Extending the life of a solid waste landfill
In Ontario, Canada, the effective capacity of the City of Barrie’s municipal landfill has been increased to over 1 million cubic meters, estimated to last an additional 18 years from the original estimated closure date of 2017, the result of an award winning project for Golder.
In 2008, the City’s municipal solid waste landfill had a licensed volume of 3,900,000 cubic meters and was slated for closure in 2017. The landfill covers an area of 18.6 hectares and extends to a peak thickness of 30 meters. Originally designed as a natural attenuation facility, leachate seepage to the groundwater, and impacts to an adjacent stream, resulted in environmental risk and compliance issues for our client.
The aim of the project was to address environmental compliance issues, reduce the period and collection rate of the groundwater control systems, and recover air space, thus extending the operational life of the landfill. Golder proposed re-engineering the landfill design to allow the reclamation, or “mining”, of waste in the landfill, and to incorporate two new elements; a liner and leachate collection system, and a landfill gas collection system and flare.
Between 2009 and 2015, nearly 1,630,000 cubic meters of waste was excavated and mined, representing 44 per cent of the total licenced landfill volume. Of this, approximately 742,200 cubic meters of fines were processed through screening which can be re-used as daily cover for waste reclamation, incoming waste, as well as interim and final cover. This avoids the need to import cover material, and saves both costs and carbon emissions identified with haulage.
Groundwater control systems consisting of a drain and purge wells have been constructed to intercept the leachate, which is then discharged to the City’s wastewater treatment plant, reducing the impacts to the underlying groundwater flow. Once the existing plume in the aquifer under the landfill has been captured by the purge well system, and subsequently shut down, the flows to the wastewater treatment system will be reduced. Furthermore, the cost of operating the active purge well system will end, and the leachate collection will be limited to gravity drainage of the leachate control system.
Landfill gas collectors have been installed in the waste to remove new methane generated in the newer parts of the landfill, which are flared to reduce the effects of greenhouse gas emissions. This system is currently collecting and flaring approximately 340 m3/hr of landfill gas, and it is predicted that a maximum collection rate of up to approximately 500 m3/hour may be achieved. On this basis, and considering current approaches to funding of LFG power generation projects, installation of a 500 to 850 kW generator is considered feasible and the City will assess this as a business case.
In 2009, prior to reclamation, the remaining airspace was approximately 815,000 m3; the remaining airspace at the end of reclamation in 2015 was 1,144,550 m3. Based on the current annual waste disposal rates and population growth predictions, the total lifespan of the landfill is calculated to extend to 2035, or an 18-year gain. Had this work not been undertaken the landfill would have closed in 2017 and the City would have had to export the waste elsewhere
Golder was honored with an Award of Excellence for the City of Barrie Landfill project in the 2017 Canadian Consulting Engineering Awards, recognized as the industry’s highest honors, offered only to the most remarkable engineering feats featured in projects by Canadian firms and a great credit to the project team.