Ecological Vision Drives Post Superfund Cleanup River Restoration

The West Branch of the DuPage River is a second order stream in Northeastern Illinois. At the Warrenville Grove Dam, it drains 90.4 sq. mi., which includes 18.4 sq. mi. drained by its largest first order Tributary Kress Creek. Waterborne deposition of inert — but radioactive — mine tailings containing low-level Thorium, (²³²Th) throughout a 7.5-mile reach of the river complex, set the stage for a massive cleanup under the CERCLA-Superfund program. In the immediate aftermath of the cleanup was a stream system pocked with excavations and construction operations that severely damaged both banks and the stream bed. More than half of the affected land and 60% of the shoreline is owned by the Forest Preserve District of DuPage County, who have been actively managing their land for restoration to ecologically balanced conditions, and while the cleanup is a short term setback, the restoration of the land after the cleanup was viewed as an opportunity to further overall restoration goals. The immediate functions of the steam system — to move water and sediment — had to be reestablished as quickly as possible and in a manner that promoted dynamic stability. At the same time, opportunities to mitigate for the loss of aquatic habitat and wetlands had to be found and implemented. These sometimes conflicting imperatives have been balanced to provide a post-cleanup restoration that is expected to further enhance the biodiversity and functions of the aquatic, wetland, and upland communities. The entire affected stream reach was characterized both quantitatively and qualitatively for the presence of aquatic structure, function, and habitat, utilizing the IEPA stream assessment methodology (IEPA, 1994) to establish a baseline against which the long-term and short-term restoration effects can be compared. Quantitative measurements of water quality were also taken and monitored during the cleanup. Prior to excavation related to the cleanup, fish and mussels were collected, surveyed, and relocated to other stream reaches not affected by the cleanup, which produced a baseline census of the pre-cleanup aquatic community. Post-excavation restoration design emphasized the establishment of in-stream structure and a diversity of flow conditions and regimes to provide the broadest cross-section of habitats possible. Existing pool-riffle complexes were identified and restored as a part of the post cleanup activities, while a variety of in-stream structure was added, including bendway weirs, vortex weirs, and selective addition of boulders. Short-term habitat losses, such as in-stream woody debris and undercut banks were mitigated to jumpstart the return of the biotic community. Commitments for maintenance and monitoring under CERCLA afford the opportunity to assess the effectiveness of the restoration over a longer term, and the continued post restoration management activities of the Forest Preserve District cast a vision for the recovery of a degraded urban stream corridor.