CASE STUDY: PCE Remediation in North York, OntarioUsing an innovative, green approach to remediate land for residential development.
To expedite a residential development project in the Greater Toronto Area, a vacant lot on former farmland required remediation, in a short time-frame, to meet regulatory standards and enable the developer to attain permits. The unexpected contamination by the chlorinated solvent PCE (Tetrachloroethene) was assumed to have resulted from one or more unidentified historical spills.
Location: Greater Toronto Area
Client: Provincial Environmental Consulting Firm, on behalf of the Land Developer.
Duration: 7 months
Project Value: $43,000 CDN
Geology: Silty sand
Plume Size: Approx. 15 m x 20 m
Upon discovery of the contamination, the land developer contracted a provincial environmental consulting firm to characterize the site and complete initial sampling. The consultant managed the tendering of the project for bid to three companies, who each submitted recommendations for remediation. Broad methods were evaluated, including dig and dump, chemical oxidation, chemical reduction, air sparging and soil vapour extraction. IRSL earned the contract with the land developer based on their innovative approach, which cost significantly less than the other methods proposed.
Enhanced Anaerobic Bioremediation
To mitigate the PCE and its daughter products, IRSL developed and executed an in-situ anaerobic bioremediation plan. Requiring no infrastructure, this progressive approach ensured a very small ecological footprint.
IRSL used anaerobic bioremediation to mitigate the PCE (Tetrachloroethene) plume. Using Direct Push Technology (DPT) with specialized injection tools, they injected Emulsified Vegetable Oil (EVO) on a grid of injection points, spaced every 3 – 4 metres, at different vertical intervals.
In this anaerobic bioremediation technique, vegetable oil donated electrons to enhance the reductive dechlorination of the PCE and its daughter products by native bacteria into such harmless byproducts as ethene, chloride, and water.
Vegetable oil is a cost-effective slow-release electron donor with greater hydrogen release efficiency than other electron donors. Emulsification ensures small, uniform droplet sizes that distribute evenly throughout the plume.
- Completed in 3 days.
- Since this progressive approach is new to Canada, it required effort to convince the client to trust that the approach would work effectively within the scope presented.
- Completed in January, the cold temperatures made the vegetable oil very viscous, necessitating specialized equipment to enable injection.
- After the initial injection, the consultant completed independent testing, which confirmed that all contaminants had been reduced to below the Ministry of Environment’s Table 2 Standards for residential sites for PCE and its daughter products.
- Post-injection samplings have confirmed that the site has remained within Ministry Standards.
- The project was completed on time and on budget, enabling the developer to attain their permits and proceed as planned.