The U.S. Army Corps of Engineers will be spending millions of dollars in the next couple of years to remove invasive species, encourage native plant growth and replenish the underground water source for a patch of extremely rare habitat in Lockport Prairie Nature Preserve.
Lockport Prairie features wet and wet-mesic dolomite prairie, which are among the most critically imperiled natural communities on Earth. More than half of the high quality wet dolomite prairie in the world is located at the preserve, which is home to endangered and threatened species.
The Army Corps project falls under Section 206 of the Water Resources Development Act, which protects aquatic resources in the United States. The project’s goal is to restore the natural habitat and critical groundwater relationship between the Forest Preserve's Prairie Bluff Preserve in Crest Hill and Lockport Prairie in Lockport Township. As groundwater from Prairie Bluff moves slowly toward the Des Plaines River, it flows into Lockport Prairie where it seeps from a bluff or percolates above ground creating habitat for a diversity of plants and creatures.
The Army Corps released a bid packet for the project on November 17 and bids will be opened December 19. Restoration work could begin this winter and it will span an estimated five years. The project will total $2.5 million initially, but there could be additional appropriations in the coming years to fund more restoration options at Prairie Bluff.
"The Forest Preserve and Army Corps of Engineers have been working together for over a decade to develop a strategy to preserve and enhance Lockport Prairie," said Ralph Schultz, the Forest Preserve's chief operating officer. "We're excited this project is moving into its next phase with a significant investment by the Corps in preserving the future of one of Will County's natural wonders."
Initial work will involve invasive species removal at Lockport Prairie and implementation of erosion control measures. If future options are funded, work also will be done to disable agricultural drain tiles that currently disrupt the natural flow of groundwater at Prairie Bluff.
Lockport Prairie inhabitants include the federally endangered Hine's emerald dragonfly, leafy prairie clover and lakeside daisy; the state-endangered golden corydalis and spotted turtle; and the state-threatened stiff sandwort and Blanding's turtle.
Leafy prairie clover was thought to be extinct until it was discovered at Lockport Prairie in 1974. And the lakeside daisy's population was wiped out in the area in the 1970s, but it began a comeback after being reintroduced in the mid-1980s to Lockport Prairie.
Lockport Prairie also is home to more than 20 ant species. "The assemblage of conservation ants at Lockport Prairie is quite dissimilar to any other yet recorded in the Chicago region," according to a project feasibility study completed by the Army Corps in 2015.
Restoration work is needed at the site because human activity has disrupted the flow of groundwater from Prairie Bluff to Lockport Prairie. Disruptions include the excavation of the I&M Canal, farming, quarrying, and the addition of parking lots, roads and other paved surfaces. Changes in the landscape and storm water management also have affected the natural amount of groundwater that feeds the preserve.
After managing the site for nearly three decades under a lease agreement, the Forest Preserve acquired Lockport Prairie from the Metropolitan Water Reclamation District of Greater Chicago in 2011. That same year, the Forest Preserve used a grant from the Illinois Department of Community and Economic Opportunity to create a groundwater infiltration basin at the eastern end of Prairie Bluff. A second basin was installed, along with a public access point and a trail, at Prairie Bluff in 2012. The basins hold back groundwater so it infiltrates the soil and flows slowly to Lockport Prairie.
The Forest Preserve has contributed $320,000 in past years for surveys and studies needed for the Army Corps' project. And the real estate, or land value, of the preserves will satisfy the District's required 35 percent contribution for project implementation.
According to the 2015 feasibility study, the variety of native plants in Lockport Prairie has been declining since 2002 and invasive species that prefer drier conditions have been taking over the site.
"Other signs of hydrologic disturbance have also been observed, most notably the death of several of the state-listed spotted turtles due to the drawdown of ground water while they hibernated," the study stated.
The Hine's emerald dragonfly's reproductive output has dropped due to declining habitat, and the leafy prairie clover's population is waning. Both species depend on the wetland habitat found within dolomite prairies.
The Army Corps' feasibility study explains how dolomite prairie was formed at Lockport Prairie thousands of years ago when glaciers north and east of the Kankakee area began to melt creating lakes and flooding.
"This great flood scoured the old river valley down to the Niagaran dolomite bedrock in the study area," the study reported. "This action peeled off large chunks of dolomite, and left behind bars of rock and gravel in the floodplain that are now dolomite prairie. The water's force also deposited a steep layer of sand, gravel, and rock … that now acts as a conduit for the ground water that discharges into the prairie from along the bluff."
Without restoration work, the site will continue to get drier, which would reduce habitat for wetland-dependent insects, plants and animals. That means the Hine's emerald dragonfly wouldn't have the rivulets it needs to survive and reproduce, more turtles might perish, and the threatened plant species could disappear from the area once again.
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