S3S provided a mobile slurry treatment system to process jet-grout backflow spoils on a highly congested site in Midtown Toronto.
During jet grouting, a significant return flow of soil, grout and water, known as backflow, comes back to the surface. Backflow is traditionally held in large pits or hauled away in vacuum trucks to contaminated waste facilities.
The volume of waste varies with the diameter and depth of the columns drilled. This project sat in a very congested area of Toronto with minimal room for pits. Hauling backflow by vacuum truck is expensive, hard to run in heavy traffic, and raises the safety risk to site personnel and the public.
S3S ran a mobile slurry treatment system of tanks, centrifuges, and flocculation additives to treat the backflow, producing a dry, stackable solid at a reduced volume. The dry waste eliminated the need for vacuum trucks and cut the total number of truckloads. Clear water was recovered, reused in the operation, and discharged to the sanitary sewer with no additional processing.
Every figure here comes from the Eglinton Crosstown East Tunnels project.
Each column processed through the mobile treatment system produced 40 cubic metres of free water from the backflow.
Dry, stackable waste and recovered water cut overall waste handling costs by 20%.
Backflow moved from the contractor through the slurry treatment system to two outputs: dry solids and clear water.
S3S receives the backflow from the contractor and sends it to the slurry treatment system.
All heavy solids, such as sand and gravel, are removed first.
The remaining slurry is processed through the slurry treatment system as flocculants are added.
The solids leave as a dry, stackable material ready for landfill, and the clear water is reused in the operation or discharged to the nearby sanitary sewer, meeting provincial discharge criteria.
Producing a dry, stackable waste on site made haul-off more efficient, reduced risk, lowered handling costs, and increased clear water recovery. Processing the jet-grout backflow cut disposal costs by 20%.