londre, ecologist, of Graef-USA, the engineering firm that provided the landscape architectural design for the wetlands park.

The milkweed is critical to the development of Monarch butterflies which are attracted to most species of the milkweed plant. The butterflies use the milkweed plant to lay their eggs. As the tiny caterpillars begin to hatch, they walk along the milkweed and use it as their only source of food and nutrition. After 14 days of eating the milkweed plant, the caterpillars are ready to form a cocoon so they can begin the transformation into a beautiful Monarch butterfly.

Environmental considerations are not exclusive to the wetlands area in DTS. Developers have included the use of pervious pavers for several streets in the development as well as parking lots for the apartments and the Meijer grocery store. The pavers qualify as components of storm-water management, acting as filters to remove total suspended solids – debris that runs off paved areas. The use of the pavers eliminated the need for a fourth retention pond.

Pervious pavement allows percolation or infiltration of storm water through the surface into the soil below where the water is naturally filtered and pollutants are removed. In contrast normal pavement is an impervious surface that sheds rainfall and associated surface pollutants forcing the water to run off paved surfaces directly into nearby storm drains and then into streams and lakes.

Bidding for the construction of the wetlands area will begin in late June. When construction begins, we’ll provide a detailed update on how the work will be completed to ensure that invasive species are removed while not disturbing frogs and other amphibians that inhabit the area.

When completed, in addition to the turtles, butterflies, birds and amphibians, the DTS wetlands park will be enjoyed by the public as well as the people who live, work and shop in the Drexel Town Square.