Brief

In Calgary, Alberta, a former retail gas outlet belonging to a large international retailer had released petroleum hydrocarbons (PHCs) into the subsurface resulting in a plume that had migrated underneath a residential neighbourhood. Remediation using a Dual Phase Vacuum Extraction (DPVE) system failed to reduce the dissolved phase concentrations to acceptable levels, therefore a new solution was required to stop the further flow of contamination underneath the residential neighbourhood.

Process

The retailer hired an environmental consulting firm to assess the extent and flow of contamination of the site and in the adjacent neighbourhood. The consulting firm concluded that a Permeable Reactive Barrier (PRB) was the most appropriate response to mitigate the transport of PHCs underneath the neighbourhood.

IRSL worked alongside Regenesis to design an effective PRB for the site. Regenesis is the manufacturer of PlumeStop, a proprietary form of colloidal activated carbon (CAC), and ORC, which were utilized to form a PRB to mitigate the migration of the PHCs. The combination of these reagents allowed for a flexible treatment approach to the PHCs, using adsorption and aerobic biodegradation to treat the PHCs.

Challenges

The large scale, the largest implementation of PlumeStop in Canada thus far, required the development of an efficient procedure and system for injecting large volumes daily.

The depth and vertical heterogeneity of the geology and plume required detailed characterization by the consultant in order for a cost and technically effective design to be developed and implemented.

The public location of the injection, as well as harsh winter weather conditions for the duration of the project, necessitated detailed logistical planning regarding for the storage, movement, mixing and injection of the reagents.

Results

The reagents were injected effectively throughout the PRB target zone on budget and under the time estimated. Preliminary results indicated that the PRB is performing as designed.

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