21st Avenue West
A Pilot Study for Beneficial Use of Dredged Material for Addressing Degraded Aquatic Habitat and Benthic Communities
Partnership
This work was conducted as technical support to the Minnesota Pollution Control Agency (MPCA) by the US Army Corps of Engineers (USACE)–Detroit District, US Army Engineer Research and Development Center (ERDC) and Dredging Operations Technical Support (DOTS) program. Support was provided under a partnership agreement for technical, planning and engineering assistance in the St. Louis River Area of Concern with funding from the US Environmental Protection Agency Great Lakes Restoration Initiative (GLRI), the Minnesota Clean Water Land and Legacy Amendment, and the USACE Engineering With Nature® (EWN®) program.
The Great Lakes
Since 1972, the Laurentian Great Lakes have been protected by one of the most successful binational water quality agreements in the world–the Great Lakes Water Quality Agreement between the United States and Canada. As part of that Agreement, the United States and Canada have committed to protecting, enhancing, and restoring ecosystem health in these lakes and maintaining it for future generations. The Great Lakes contain over 20% of the world's surface fresh water, providing drinking water to over 40 million people, numerous recreational opportunities, and billions of dollars in economic benefits across the region. The 1987 amendment to the Great Lakes Water Quality Agreement identified 43 Areas of Concern (AOC) around the Great Lakes, which are “geographic areas designated by the Parties where significant impairment of beneficial uses has occurred as a result of human activities at the local level." The Great Lakes Restoration Initiative was authorized in 2009 to accelerate efforts to protect and restore the Great Lakes ecosystem. Federal, Tribal, State, and local partners are all involved in GLRI research and restoration efforts, including addressing AOCs.
Graphic from https://www.epa.gov/great-lakes-aocs/list-great-lakes-aocs , Accessed on October 2022.
The Great Lakes Regional Collaboration Strategy provided the foundation for the GLRI and identified a Great Lakes Interagency Task Force and Regional Working Group who, along with a Great Lakes Advisory Board , selects the best combination of programs and projects to implement the GLRI Action Plan . The USACE (representing the US Department of the Army) is one of the 15 federal agencies involved in Regional Working Group activities supporting the GLRI. Each federal agency works within its own authority to foster the goals of the GLRI Action Plan. The authority and ability of the USACE to manage sediments dredged from federally maintained navigation channels has been a powerful tool in the ecosystem restoration toolbox at some of the Great Lakes AOCs. These sediments have become cleaner in recent decades and are often suitable for beneficial uses, including restoration of aquatic habitat.
Lake Superior
Lake Superior lies between Canada and the United States and drains into Lake Huron to its east. At 406 meters deep, Lake Superior is both the largest and deepest Great Lake.
Lake Superior lies between Canada and the United States and drains into Lake Huron to its east. At 406 meters deep, Lake Superior is both the largest and deepest Great Lake.
Furthest Western Point–Duluth Harbor
The St. Louis River estuary is at the most western point of Lake Superior and is the largest freshwater estuary in the Great Lakes. Within the lower St. Louis River estuary, the Duluth Harbor is one of the largest ports in North America, containing a massive multimodal shipping hub developed in the early 1800s. Early industry contaminated sediment throughout the estuary, which degraded habitat quality. In 1988, the St. Louis River estuary, including the Duluth-Superior Harbor, was designated as an AOC.
Photo from USACE–Duluth-Superior Harbor.
Video from Duluth Harbor Canal Cam.
St. Louis River
The St. Louis River AOC originally had nine Beneficial Use Impairments (BUIs), three of which are being addressed by completing sediment remediation and habitat restoration projects. They are the following:
- Degradation of benthos (macroinvertebrates),
- Restrictions on dredging, and
- Loss of fish and wildlife habitat
Over a dozen active remediation and habitat restoration projects are planned or ongoing in the AOC, with the 21st Avenue West Habitat Restoration Project introduced as a pilot study to establish environmental objectives, inform design decisions and construction specifications, and evaluate project performance to evaluate the beneficial use of dredged material to improve benthic conditions.
- Yellow lines represent the Navigation Channel footprint where clean dredge material are removed (map on right).
- Orange areas with inset dots are construction footprints where clean dredged material is applied for habitat enhancement.
Graphic from Minnesota Pollution Control Agency, 2022.
21st Avenue Embayment
The 21st Avenue West Embayment site is located in St. Louis Bay, a section of the St. Louis River estuary, that contains some of the most concentrated industrialized activity in the Duluth-Superior Harbor. The 21st Avenue Habitat Restoration Project was implemented using a new approach in which the evaluation of environmental metrics representing resource management goals were incorporated into the design document as engineering specifications for dredged material placement (USACE 2015).
Photo from Kristen Buscaglia–Bridge near 21st Avenue West Embayment.
The 21st Avenue project was featured in the first Engineering With Nature Atlas, which provides further information regarding;
Download the Engineering With Nature: An Atlas, Volume 1 . to view more information regarding the Duluth 21st Avenue West Demonstration Project (page 76).
Habitat Restoration Design
Plans to restore 21st Ave began with a focus on BUI removal by incorporating environmental targets as design criteria and establishing engineering specifications that would cost-effectively use material dredged from the federal navigation channel for habitat construction. Restoring 21st Ave involved both a pilot study (first phase 2013–2015) and a construction phase (2016–2018) to incrementally utilize annual navigation operations and maintenance authority and funding for dredged material management.
Graphic from USACE–Showing shoal design features and placement within the Embayment.
A Design Documentation Report (DDR) was completed to capture decisions focusing on construction parameters, feasibility, cost, habitat objectives, and long-term management responsibilities (USACE 2015). In this design document, modeled site conditions were assessed using a suite of environmental metrics that describe the relative improvements expected when comparing restoration alternatives. Ultimately, a desired environmental outcome was incorporated as design criteria, ensuring that areas with high probability of improving conditions were prioritized for construction (MPCA and MNDNR 2015). This six-year construction effort utilized over 783,000 cubic yards of navigational dredged material to complete the approved habitat restoration designs.
Photos from Kristen Buscaglia–Processing dredged material for beneficial use.
Evaluating Habitat Restoration
To establish a consistent, cost-effective evaluation approach, an effort was launched to develop numeric standards for benthic macroinvertebrate communities in the estuary, resulting in a scaled Trimetric Macroinvertebrate Index (s-TMI). The s-TMI consists of three metrics selected for their sensitivity to disturbance (1) taxa richness; (2) percent abundance of non-oligochaete; and (3) percent abundance of the orders Ephemeroptera, Trichoptera, and Odonata.
Graphic From Brett Hayhurst–Macroinvertebrate images.
The s-TMI is a measure of macroinvertebrate community quality at varying water depths and is used to compare habitat restoration site conditions with reference locations within geographic zones throughout the estuary. Results from post construction sample collections at 21st Avenue West project site suggest macroinvertebrate community index scores improved by more than 10% two years following dredged material placement. Coupled with an overall s-TMI site value is no longer significantly different than the least-impaired target, the 21st Avenue West project site represents a successful application of dredged material for habitat restoration that should be included in an eventual degradation of benthos BUI removal recommendation for the St. Louis River AOC.
Photo from Kristen Buscaglia–St. Louis River near Spirit Lake.
Coastal wetlands serve a myriad of important functions in the Great Lakes, including maintaining water quality, supporting biological diversity of native species, providing recreational opportunities (sport fishing, waterfowl hunting, kayaking, and bird watching), protecting shorelines from storm damage and flooding, and providing a traditional food source (wild rice) for Tribal communities. The Great Lakes have lost at least half of the approximately one million acres of coastal wetlands thought to exist over a century ago (epa.gov, 2022). Creating, restoring, and protecting coastal wetlands is an important component of the current Great Lakes Restoration Initiative (GLRI) Action Plan (2020–2024).
In this project, sediments dredged from the nearby federal navigation channel were used beneficially to restore wetlands (sequestering contaminants and improving benthic habitat, which in turn improves fishing and birding opportunities), instead of simply removing the sediments for disposal outside of the littoral zone. By constructing this project using funds slated for operation and maintenance of the Duluth-Superior Harbor federal navigation channel, this USACE EWN® project provided economic, social, and environmental benefits while supporting navigation infrastructure.
References and Credits
MPCA and MNDNR. 2015. St. Louis River Area of Concern Quality Assurance Program Plan for Minnesota Based Projects. Minnesota Pollution Control Agency and Minnesota Department of Natural Resources.
USACE (U.S. Army Corps of Engineers/Engineer Research and Development Center). 2015. Sediment Transport Modeling for the St. Louis River estuary- 21st Ave West Shoals and Islands Designs. Environmental and Coastal and Hydraulics Laboratories.
USEPA website. https://www.epa.gov/great-lakes-monitoring/why-monitoring-great-lakes-coastal-wetlands-important. Accessed November, 2022.
Special thanks to Dan Breneman with Minnesota Pollution Control Agency, the Wisconsin Department of Natural Resources and the teams of individuals at the Federal, Tribes, State, and local level that make this work possible.
Funding for this project includes a USACE and USEPA partnership agreement with the MPCA through Great Lakes Restoration Initiative awards and the Minnesota Legislative Clean Water Legacy funds. Additional funding support came from USACE DOTS and EWN® programs.
All photographs by the U.S. Army Corp of Engineers unless otherwise noted.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.
Authors: Brett Hayhurst (ERDC), Kristen Buscaglia (LRB), Dan Breneman (MPCA), and Karen Keil (ERDC), January 2023.
