County seeks approvals for interim closure of Riverstown landfill phase one

Wellington County will be seeking approvals for an interim closure of the phase one portion of Riverstown landfill as part of its strategy for the dump.

The phase one mound is expected to reach capacity in late 2021 or early 2022, states a report from solid waste services manager Das Soligo in the solid waste committee update on June 28.

He said phase one has an approved capacity of 929,000 cubic metres and has an allowable elevation of 450 metres above sea level (masl).

Waste settles under its own weight, so environmental engineering consultant SNS-Lavalin said the county could apply an interim cover now and let the mound settle and open phase two for use.

“The county could seek permission from the MOECC, to bury waste to its defined maximum elevation, and then apply an interim cover,” stated Soligo in his report.

“While phase two operations are underway, the phase one waste mound would gradually settle below 450 masl.”

For every metre of settlement that occurs, an average of 37,000 cubic metres of volume would be regained, said Soligo.

“While Wellington County has never utilized this approach, it is somewhat common at other landfill sites in Ontario and elsewhere,” stated Soligo.

“An interim closure has the benefit of delaying final closure capital costs, as well as regaining capacity at a later date which would otherwise not be utilized.”

County approved the committee recommendation to allow staff to seek provincial approvals for an interim closure of phase one.

Opening up phase two means the county would have to treat leachate before development.

Leachate is water that has percolated through a solid and leached out some of the material. In phase one, it is being managed through a natural attenuation process, said Soligo. He added there is a contingency plan in place, that required collection and treatment only if groundwater quality parameters exceed “trigger level conditions.”

However, the new phase two development is required to be an engineered site with leachate collection and treatment. The analysis outlined several treatment options, including on-site treatment and treatment through a municipal wastewater treatment plant. The later is the most cost-effective and a long-term solution, stated Soligo.

County council approved the committee’s recommendation for staff to seek out a leachate treatment solution with a local municipal wastewater treatment plant, and if it is not available, to then solicit requests for proposals for an on-site process.