At Munger Landing in Duluth, Minnesota, Brennan led a large-scale environmental remediation project upstream from Lake Superior. The team removed historical contamination across more than 34 acres of the St. Louis River. This multi-year project addressed PCBs, mercury, dioxins, and furans. Brennan used precision hydraulic dredging, sediment dewatering, water treatment, and strategic placement of clean sand and habitat materials.
Brennan worked closely with GEI Consultants throughout the project. The U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, Minnesota, and Wisconsin provided project oversight. Together, the team restored the riverbed and supported long-term environmental health.
“The scale and scope of this project demanded constant coordination, innovation, and respect for the environment.”
— Casey Evenson, Project Manager
Mobilization and Multi-State Coordination
Brennan mobilized equipment and materials at Munger Landing and Hallett Dock 7. Three dredges connected through a 2.5-mile pipeline transported sediment to the onshore dewatering field.
The project required coordination across two states, multiple federal agencies, and the U.S. Army Corps of Engineers.
“This project required aligning with the regulatory frameworks of two states, federal agencies, and the Army Corps. Transparency and collaboration were key to our success.”
— Amber Wilson, Environmental Compliance Manager, Brennan
Dredging and Debris Management
Brennan removed contaminated sediment from shallow and deep areas using targeted hydraulic dredging. Crews navigated debris-filled zones, shallow water, wood accumulation, and tight working corridors. The team pumped sediment to geotextile tubes for dewatering. On-site treatment systems separated solids and treated the water.
Water Treatment Excellence
The dewatering field separated water from dredged sediment. Brennan processed the water through a multi-stage treatment system. The treatment plant used multimedia filtration and granular activated carbon (GAC) to remove contaminants. The team collected samples throughout treatment to verify performance and maintain regulatory compliance.
Capping and Habitat Restoration
After dredging, Brennan placed a clean sand cap across the entire project footprint. The cap typically measured 6 to 12 inches thick. It isolated remaining contaminants and restored habitat.
In selected areas, Brennan installed a bio-medium cap using material from nearby Perch Lake. Crews installed more than 16,000 feet of spreader piping. Brennan’s patented Broadcast Capping System evenly distributed cap material across sensitive aquatic habitats.
Environmental Impact and Legacy
The project met every performance metric despite tight construction parameters and some of Brennan’s strictest turbidity requirements. The restored riverbed will benefit aquatic life, local ecosystems, and community recreation for generations.
“This project helps restore the river to the way it should be—especially in a beautiful community like Duluth.”
— Amber Wilson, Brennan
The U.S. Environmental Protection Agency, the Minnesota Pollution Control Agency, the Wisconsin Department of Natural Resources, and industry partners funded this project. Contract #68HE0521D0002.
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