Transforming an impaired lake into a healthy, meandering stream that naturally goes with the flow took years of watershed planning and patience. It has become the single largest, most complex land and water management project our ecologists and planners have ever tackled.
From the trail overlooks, you'll see the impressive results of this major ecological restoration effort to improve water quality and reestablish the native landscapes of Ethel's Woods. It took 12 years to complete. Many discussions by our ecologists and land planners at the start of the project focused on the preserve's serpentine-shaped lake.
Historically, North Mill Creek meandered through what is now Ethel's Woods. In 1957, the property owner dammed the creek by building a 600-foot-long earthen dam to create a 58-acre man-made lake, which was named after the family––Rasmussen Lake.
When the Lake County Forest Preserves acquired the land in 2001, staff conducted aquatic surveys of the lake and studied restoration options with an advisory committee of scientists and permitting agencies. At first glance, Rasmussen Lake seemed possible for recreation use, but beneath the surface were real problems. The shallow lake, fed by North Mill Creek, was in bad shape. The banks of Rasmussen Lake were eroded with steep drop-offs. The basin was a mucky mess, packed with several feet of thick, pudding-like sediment built up behind the dam. Dams are barriers to nature's cleansing process. They hold and store pollutants instead of cleaning them. In terms of overall water quality and clarity, the lake was in poor health, ranking next to last among the 162 lakes monitored by the Lake County Health Department.
Faced with options on how best to proceed––do nothing, dredge the lake, or restore the stream––the Forest Preserve Board chose nature's way. In 2007, they made the decision to restore the original flow of North Mill Creek through Ethel's Woods. And, they approved measures to remove the dam and slowly drain the lake to allow a new stream channel and floodplain to be constructed, ultimately returning the landscape to a more natural state. A $1.5 million Clean Water Act grant from the Illinois Environmental Protection Agency helped fund the restoration.
Along the eastern edge of this preserve are 170 acres of century-old bur oak, white oak, shagbark hickory and black walnut trees. Scattered throughout the preserve's oak-hickory woodlands are small, isolated forest ponds that hold water in the spring and early fall. These ponds, along with two Advanced Identification (ADID) wetlands bordering the high-quality Old Mill Creek stream corridor, provide valuable wildlife habitat and food sources for a variety of birds, mammals and reptiles.
Read more about the evolution of Ethel's Woods in the winter 2018 issue of our Horizons magazine.