Bioremediation Case Study

Project Location: Ontario, Canada

Former Trucking Distribution and Service Centre

AEL was retained to conduct a Phase 1 and 2 Environmental Site Assessment (ESA) at a former transport truck repair and maintenance property (“the Site”), situated in a residential area. Historically, the Site had been used as a truck marshalling yard, for refuelling, and as a maintenance centre. Two former truck refuelling areas and a former waste oil tank were located on the property, which resulted in petroleum hydrocarbon (PHC) impacts in and around these areas.

AEL began the project with a detailed sampling program. Prior to AEL involvement, approximately 2,500 tonnes of PHC impacted soil had been estimated at the Site. AEL undertook a Phase 2 ESA utilizing on-site testing for PHC in soil and groundwater by Ultra-Violet Fluorescence (UVF). The use of UVF enabled AEL to direct the investigation in real time over a 2-day period and delineated approximately 5,000 additional tonnes of PHC impacted soils which had not been accounted for previously. The use of the UVF by AEL’s highly trained technicians provided a deep understanding of the Site’s PHC contamination, eliminated the need for multiple site visits, and reduced lengthy wait times associated with traditional methods which require multiple rounds of laboratory results, thereby greatly reducing the timeline and cost of the Phase 2 ESA.

AEL developed a remedial plan to clean the PHC contamination and bring the Site into compliance with standards set by the Ministry of Environment, Conservation and Parks (MECP). The work was complicated by a limited time schedule, early winter working conditions and a sensitive site designation for the Site imposed by O. Reg. 153/04 due to shallow bedrock. AEL was able to “segment” the Site under by O. Reg. 153/04 and apply the sensitive criteria only to those portions of the property affected by shallow bedrock. This resulted in significant savings in assessment and remediation costs, while at the same time being protective of the natural environment.

AEL’s remedial plan consisted of the following:

  • Purging and removing the existing PHC storage tank on-site and demolition of any existing Site buildings and flooring slabs
  • Segregation and stockpiling for reuse any existing overburden that did not exceed the applicable MECP criteria
  • Excavation and construction of bioremediation treatment cells on the Site to treat soil contaminated with PHCs
  • Importing of soil fill that met the MECP criteria for backfill of excavated areas up to existing grades
  • Bioremediation of soils impacted by PHCs to meet MECP criteria 

The contaminated soil identified during AEL’s Phase 2 ESA delineation was excavated and placed into bio-piles. Soil was only excavated from areas where field screening with the UVF indicated PHC levels were higher than the acceptable MECP criteria. Lateral and vertical extents of the excavations were fine-tuned from AEL’s initial Phase 2 ESA characterization by UVF sampling along the walls and floor of each excavation. Final confirmation samples were sent to the laboratory for analysis based on UVF on-site sample results.

Following excavation, the contaminated soil was placed into three separate stockpiles. Samples of the stockpiles were taken prior to the commencement of treatment, to establish a baseline. Soil was piled on a double layer of impermeable plastic and built to a height of about 0.6 m and sprayed with a combination of PHC-degrading microbes, nutrients, PHC-degrading enzymes, and biosurfactants, all of which contribute synergistically to create a rapid and effective bioremediation of soil contaminants. All bioremediation ingredients are non-toxic and biodegradable. A protective plastic sheet was placed on top of the pile as a cover and left for one month.

After a month of treatment, a round of sampling was performed in accordance with the applicable stockpile sampling guidelines within O.Reg. 153/04. Samples were selected for laboratory analysis based on on-site testing with a photoionization detector (PID) and UVF.

Stockpiles were then turned over by an excavator to aerate them, which accelerates the rate of bioremediation. Additional liquid microbial treatment was also applied to several areas that were lagging behind the treatment timeline. The piles were then left for one additional month. Additional confirmatory samples were then taken and the soil was determined to be clean, meeting the MECP criteria.

Since the bioremediation was successful the soil was able to be re-used at the Site. By using bioremediation instead of off-ite disposal, AEL reduced the cost of the remediation by more than 50%, saving the client close to $200,000. AEL’s on-site laboratory also reduced the excavation and backfilling costs by adding confidence and precision to the soil removal work.

The remediation is now complete and the Site was purchased and utilized by a local school board as the location of a new elementary school.

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