CASE STUDY: Petroleum Hydrocarbon Remediation in the Northwest Territories

Using Chemical Oxidation with Percarbonate to remediate Petroleum Hydrocarbons in Permafrost Conditions.

Background

In Canada’s remote Northwest Territories, in the town of Fort Simpson, a historical fuel oil spill of unknown origin on the site of a demolished building required remediation to mitigate risk to the population, surrounding wildlife, and aquatic life in the nearby Mackenzie River. The remote location (an hour’s flight from the closest city of Yellowknife), the very short summer season, and permafrost conditions, made remediation challenging.

Location: Fort Simpson, Northwest Territories, Canada

Client: Provincial Government

Duration: 1 week

Geology: Silty Sand

Soil Treated: Approximately 120 m3

 

Approach

An environmental consultant hired by the provincial government characterized the site and determined that the soil at the site was contaminated with petroleum hydrocarbons with concentrations between 17,000 mg/kg – 32,000 mg/kg. The consultant sub-contracted IRSL to complete the project based on their reputation, preparedness, and experience in remote regions.

Chemical Oxidation with Percarbonate

To remediate the petroleum hydrocarbon within the silty sand, IRSL used soil mixing with percarbonate to chemically oxidize the petroleum hydrocarbons within the soil.

 

Treatment

To break down the petroleum hydrocarbons in the silty sand, a general contractor excavated 120 m3 of contaminated soil and mixed it with sodium percarbonate under the supervision of IRSL. The cold climate necessitated a reagent that would work effectively at low temperatures. Percarbonate was chosen due to its stability, as well as its non-reactivity with utilities and below-ground infrastructure.

The percarbonate provided an easily transportable form of oxidant that was effective for the destruction of the contaminants. Through careful and vigorous mixing, direct contact with the soil caused this reagent to chemically oxidize the hydrocarbons, resulting in the production of harmless by-products.

 

Chemical Oxidation

Chemical oxidation involves the transfer of electrons from one compound to another. Oxidizing compounds (i.e. oxidants) accept electrons from reduced species such as organic carbon-based compounds. When designed correctly, this reaction results in the transformation of contaminants into harmless compounds.

Percarbonate

Environmentally-friendly, relatively low cost, non-toxic and easily transported, percarbonate provides a safe and easy-to-use solid-form option for carrying hydrogen peroxide to conta

Challenges

  • The remote region required choosing a stable oxidant that could be shipped safely over long distances and within varying temperatures.
  • Limited access to equipment and technical tools required a simple approach.
  • The northern climate required completing the project in the very short summer season when road access was open and temperatures and weather permitted excavation.
  • The permafrost conditions made mixing the soil difficult.

Results

  • The remedial program was executed in one week.
  • The petroleum hydrocarbons were treated to below the applicable regulatory standards.

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