Five years ago, a housing develoment company needed to prepare a stormwater management plan and design best management practices (BMP) for stormwater management at historic Fort Sheridan. The military base, situated on bluffs overlooking the shores of Lake Michigan in the northern Chicago suburb of Highland Park, was in the midst of transformation from a U.S. Army complex to a residential community.
The restoration was demanded because of the extreme degradation of the ravines that separated property lines and empty into Lake Michigan. Severe down-cutting (extreme erosion due to increased water volume) of the ravine channel floors caused major bank destabilization along the walls of the ravines.
The BMPs emphasized ecological restoration practices for severely eroded bluffs along the shoreline and alternative stormwater management that focused on water quality.
The stormwater management plan also included cost-saving strategies that reduced engineering, long-term management expenses for the entire project site, and also provided marketing benefits to improve the economics of site redevelopment. Preservation, restoration, and perpetuation were recurring themes in this conservation development. Eroding ravine sideslopes were cleared of invasive and non-native woody species, rebuilt with log terraces, and revegetated with native species for soil stabilization.
The project was also designed to conduct ecological restoration and land-management programs and to negotiate environmental permits for the project.
A design-build team hired by the home builder was called upon to correct the problems within the ravines. The channel floors were raised with clay to reestablish the floodplain. The channel was then armored with rock (Photos 1, 3), and grade-control structures for the elevation drops were used along the ravine walls.
Gabion baskets (rectangular, mesh baskets that are filled with stone—see Photos 4, 5, 6) with crib walls were used to repair the severe wall erosion. Geogrids (polymer-coated fibers that are used to reinforce earth-fill slope) were also used on the slopes to re-establish and stabilize the ravine walls (Photo 2).
Finally, chevron drains (a drainage tool that allows water to re-enter the soil without runoff) were implemented to relieve slopes with excess moisture and hidden drainage issues.
Fort Sheridan is developing into a unique neighborhood in that it was originally a military base. The base was officially closed in May 1993. Since then, the area has transitioned into a residential neighborhood and that transition had to be made carefully.
Some buildings were torn down to create more open space, thus many of those materials required disposal. The companies involved in the project were able to recycle approximately 700 tons of rock from the foundations of demolished buildings by breaking it down and using it to armor the channel they were restoring. In addition, approximately 2,000 ft. of telephone poles were recycled by using them to help stabilize the ravine walls (Photos 5, 6).
Throughout this project, which started in 2002 and was completed at the end of November 2006, all native-plant species were used. The integrity of the ravine areas was fully restored and the amount of sediment entering Lake Michigan through the ravines is considerably reduced (Photo 7).
Although the restoration is complete, a five-year maintenance program commenced this spring to ensure the continued success of the project.