Proposed Management Limits for F2 and F3 Hydrocarbons at Remote Alberta Green Zone Sites

The overall objective of this project was to critically examine the existing management limits for petroleum hydrocarbons (PHCs) in the Alberta Tier 1 guidelines (AENV, 2010) for applicability to the Green Zone of Alberta, and develop management limits specific to the Green Zone if appropriate. The technical steering committee for this project identified the following four considerations that were considered to be appropriate for setting management limits for PHCs in the Green Zone of Alberta:

  • mobile free phase formation;
  • fire and explosion hazard;
  • hydrophobicity; and,
  • upwards migration into root zone.

The project focussed on PHC fractions F2 and F3, based on mobility considerations with F1, and the fact that F4 management limits rarely drive remediation efforts at contaminated sites.

The overall objective of this project was to critically examine the existing management limits for petroleum hydrocarbons (PHCs) in the Alberta Tier 1 guidelines (AENV, 2010) for applicability to the Green Zone of Alberta, and develop management limits specific to the Green Zone if appropriate. The technical steering committee for this project identified the following four considerations that were considered to be appropriate for setting management limits for PHCs in the Green Zone of Alberta:

  •  mobile free phase formation;
  •  fire and explosion hazard;
  •  hydrophobicity; and,
  •  upwards migration into root zone.

The project focussed on PHC fractions F2 and F3, based on mobility considerations with F1, and the fact that F4 management limits rarely drive remediation efforts at contaminated sites.

Methodology

The first three of the considerations listed above were addressed by initiating laboratory based programs to collect data to support a defensible and robust approach to quantifying these issues. The experimental programs investigated F2 and F3 PHC fractions in fine and coarse soils. The laboratory work was conducted by the Reclamation Group at Alberta Innovates Technology Futures. The fourth of the above considerations was quantified by considering the results of previous research using soil columns with a clean rooting zone over PHC contaminated subsoil.

Results

Where possible, the experimental data were used to identify threshold concentrations below which each of the four considerations noted above would not be a concern. In some cases, the data were used semi quantitatively to indicate that a particular consideration was unlikely to be limiting. This was done for F2 and F3 hydrocarbons in each of fine and coarse soils. Proposed Green Zone management limits were generated by taking the lowest of these thresholds for each hydrocarbon fraction and soil type. Proposed Green Zone management limits together with the limiting consideration for each are summarised below:

  •  F2, fine soil: 10,000 mg/kg, residual saturation.
  •  F2, coarse soil: 9,000 mg/kg, residual saturation.
  •  F3, fine soil: 14,000 mg/kg, residual saturation.
  •  F3, coarse soil: 4,000 mg/kg, hydrophobicity.