North Harbour

Overview of Issue:

In 1985, the International Joint Commission identified forty-three different Areas of Concern (AOCs) across the Great Lakes where the environmental quality had deteriorated to the point that the beneficial use of these aquatic areas was being impacted.  Thunder Bay was identified as one of these areas of concern for a number of different reasons including the contaminated sediment in the Thunder Bay north harbour from historic effluent discharge of a former paper mill.

The site in question is contaminated with about 400,000 cubic meters of organic sediment deposited over 90 years of mill operations. This sediment is subsequently contaminated with mercury in concentrations that range from 2 to 11 ppm at the surface of the sediment to 21 ppm at depth.  The sediment layer itself is composed of a relatively fibrous material with thicknesses ranging from 40 to 380 centimetres covering an area of approximately 26 hectares.

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In order to remediate these areas of concern the Remedial Action Plan (RAP) was implemented which sought public input on the contamination and remediation efforts through their Public Advisory Committee (PAC).  Over the years the PAC has received a variety of information on the contaminated sediment and the different options available to remediate it.  Links to these reports and presentations are presented below.

Link to North Harbour Documents

Short-Listed Remediation Options:

Option A – Dredging and Disposal at an On-Site Confined Disposal Facility

  • Construction of an on-site Confined Disposal Facility (may involve the existing lagoon footprint and/or the waterlot)
  • Installing environmental controls, such as silt curtains or temporary sheet piling around the work area
  • Removing impacted enriched organic sediment (EOS) by mechanical or hydraulic dredging (excavation under water)
  • Placing the dredged enriched organic sediment within the Confined Disposal Facility
  • Capping the Confined Disposal Facility after the enriched organic sediment has consolidated

Option B – Dredging and Disposal at Mission Bay Confined Disposal Facility

  • Enhancing or building a new engineered cell within the existing Mission Bay Confined Disposal Facility which is operated by the Thunder Bay Port Authority, located at the south end of the Thunder Bay Harbour
  • Installing environmental controls, such as silt curtains or temporary sheet piling around the work area
  • Removing impacted enriched organic sediment (EOS) by mechanical or hydraulic dredging (excavation underwater)
  • Dewatering the enriched organic sediment and treating the water as required
  • Transporting the dewatered enriched organic sediment to the Mission Bay Confined Disposal Facility and placing it within that facility
  • Capping the Confined Disposal Facility after the enriched organic sediment has been consolidated

Option C: Construction of an In-place Barrier and Infilling

  • Installing environmental controls, such as silt curtains or temporary sheet piling around the work area
  • Constructing a new berm around the limits of the enriched organic sediment and water lot boundary to the west
  • Removing enriched organic sediment (EOS) located outside of the west berm by mechanical or hydraulic dredging (excavation underwater)
  • Placing the dredged enriched organic sediment within the containment area
  • Placing a thin-layer of sand to manage marginally contaminated sediments remaining outside of the newly constructed berm
  • Infilling and capping the area within the berms over an approximate three-year period with a combination of free fill during the first year of infilling operations (such as concrete rubble or dredged materials from maintenance activities in the area) in conjunction with paid material (such as pit run material from local quarries)

Moving from Phase I to Phase II of the Thunder Bay North Harbour Sediment Remediation Project.

Link to the Thunder Bay North Harbour Sediment Management Project Update. June 23, 2022

After reviewing the Thunder Bay North Harbour Working Group’s recommendation report, TBNH Senior Management Committee has agreed to accept the recommendation of SMO A (SMO A-managing the contaminated sediment through dredging and disposal at an on-site confined disposal facility).

There are three phases to the TBNH Sediment Remediation Project:

  • Phase I – selection of the preferred Sediment Management Option (SMO) – completed
  • Phase II – complete engineering design – in progress
  • Phase III – implementation and monitoring

To this end, work is underway to prepare the tender document for the engineering design of SMO A.

With SMO A identified for the project, the Committee will re-convene to plan for the engineering design for the project. This Phase will include four main tasks:

Task 1: Completion of tender document for engineering design of SMO A

Task 2: Award contract for engineering design

Task 3: Prepare engineering design, cost estimate, permits and approvals

Task 4: Prepare specification and drawings for project implementation

The Committee is currently engaged with Task 1 above and will plan for the remaining tasks.

Here you can find more documents related to the Thunder Bay North Harbour Sediment Management Project:

Thunder Bay North Harbour Sediment Management Project Update – the full version of the memorandum that documents the work completed by the Committee for Phase I (selection of the preferred SMO)

Canada-Ontario Agreement (COA) on Great Lakes Water Quality and Ecosystem Health 2021 – sets out specific actions each government will take to protect and restore the Great Lakes

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