Water Quality & Sediment¶
St. Louis River Estuary — Area of Concern¶
The Port of Duluth-Superior operates within the St. Louis River estuary, the largest freshwater estuary in North America and one of 43 EPA-designated Great Lakes Areas of Concern (AOCs) — contaminated sites requiring remediation before delisting.
The estuary has been an AOC since 1987, reflecting decades of industrial pollution from coking plants, steel mills, paper mills, and port operations. Port activities intersect directly with AOC remediation goals through vessel wake effects, ballast water discharge, stormwater runoff, and atmospheric deposition of PM2.5 and nitrogen compounds.
Data Sources¶
| Source | Publisher | Data Provided | Access |
|---|---|---|---|
| ECHO / NPDES | EPA | Facility discharge permits, compliance status, violations | echo.epa.gov |
| Impaired Waters List | MPCA | 303(d) listings for St. Louis River and tributaries | mpca.state.mn.us |
| AOC Data | EPA / MPCA / WI DNR | Management actions, Beneficial Use Impairments, remediation status | epa.gov/great-lakes-aocs |
| Superfund Site Profiles | EPA | Contamination extent, cleanup progress, five-year reviews | epa.gov/superfund |
| Dredging Reports | USACE St. Paul District | Maintenance dredging volumes, sediment disposal, navigation channel status | mvp.usace.army.mil |
| WLSSD Reports | WLSSD | Wastewater treatment performance, effluent quality | wlssd.com |
| Habitat Assessments | MN DNR | Fish and wildlife habitat quality within estuary | dnr.state.mn.us |
| Collaborative Research | Great Waters Research Collaborative | Microplastics, emerging contaminants in Lake Superior basin | Academic partners |
Superfund Sites¶
Two Superfund sites within the port area represent legacy contamination that predates but interacts with current port operations:
SLRIDT (St. Louis River/Interlake/Duluth & Iron Range Tar)¶
- Size: 255 acres
- Primary contaminants: PAHs (polycyclic aromatic hydrocarbons) from historic coking operations
- Status: Active remediation
- Concern: Vessel traffic wake effects can disturb remediated shoreline sediments; dredging operations must avoid re-suspending contaminated material
U.S. Steel Superfund Site¶
- Primary contaminants: Heavy metals, industrial waste from steel manufacturing
- Status: Active remediation with long-term monitoring
- Restoration: The $8.2 million Kingsbury Bay restoration (EPA-funded) is restoring habitat within the AOC boundary adjacent to the U.S. Steel site
Port Operations and Superfund
Vessel traffic within the port area creates wake effects that can disturb remediated shoreline areas. Navigation channel dredging must be coordinated with Superfund cleanup timelines to avoid re-suspending contaminated sediments. USACE dredging permits require consultation with EPA Superfund program managers.
Analytical Outputs¶
1. NPDES Compliance Scorecard¶
Assessment of all active NPDES (Clean Water Act) discharge permits for port-area facilities. The port area includes 23 permitted facilities with various discharge, stormwater, and air permits. Key facilities:
| Facility | Permit Types | 5-Year Violations | Current Status |
|---|---|---|---|
| Duluth Seaway Port Authority | Air, Stormwater | 0 | In Compliance |
| MERC Coal Terminal | Air, NPDES, RCRA | 3 | Closure Pending (June 30, 2026) |
| Murphy Oil Refinery | Air, NPDES, RCRA, TRI | 2 | In Compliance |
| BNSF Superior Yard | Stormwater, RCRA | 1 | In Compliance |
| US Steel Superfund Site | CERCLA, RCRA | 0 | Under Remediation |
2. Sediment Contamination Mapping¶
Spatial analysis of contaminated sediment areas within the port boundary, overlaid with navigation channels and dredging zones. The goal is to identify areas where routine port operations (dredging, vessel traffic, terminal construction) risk disturbing contaminated sediments.
3. AOC Delisting Progress Tracker¶
80+ Management Actions Required
The St. Louis River AOC has over 80 management actions that must be completed before the AOC can be delisted. These span habitat restoration, sediment remediation, water quality improvement, and institutional controls. Port operations intersect with multiple management actions, particularly those related to sediment quality and habitat protection.
The AOC delisting process tracks Beneficial Use Impairments (BUIs) — specific environmental conditions that must be remediated. Port-relevant BUIs include:
- Degradation of benthos
- Restrictions on dredging activities
- Loss of fish and wildlife habitat
- Degradation of aesthetics
- Restrictions on fish consumption
4. Ballast Water Risk Profile¶
Great Lakes vessels carry ballast water between ports, creating a vector for invasive species transfer. While the Great Lakes shipping fleet operates primarily within the Great Lakes system (reducing transoceanic invasion risk), inter-lake ballast water exchange can redistribute established invasive species.
The St. Louis River estuary has documented populations of multiple invasive species, and ongoing monitoring by the Great Waters Research Collaborative tracks emerging threats including microplastics and per- and polyfluoroalkyl substances (PFAS).
WLSSD and Regional Water Infrastructure¶
The Western Lake Superior Sanitary District (WLSSD) provides regional wastewater treatment for both Duluth and Superior. Port-area stormwater runoff — including potential coal dust, petroleum residues, and industrial chemicals — flows through the combined stormwater/sanitary system during wet weather events. WLSSD's treatment performance data provides an indirect measure of port-area water quality pressures.
Last updated: April 2026
Data sources: EPA ECHO/NPDES, EPA Superfund, MPCA Impaired Waters, USACE St. Paul District, WLSSD, MN DNR, Great Waters Research Collaborative