Where do fish go when you drain a lake?
Relocating fish part of plan to restore 60-year-old landscape near Antioch
To reach Rasmussen Lake near Antioch, a four-wheel-drive vehicle is best to navigate a rutted dirt path through an open field that ends after about a half mile in overgrowth near the water.
Great blue herons glide about and the stand of dense forest ringing the shoreline is reminiscent of the Wisconsin north woods. But all is not what it appears to be on this isolated, hidden lake in the midst of a $6.1 million transition.
"It's kind of a biological sinkhole," says Leslie Berns, manager of landscape ecology for the Lake County Forest Preserve District. Berns is overseeing a project to drain the 53-acre lake within the Ethel's Woods Forest Preserve and restore about a mile of North Mill Creek to the way it was about 60 years ago.
But as the water slowly recedes, there is a need to ensure the number of fish is in line with the size of the oxygen-deprived lake. Mussels, too, are exposed as the footprint shrinks.
Fisheries biologists from the Illinois Department of Natural Resources, at the request of the forest district, arrived this week to collect a catch for relocation.
"We're here to save the fish," said Frank Jakubicek, district fisheries biologist for the state agency. "You're utilizing a resource that may go to waste."
Carp, yellow bass and green sunfish are more tolerant of low oxygen levels and were not collected. But about 200 fish of 13 species, including large mouth bass, blue gills, golden shiner, crappie and pumpkinseed, were caught to be relocated to Sterling Lake in the Van Patten Woods Forest Preserve near Wadsworth.
Jakubicek explained that deeper water, 10 feet or more, is more desirable for sport fish. Rasmussen is now about 7 feet deep.
In a typical lake, the agency catches about 60 large mouth bass an hour, but about 20 to 25 an hour were caught Tuesday. A mild electric shock is used to stun fish so they float to the surface where they can be scooped up by crews.
"We got a lot of fish today, but they're all little," Jakubicek said. When the restoration is complete, various species of fish from the Des Plaines River are expected to migrate to the area, he said.
"That's what we're trying to do," Berns responded.
Because they don't move very fast and don't retreat with the water like fish do, mussels aren't relocated until the lake level drops and they are exposed. That was to have been done this week, but the lake level couldn't be lowered as planned because of recent rain that swelled the creek.
Rasmussen Lake is listed as impaired by the Illinois Environmental Protection Agency, meaning there is little ecological or recreational value, Berns said. The intent of the North Mill Creek Channel Restoration project is to improve the water quality and attract new species .
But to keep the sediment from migrating and creating issues downstream, crews can't simply pull the plug and let the water drain.
"We're going to do it very slowly and let the sediment dry," Berns said. Meanwhile, the stream will carve a path through the sediment.
Rasmussen Lake was created in the mid-1950s by a previous owner who built an earthen dam 20 feet deep and 600 feet long with a concrete spillway to contain North Mill Creek. Since then, the lake has filled with an estimated 10 feet of pollutant trapping sediment and the banks have severely eroded.
The sentiment among district officials was different in 2001 when what is now the Ethel's Woods Forest Preserve east of Route 45 and south of Route 173 was acquired.
"When we bought the land, a lot of commissioners were excited, 'What a beautiful lake,'" recalled Jim Anderson, the district's director of natural resources. "It became really clear, really quick the lake was in very bad shape."
Dredging the lake and making the shoreline safe and accessible for public recreation was deemed too expensive. By 2007, forest district officials decided to drain it and restore the creek.
After an extensive permit review process, work began last fall with the installation of a coffer dam -- a sheet metal structure built into the earthen dam. To control the lake water level, 15-inch-high rectangular concrete blocks called stop logs have been stacked atop each other. An excavator is used to remove one stop log at a time, allowing the lake water over about 18 hours to flow downstream through a box culvert.
The first stop log was removed in December, but it's a slow process as the district does not want any sediment to escape downstream.
"We always anticipated it would take 18 months to two years, and we have eight to nine feet to drop lake levels," Berns said. "We want to let the sediment dry out and firm up."
So far, about 6 acres of sediment hae been exposed and a broad, shallow channel is forming in the upper lake basin. In the lower portion, there is a shoreline of 10 to 20 feet of exposed lake bottom.
The first phase of the project will end when the lake is drawn down to a 14-acre wetland, Berns said. Sedges and a diverse variety of wetland plants will be installed and the next step will be to remove the spillway, stabilize the steep slopes of the former lake and reconnect the creek.
"There's about an 8-foot difference between the top of the sediment and the top of the stream bed downstream," she said. "We have to figure out how to breach that without creating a waterfall."
Ethel's Woods is not open to the public, but there are plans to build a tunnel beneath Route 45 and to connect with the adjoining Raven Glen Forest Preserve, said Randy Seebach, the district's director of land planning and preservation.
A parking lot will be built and a trail will take visitors to two overlooks to include exhibits explaining the restoration process, he added. Construction could begin in 2017.