Remedial Action Plan - Lot L & Remedial Action / Risk Management Plan - Lot 21E

Completion of the design of a detailed environmental remedial action plan for Lot L, former trucking yard and asphalt plant (FCSI 05317002) located in Opaskwayak Cree Nation, Manitoba. The overall remedial objective for the site is to alleviate the environmental liability by addressing petroleum hydrocarbon (PHC) contamination in soil and inorganic constituents in groundwater (i.e., manganese, iron, chloride, sodium, arsenic and aluminum).
The outcomes of a human health and ecological risk screening completed for the site have identified areas on-site, including the area around MW19-41 and BH21-08 and the area around MW21-02, that exceed the petroleum hydrocarbon (PHCs) fraction F2 human health-based soil to vapour inhalation guidelines, and could pose a potential future human health risk if buildings are constructed on-site. The two (2) areas are summarized as follows:
> Remediation Zone 1 – A 335 m
2 area of PHC F2 impacted soil at a depth of 0.5 to 2.5 meter below ground surface (mbgs); and
> Remediation Zone 2 – A 210 m2 area of PHC F2 impacted soil at a depth of 0 to 1.5 mbgs.

Excavation and off-site disposal at Tervita, a licensed PHC treatment facility, near The Pas, Manitoba was determined to be the most viable option and recommended for implementation. Confirmatory soil sampling will be completed along the sidewalls and base of the excavations to confirm concentrations remaining are below applicable guidelines. The excavations will be backfilled with clean imported borrow and granular material. The liability associated with the impacted soils will be transferred to the soil treatment facility once the material is accepted. It is noted that there are several areas where manganese exceeds the Maximum Acceptable Concentrations (MAC) drinking water guideline on-site. The manganese in groundwater is a direct result of low oxygen reducing conditions caused by low-level residual hydrocarbon degradation. Removing the two (2) Remediation Zones of elevated PHCs on-site, as noted above, will aid in reducing manganese concentrations in groundwater on-site over time. Although because of the ubiquitous lower-level hydrocarbon impacts across the site and the tight, low-oxygen groundwater, elevated manganese will likely persist for many years. As a result, potable water derived from near surface (i.e. shallow or dug wells) will require pre-treatment filtration to remove excess manganese or other metals that do not meet aesthetic objectives. Alternatively, the potable water supply source for future facilities could either be deep drilled wells, or connecting these to the municipal water supply.
Lot 21 E – Carrot River (Former Borrow Pit): Completion of the design of a detailed environmental risk management plan (RMP) and remedial action plan (RAP) for Lot 21E Borrow Pit on Kiche Maskanow (FCSI 05317012) located in Opaskwayak Cree Nation, Manitoba.The overall remedial/risk management objective for the site is to alleviate the environmental liability by addressing sources of impacts and physical hazards, including buried derelict vehicles and metal debris from former waste disposal practices on-site. The purpose of the work is to prepare the site for possible future residential development or as an access roadway. The RAP/RMP consists of off-site disposal of physical hazards (metal debris and derelict vehicles) and backfilling debris excavation zones for the purpose of general public safety, and to prepare the site for potential residential development. It is estimated that 60 tonnes of metal debris and 50 tonnes of impacted soil associated with buried vehicles requires removal from the site and off-site disposal. The risk management plan should be implemented within a period of approximately three (3) weeks after contractor mobilization.


Lot L: The remedial action plan for alleviating residual risk at the site includes the following:

  • Clear shrubs and trees for access to the area where the buried septic tank is located;
  • Decommissioning groundwater monitoring wells;
  • Excavation of impacted soil in Remediation Zone 1 and Zone 2 and off-site disposal;
  • Water management during excavation activities and off-site disposal at treatment facility;
  • Reinstate excavation areas with common fill, and granular material;
  • Decommissioning and removal of partially buried septic tank; and
  • Site restoration to match surrounding conditions.

Lot 21E (Former Borrow Pit – Carrot River): The remedial action/risk management plan for alleviating residual risk at the site includes the following:

  • Clear trees for access to the areas designated for metal debris removal;
  • Excavation and off-site disposal of physical hazards (i.e., metal debris and derelict vehicles);
  • Reinstate areas of buried debris removal with common fill;
  • Removal and disposal of residual soil impacts if encountered under buried debris; and
  • Decommissioning groundwater monitoring wells.

Based on conversations with OCN, it is noted that infilling the standing water area and pond will be undertaken in a separate contract involving preparation work for the construction of new access roads or a subdivision development.


Latest update

November 22, 2021 – Indigenous Services Canada issued its notice of determination and determined that the project is not likely to cause significant adverse environmental effects.


Key documents


Indigenous Services Canada
Shelly Johnson, Environmental Specialist
365 Hargrave Street
Winnipeg, Manitoba R3B 3A3
Telephone: 204-984-0709

  • Location

    • Opaskwayak Cree Nation (Manitoba)
    • Opaskwayak Cree Nation (Manitoba)
  • Nature of Activity

    • Remediation and conservation
  • Assessment Status

  • Start Date

  • Proponent

    Opaskwayak Cree Nation
  • Authorities

    • Indigenous Services Canada
  • Assessment Type

    Project on federal lands
  • Reference Number


This map is for illustrative purposes. The markers represent the approximate locations based on available data. More than one marker may be identified for a given assessment.


Nearby assessments

...within 200 kilometres
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