St. Louis River Area of Concern sediment cleanup sites

Link to St, Louis River Area of Concern interactive mapThe Minnesota Pollution Control Agency is working with a number of federal, state and local partners to clean up 10 sites in and around the St. Louis River. The contamination at these sites is the result of a century of industrial and shipping activities in the area that left “legacy pollutants.” The these areas are identified for cleanup as part of the St. Louis River Area of Concern Remedial Action Plan.

All cleanup options for these sites are weighed against four goals:

  • Minimize exposure to sediment contaminants that contribute to fish-consumption advisories.
  • Minimize exposure of aquatic organisms to contaminated sediments.
  • Preserve water depth to enable the current use of the slip.
  • Enhance deep water aquatic habitat where possible.

Why it’s critical to clean up and protect the St. Louis River

The St. Louis River is the largest U.S. tributary to Lake Superior and has a special significance in the region. It is a geographic boundary for Wisconsin and Minnesota, and provides access to Lake Superior which is vital to regional shipping. Development along the waterway during the past 130 years has added to contaminated sediments and caused 73 miles of the St. Louis River to be designated an Area of Concern in the Great Lakes.

The St. Louis River estuary is the second largest of 43 highly-contaminated locations throughout the Great Lakes that were identified by the International Joint Commission for cleanup. Due to decades of uncontrolled pollution before modern pollution laws went into effect, riverbed sediments are contaminated with mercury, dioxins, PCBs, PAHs, and other toxins.

These pollutants have settled out in sediments at the bottom of the St. Louis River estuary and continue to threaten public health, contaminate fish and wildlife, and make waterfronts unusable in Duluth and other communities along Lake Superior. Federal funds now available will accelerate cleanup efforts and help communities fulfill the promise of economic revitalization, increased property values and improved quality of life.

Since the late 1980s, the MPCA and Wisconsin Department of Natural Resources have been collaborating on a plan to delist the St. Louis River Area of Concern. Due to accelerated funding and planning, partners expect this plan to be accomplished by 2025. To achieve this goal, nine Beneficial Use Impairments in the AOC must be removed; many are linked to the presence of sediment contaminants.

Minnesota’s AOC cleanup plan for all 10 sites is now ready, thanks to years of collaborative work by dozens of partner organizations from local, state, tribal, and federal units of government, nongovernmental groups, businesses, research institutions, and community groups. The plan outlines the work needed to restore the water quality and natural resources of the St. Louis River estuary by 2025.

To help implement the plan, Minnesota has secured a partnership with the U.S. Army Corps of Engineers to provide technical, planning, and engineering assistance.

A cleanup remedy, with an estimated $1.6 million cost to complete, has already been selected for the Minnesota Slip. It was the least expensive option, because it moves 2,500 cubic yards of contaminated sediments to the slip’s deeper areas, covers the leveled sediment with a 3-foot cap, and requires no offsite disposal.

Information about the cleanup options that were considered are available in the PDF icon Revised Focused Feasibility Study (tdr-fg16-01).

Slip 3 is a manmade slip in the Duluth Harbor, located within the St. Louis River AOC on Lake Superior. Slip 3 is bordered to the east by the Pier B Resort and Hotel, and to the north and west by a vacant lot owned by the Duluth Economic Development Authority (DEDA) who is currently evaluating a mixed-use commercial residential development plan. Historical releases of contaminants resulted in sediment contaminated with copper, lead, mercury, zinc, polycyclic aromatic hydrocarbons (PAHs), and dioxins. Contaminated sediment is located generally in the northern portion of the 2.75 acre slip.

Information about possible cleanup options is available in the PDF icon Slip 3 final focused feasibility study (tdr-fg17-02).

Slip C is an active shipping slip in the Duluth Harbor basin located at the far northwestern corner of Superior Bay within the inner portion of the Duluth Harbor and is the northernmost slip in a series of slips located on the eastern side of Rice’s Point. Slip C, surrounded by land on three sides, is within the St. Louis River AOC on Lake Superior. Historical releases of contaminants resulted in sediment contaminated with lead, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), mercury, cadmium, copper, zinc and other metals in the 12-acre slip.

Information about possible cleanup options is available in the PDF icon Slip C final focused feasibility study (tdr-fg17-01).

Northland Pier/AGP Slip, an active manmade slip  located in the Duluth Superior-Harbor within the St. Louis River AOC on Lake Superior. Historical releases of contaminants resulted in sediment contaminated with arsenic, cadmium, copper, polycyclic aromatic hydrocarbons (PAHs), lead, polychlorinated biphenyls (PCBs), and zinc generally identified in head of slip in  the southwestern portion of the 8 acre slip.

Information about possible cleanup options is available in the PDF icon AGP/Northland Slip final focused feasibility study (tdr-fg17-04).

Azcon/Duluth Seaway Port Authority (DSPA) Slip, an active manmade slip located in the Duluth Superior-Harbor  within the St. Louis River AOC on Lake Superior. Historical releases of contaminants resulted in sediment contaminated with polycyclic aromatic hydrocarbons (PAHs), arsenic, lead, mercury, zinc, nickel, copper, polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins/dibenzofurans (dioxins). These contaminates were generally identified at the head of the slip and along the northern dock wall in the 6.4 acre slip.

Information about possible cleanup options is available in the PDF icon Azcon/Duluth Seaway Port Authority final focused feasibility study (tdr-fg17-03).

The Ponds behind Erie Pier are two open water ponds surrounded by shallow marsh wetlands, located within the St. Louis River AOC on Lake Superior. A Remedial Investigation in 2015 identified cadmium, chromium, copper, lead, mercury, nickel, zinc, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins/furans as the primary contaminants for the Site. Contaminated sediment was generally identified throughout the 21 acres of ponds.

A feasibility study on cleanup options for this site should be available in 2018.

Munger Landing is a cut-off channel, separated from the current shipping channel by a long, narrow island, and is located directly downstream from the U.S. Steel Superfund site. The sides of the channel are characterized by shallow emergent vegetation areas and small intermittent islands of vegetation with water depths ranging between 1 and 3 feet. The central historical river channel is primarily characterized by a deeper channel with depths ranging from 6 to 10 feet. Historically, the western shore of the site was used for railroad transportation.

Historical maps also indicate that steel mill operations occurred north and south of the western shore of the Munger Landing. Ship building operations occurred in the slips located directly adjacent to the north (downstream). Currently, the west side of the site is used as a boat launch.

A feasibility study on cleanup options for this site should be available in 2018.

Mud Lake West comprises a 39-acre wetland area in the St. Louis River estuary. The majority of the site is marshland with open water located in the center of the lake. A railroad causeway running northeast to southwest acts as a levee separating Mud Lake West from the rest of Mud Lake and the main river channel. The site is approximately 3,750 feet in length and 1,000 feet in width and average water depth is 3.5 feet.

The upland adjacent to the site was used by U.S. Steel for steel mill refuse disposal purposes from 1948-1974. Steel mill slag was placed within the water table at the toe of the main slag impoundment. Currently, Mud Lake West is surrounded by undeveloped or abandoned industrial properties. The railroad causeway is owned by the city of Duluth, and is currently used by a scenic train tour. The city is considering options to convert the rail line to trail, and could consider removal of the causeway.

A feasibility study on cleanup options for this site should be available in 2018.

The Thomson Reservoir, which is about 375 acres in size, was constructed in 1908 and consists of multiple earthen or concrete dams used to control water flow through the south portion of the Site. Elevated concentrations of dioxin/furans and mercury have been found in sediments in the Thomson Reservoir. Thomson Reservoir contain relatively low energy pools of water with well-developed ecosystems and a variety of habitat zones. Maximum concentrations of dioxin/furan contaminants exceed state sediment quality targets by more than a factor of 10 at some locations and the contaminated sediments are widely distributed within the reservoir.

A feasibility study on cleanup options for this site should be available in 2018.

The Scanlon Reservoir, which is about 40 acres in size, was constructed in 1923 and consists of Scanlon concrete dam used for hydroelectric generation. Elevated concentrations of dioxin/furans and mercury have been found in sediments in the Scanlon Reservoir. Scanlon Reservoir contain relatively low energy pools of water with well-developed ecosystems and a variety of habitat zones. Maximum concentrations of dioxin/furan contaminants exceed state sediment quality targets by more than a factor of 10 at some locations and the contaminated sediments are widely distributed within the reservoir.

A feasibility study on cleanup options for this site should be available in 2018.