St. Louis River Interlake/Duluth Tar Site

Map of general location of SLRIDT siteThe St. Louis River/Interlake/Duluth Tar State Superfund (SLRIDT) site was a former pig iron, coking plants and a water/gas (coal gasification) plant. The SLRIDT site is on both the federal National Priority List and the State of Minnesota Permanent List of Priorities.

The SLRIDT site is located within the city of Duluth, on the north bank of the St. Louis River, approximately four river miles upstream of Lake Superior. The site includes approximately 255 acres of land and river embayments, wetlands and boat slips.

The SLRIDT site has three Operable Units (OU) including the Tar Seeps Operable Unit (TSOU), Soil Operable Unit (SOU), and the Sediment Operable Unit (SedOU). A Record of Decision document (ROD) specifying cleanup activities has been implemented for the all OUs. The ROD also specifies cleanup levels, developed by the MPCA that must be met upon completion of remedial actions and maintained into the future.

As of 2010, the majority of the remedial construction on the SedOU was completed. This site is subject to Five-Year Reviews that determine the protectiveness of the remedial actions. The most recent review was completed in 2013.

MPCA project manager: Daniel Cervin, or 218-302-6633.

2018 Five-year review

MPCA is in the process of conducting the 2018 five-year review for the St. Louis River/Interlake/Duluth Tar site. The purpose of the review is to confirm whether or not the remedies were constructed in accordance with the Record of Decision documents and if they continue to be protective of human health and the environment. The five-year review report is expected to be completed by fall of 2018.

Documents related to the five-year review are available at the West Duluth Library, 5830 Grand Ave., Duluth, MN 55807.

See the NRDA section to view NRDA related documents.

Historical photo of SLRIDT siteIn 1916, Duluth Tar Company became Barrett Tar Company, which closed in about 1924.

A new tar refining operation was built in 1924 in Area E, adjacent to the Duluth Tar Company/Barrett Tar Company facility. The new facility, owned by Dominion Tar Company and American Tar Company, operated until 1948. These facilities purchased coal tar from Zenith (later Interlake), operated batch coal tar stills and manufactured tar products. The tar and chemical companies closed down by 1948, and the most recent iron plant has not operated since about 1960. 

In 1929, Zenith Furnace Company’s coking operations were relocated to Area B (the head of the current Hallett Slip 6) and the company became the Interlake Iron Company. Its water gas plant remained in Area D. Crude tar produced from coking operations at the Interlake Iron facility was sold to the tar refineries located in Area E. Other industrial byproducts were used in conjunction with re-deposited native sediment as fill to create new land, including the 59th Avenue Peninsula and the 54th Avenue Peninsula. The primary fill material is slag from on-Site pig iron operations.

Interlake Iron’s operations ceased in 1961, and the property was idle until 1966, when Hallett Dock Company (Hallett) purchased the former Interlake Iron portion of the SLRIDT site. Hallett has used the property primarily for bulk storage and handling of coal, coke, bentonite, and other industrial materials. Hallett has sold and/or leases northern portions of the SLRIDT site to other companies.

The sources of contamination in the sediments at the SLRIDT site were primarily wastewater discharges that began in the early 1900s from the water gas, coking and tar facilities formerly located on the SLRIDT site. The last operating industrial discharges from these facilities were terminated no later than 1961 when Interlake Iron shut down the last operating facility. Waste discharge areas include the Area F crescent shaped pond and Area A and E discharge pipes that drained into Stryker Bay. Area C pond and the 48 inch outfall pipe discharged into Keene Creek Bay and the southern tip of the 54th Avenue Peninsula.

The SLRIDT site is within the West Duluth neighborhood of the City of Duluth, on the north bank of the St. Louis River, approximately four river miles upstream from Lake Superior.

The SLRIDT site includes approximately 255 acres of land and river embayments, wetlands, and shipping slips. The land includes the 59th Avenue (Hallett) Peninsula, the 54th Avenue Peninsula, and is bounded on the north by the Burlington Northern right-of-way. Site features are identified on the below site map.

The aquatic portion of the SLRIDT site includes Stryker Bay (approximately 41 acres and defines the western boundary), Slip 6 (about 15 acres), and Keene Creek Bay/Slip7 (about 38 acres and defines the eastern boundary), and the St. Louis River to the south. A small portion (approximately 0.3 acres at the mouth of Slip 6 and 1.1 acres in the Minnesota Slip – aka the Federal navigation Channel) is within the waters of the State of Wisconsin.

Residents are located west of the site on the 63rd Avenue Peninsula, and to the north of the railroad tracks. According to the 2000 census, approximately 960 people live within one half mile of the site.

In 1979, MPCA staff detected PAHs in Stryker Bay sediments. PAHs are a group of carcinogenic and non-carcinogenic compounds formed during the combustion of coal, oil, gas, wood and other substances. At the SLRIDT site, PAHs are a by-product of the production of water (town) gas, high-temperature coking of coal and the distillation of crude tar. 

In 1980, MPCA staff’s analysis of samples from Stryker Bay’s surface water showed the presence of PAH compounds. In addition, in 1981 a local resident reported oil rising to the surface of Stryker Bay, which stemmed from the slow release of coal tar waste mixed in with sediments. 

In 1983, the U.S. Environmental Protection Agency (EPA) evaluated the SLRIDT site and the St. Louis River/U.S. Steel site (located on the St. Louis River approximately 4 river miles upriver from the SLRIDT site) and added them as a single site to the National Priorities List (NPL) (the federal Superfund list). The federally listed site is referred to as the St. Louis River/Interlake/U.S. Steel site. Although the two sites are listed as one on the NPL, they are listed separately on the Minnesota Permanent List of Priorities (the State superfund list) and are being investigated and cleaned up separately. 

To obtain input on community concerns about the cleanup of the SLRIDT site, the MPCA staff established a community work group to discuss the issues and complications involved with the investigation and cleanup of the site. The work group consisting of representatives from neighboring residents, local community associations, current landowners, environmental groups, Responsible Parties, city officials, MPCA officials and other interested parties group first met in March 1995.

As part of the initial SLRIDT site investigations, the MPCA staff identified four Responsible Parties, three of which have taken and/or agreed to take remedial actions for various portions of the SLRIDT site. The three Responsible Parties that have agreed to take remedial actions for the Sediments Operable Unit are:  the XIK Corporation (formerly the Interlake Corporation or “Interlake”), Honeywell Inc. (formerly AlliedSignal Inc. or “Allied”), and Domtar Inc. (Domtar) (collectively called the Companies). The fourth Responsible Party, Beazer East, Inc. (Beazer) has refused to participate. 

Further investigations revealed contamination that was categorized by the MPCA into one or more of the three operable units (OU)– Tar Seeps, Soil, and Sediments. Groundwater at the SLRIDT site is also contaminated and is being addressed under the soil and sediment operable units.

The MPCA issued Requests for Response Actions (RFRAs) in March 1991 and May 1993 to the Responsible Parties to clean up the Tar Seeps and Soil Operable Units. The Companies completed cleanup of the Tar Seeps Operable Unit in 1994, and the Soil Operable Unit in 1997. Both operable units were cleaned up to industrial land use standards. Groundwater monitoring is being addressed as part of the five year review of the Soil Operable Unit.

The Sediment Operable Unit included approximately 450,000 cubic yards of sediment that exceeded MPCA standards for contaminated sediment. The MPCA issued two RFRAs for the Sediment Operable Unit: one in March 1994 to Interlake (now XIK Corporation), and a second one in March 1996 to Beazer, Allied (now Honeywell) and Domtar.

In November 1999 the MPCA presented a Proposed Plan to the public for cleanup of the Sediment Operable Unit which was opposed by the Companies. In February 2000, the Companies and MPCA entered an agreement to reopen the Remedial Investigation/Feasibility Study (RI/FS) process, to gather information to fill data gaps, and to evaluate four cleanup alternatives: No Action; Wetland Cap; Dredging and On-Site Disposal; Dredging and Off-Site Disposal. 

Additional data collected to fill the data gaps was submitted to the MPCA in the November 27, 2002 Data Gap Report. The MPCA facilitated a two-day meeting in February 2003 to discuss the remedy implications of this new information. The meeting included representatives of the Companies and their consultants, MPCA staff, the Peer Review Team, State, federal and tribal natural resource managers, property owners, area residents, the City of Duluth, and other stakeholders. 

Using the information developed at the February 2003 meeting the Companies, the MPCA, and the DNR identified a hybrid cleanup alternative to be evaluated in the Feasibility Study. However, additional studies revealed that the capacity for storing dredged material in the original CAD in Slip 7 was overestimated, and the volume of material to be dredged was underestimated. Therefore, the Dredge/Cap Hybrid Alternative was revised to move the containment of dredged materials from Slip 7 to Slip 6. The Agreement was also amended to reflect this revision in the hybrid alternative (Amendment No. 2) and the Feasibility Study Revised Addendum 1 was developed by the Companies to evaluate the revised hybrid alternative.

In 2004 a Record of Decision (ROD) documented the dredge/capping hybrid as the remedial action, and in 2005 a Remedial Design/Response Action Plan (RD/RAP) was approved. Remedial action in the form of a pilot capping project was conducted in 2004. Further Remedial action took place from 2006 to 2011 and is documented in the Project Completion Report, 2013. In August 2013, a Long Term Monitoring and Maintenance (LTM&M) plan was approved for the Sediment OU.  The monitoring component will determine short term performance over a five year period using a tiered approach. Long term monitoring will continue as long as the contamination remains on site.

In 2013, the third Five Year Review was completed by the MPCA. It indicated that the Soils OU was not fully protective of human health, and several issues needed to be addressed. They included tar layers, and a small tar seep area, and remnant tar found in onsite soils. The Sediment OU was found to be protective in the short term; however institutional controls such as dredging restrictions are needed to ensure long term protectiveness.

Sediment (SedOU)

Operable unit

Current status remarks


Tar Seeps (TSOU)

Complete March 1994

Tar from Seeps was excavated and transported off-site for recycling as a fuel source. Excavation was achieved by placing the tar/soil mixture in 14 roll off boxes for subsequent transport in September 1992. Transport occurred from September-October 1993 and approximately 192 tons of fuel-grade tar was removed from Areas B, D, and the 48-inch outfall pipe. It was taken to the Missouri Fuel Recycler/Continental Cement Company of Hannibal, Missouri. 

Soil (SOU)

Complete October 1997

From May 28, 1996 through October 21, 1997, contaminated soil was cleaned up using excavation and low temperature thermal treatment of soil and off-site disposal, structure decontamination, and bioventing in Maurice’s Parking Lot. The soils were cleaned up to accommodate an industrial setting. A total of 30,441 cubic yards of soil and debris were remediated.


The 2013 Five Year Review found that the SOU was not protective of human health and the environment until both long term and short term issues are addressed. Short term issues include a Tar layer on the west side of Stryker Bay, a tar seep near Area E, and residual tar near areas B and C. Long term issues noted in the 2013 Five Year Review include completing an updated Risk Assessment focused on indoor air quality and updating cleanup goals.

Sediment (SedOU)

Complete 2011

Approximately 600,000 cubic yards of contaminated sediment were present in the water bodies within the boundaries of the SLRIDT Site. The Record of Decision (ROD) was completed in August 2004 and the Revised Dredge/Cap Hybrid Alternative was chosen as the preferred cleanup alternative. A Remedial Design and Response Action Plan (RD/RAP) was accepted in 2005 and construction conducted from 2006-2011. A Long Term Monitoring and Maintenance plan was approved in 2013. Monitoring and maintenance activities are ongoing.



Institutional controls are needed to ensure the remedy remains protective in the long-term.

Site events:   



PDF icon (Long-Term Monitoring Report Year Four - SLRIDT Project (c-s3-17f)


PDF icon Long-Term Monitoring Report Year Three - SLRIDT Project (c-s3-17e)


PDF icon Long-Term Monitoring Report Year Two - SLRIDT Project (c-s3-17d)


PDF icon Long-Term Monitoring Report Year One - SLRIDT Project (c-s3-17c)


Long Term Monitoring and Maintenance Plan


Third Five Year Review


Construction completion


Install Cover on Slip 6 CAD


Remove Surcharge from Stryker Bay Cap


Second Five Year Review


Armor Remaining Areas


Dredge Additional Channel Material


Dredge WI Portion of Channel


Dredge MN Portion of Channel


Dredge South of Slip 6


Stryker Bay Cover


Slip 7 Wetlands Excavation/Capping


Dredge Stryker Bay


Construction of Water Filtration System


CAD end dike construction

July 2006

Sheet Pile installation

June 2006

Cap and Surcharge in Stryker Bay

Summer 2006

Dike Construction Begins

April 2006

Remedial Design/Remedial Action Plan on the Sediment OU


Pilot Test Capping in Slip 7


Record of Decision (Sediment Operable Unit)


Public Comment Period (For sediment operable unit proposed plan)


Remedial Investigation (Data Gap Report Approval-reopened RI reports)


Feasibility Study (Approval of Reopened and Revised FS)


First Five Year Review


MDH Health Assessment/Consultation


Remedial Investigation (Reopened Phase II Work Plan)


Remedial Investigation (Reopened Phase IIIB Work Plan)


Remedial Investigation (Reopened Phase IIIA Work Plan)


Ecological Risk Review (To determine sediment cleanup goals)


Field Sampling Event by MPCA (Bay West)


Agreement between MPCA and the Companies for Additional Sediment Investigation


MPCA Rescinds Record of Decision for Sed OU


Request for Response Action issued to the Companies (Responsible Parties) for the SedOU


Remedial Action for Soil OU


Record of Decision selecting the remedy for the Soil OU


Tar Seeps Remedial Action Completed


Request For Remedial Action (RFRA) issued for the Tar Seep OU


Request For Remedial Action (RFRA) issued for the Soil OU


Record of Decision selecting remedy for the Tar Seep OU


PLP Listing Date


NPL Listing Date


Site Discovery when PAH contaminated detected by MPCA


Updated annually
Last revised: April 2017


Soil/Tar Seeps Operable Unit

Sediment Operable Unit

Location of site documents and records:

Duluth MPCA
525 Lake Ave. S
Suite 400
Duluth, MN  55802
Phone: 218-723-4660
Fax: 218-723-4727

Archived list of meetings:

  • June 14, 2011 – Construction Wrap Up Meeting
  • November 16, 2007-Community Workgroup Meeting
  • October 3, 2007-Community Workgroup Meeting
  • June 13, 2007-Community Workgroup Meeting 
  • March 14, 2007-Community Workgroup Meeting
  • May 10, 2006 – Community Workgroup Meeting
  • April 12, 2006 – Community Workgroup Meeting
  • February 23, 2006 – Community Workgroup Meeting
  • September 29, 2004 - Community Workgroup Meeting
  • September 1, 2004 – Community Workgroup Meeting
  • May 10, 2004 - Proposed Plan Public Meeting
    • MPCA Proposed Plan for the Sediment Operable Unit (Presentation)
  • November 25, 2003 - MPCA Citizens’ Board Meeting to Approve Amendment No. 1 to the Agreement.
  • September 11, 2003 - Community Workgroup Meeting to update community on progress
  • August 12, 2003 – Workshop Meeting to Discuss Proposed Remedial Alternative Option for the Cleanup of Contaminated Sediments
  • May 15, 2003 - Five-Year Review Meeting.