EWN Publications

Evaluating restoration success in a Great Lakes embayment: A case studyfor addressing beneficial use impairments

Brett A. Hayhurst, Kristen M. Buscaglia, Karen G. Keil, Joseph Kreitinger, and Dan Breneman
August 18, 2023

About This Publication

Aquatic habitats within the St. Louis River estuary were impacted when developing the Duluth-Superior Harbor (MN/WI USA) and through decades of unregulated industrial and municipal discharge. An effort to remediate and restore sediment quality in the harbor began by implementing projects designed to address Beneficial Use Impairments (BUI) identified in this Area of Concern. Habitat restoration in the 21st Avenue West project site was implemented to improve overall aquatic community health and address a degradation of benthos BUI. Restoration objectives focused on creating more complex bathymetric surfaces and mitigating contaminant exposure by capping with clean dredged material. Before and after construction, samples were collected to assess the benthic community within 21st Avenue West compared to results from least-impaired, reference locations. A scaled trimetric index (s-TMI), scored between 0 and 1, was used to track an impaired benthic community before and after construction. A median s-TMI value for 21st Avenue West prior to construction (value = 0.51) improved following restoration (site median = 0.65), reaching a site-wide value that was not significantly different from the least impaired removal target (reference median = 0.68, when calculated from pooled reference data). Results from post construction sample collections at 21st Avenue West suggest macroinvertebrate community index scores increased by more than 10% two years following construction. These results indicate that the 21st Avenue West habitat restoration effort successfully reached a degradation of benthos BUI goal and demonstrates that dredge material is a cost-effective alternative for construction.

Research Projects

This EWN Action Project identifies and develops low-cost, shallow-water dredged material placement methods, utilizing both engineered and natural processes. These methods maximize the habitat value of the dredged mate...