Formatted Title:

Implementing a Complex, Large-Scale Sediment Remediation Project with Multiple Disciplines

Background/Objectives:

The three‑year Spirit Lake sediment remediation project consisted of multiple phases of year-round remedial construction to restore approximately 138 acres in the St. Louis River Great Lakes Area of Concern (AOC) near Duluth, Minnesota. Spirit Lake sediments—along with adjacent wetlands and upland areas—were impacted by former industrial operations adjacent to and upstream of the site. J.F. Brennan Company, in collaboration with the U.S. Environmental Protection Agency Great Lakes National Program Office, U.S. Steel, and EA Engineering, completed the project in 2024.

Approach/Activities:

The project included numerous and interlinking facets of upland, marine, and civil construction activities in addition to large-scale restoration and remediation operations requiring continual coordination.

Construction of two confined disposal facilities for stabilized and hydraulically dredged sediments.
Construction of a meandering stream including installation of root wads for fish habitat.
Marsh excavation of approximately 80,000 cubic yards of impacted sediment during winter by means of ice roads and utilizing standard excavators and haul trucks.
Hydraulic dredging of approximately 190,000 cubic yards of impacted sediment.
Dewatering sediment by means of geotextile tubes and water treatment.
Placement of over 86 acres of subaqueous cap using Brennan’s patented Broadcast Capping System (BCS™) and, in areas with limited draft, open-pipe discharge.
Placement of 5,800 linear feet of shoreline protection using amphibious and railroad equipment.
Installation of a railroad bridge and two at-grade railroad crossings.
Restoration including seeding over 50 upland acres, installation of over 400,000 aquatic plants, and installation of a 2.2-mile pedestrian trail along the St. Louis River.

Results/Lessons Learned:

A proactive, communicative management approach paired with ongoing adaptability and innovation contributed to the success of this project and reinforced the many lessons learned throughout implementation.

Innovation on site was at the forefront of daily operations to combat fluctuating water elevations and difficult-to-access areas. The project team implemented an amphibious excavator and dump truck to complete dredging operations in shallow water, also utilizing an amphibious excavator to place the subaqueous cap in nearshore areas. With difficult access along the river, a fleet of railroad equipment was used to place shoreline protection materials including fabric and riprap.

Consistent subcontractor culture formed a unified contractor team. Adaptable subcontractors, well-matched to the project teams’ culture, supported and facilitated project goals. Brennan previously executed work with the three selected subcontractors due to their excellence in their field, high-quality performance of work, and comparable company cultures.
Contractor flexibility through extended and year-round construction proved critical to ongoing operations. Work continued through the global pause due to the COVID‑19 pandemic as well as extreme weather conditions (e.g., cold, record snowfall, flooding, seiche events and drought conditions). Continual and cooperative review of options and alternatives was necessary to drive forward project progress.
Survey and quality control supplied robust validation through multiple means and methods. Topographic, single-beam hydrographic, side scans, total station, and drone surveys collected data through all aspects of work. Most of the engineered caps consisted of two to three layers of different materials; thus, survey data were key to verify layer thickness and placement accuracy.

Erik Papenfus

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Implementing a Complex, Large-Scale Sediment Remediation Project with Multiple Disciplines