BOS Environmental Solutions, now Stage 3 Separation, provided slurry management services for the Gordie Howe International Bridge Project, one of the longest bridges in North America.
Polymer drilling fluid used in the cased drilled-shaft process was recycled through the patented BOS tank process for reuse during construction of an international six-lane bridge spanning more than a mile and a half.
Conventional settling tanks take days for solids to drop out, and over time the solids go colloidal and stop settling at all. The fluid gets heavier until it has to be disposed of. Settling also needs a much bigger footprint and segregated storage, which roughly doubles the polymer needed on the job.
S3S built a BOS Tank system with two large-bowl centrifuges and staffed it with one technician who ran the entire fluid system: removing drilled clays, sands and silts from the polymer, and mixing fresh polymer to spec. Polymer returning from a shaft was pumped to a holding tank, processed daily, and the clean recovered fluid pumped straight back to the shaft for reuse.
Every figure here comes from the Gordie Howe International Bridge project.
Shafts 6 to 10 ft (2 to 3 m) in diameter and up to 120 ft (36 m) deep.
Each shaft used roughly 60,000 gallons (230 m3) of polymer fluid, recovered and returned rather than replaced.
Continued reuse of recycled polymer kept approximately 160,000 gallons (600 m3) out of disposal every two weeks.
Polymer fluid moved through a controlled reuse loop, from the shaft to the BOS system and back.
About ten 18,000-gallon tanks of polymer fluid were built to specification to begin the project.
As drilling began, polymer from the shafts was pumped to a holding tank, where solids processing began.
S3S processed the polymer slurry daily, removing the solids so the client could reuse the same fluid for ongoing and concurrent shafts.
Solids-laden polymer returning from each shaft ran through the BOS system, and the recovered polymer was pumped back to the shaft for immediate reuse.
Technicians tested onsite to keep all reused polymer drilling fluid at the target rheology.
Processed fluid left a solid, stackable waste stream that passed the paint filter test and went directly to a clean landfill.
No vacuum trucks were needed until the end of the project, to clean the tanks before leaving site.
The BOS tank system and onsite fluids management cut operating costs by reducing drilling fluid consumption and the disposal fees that come with it. Recycling and reusing the polymer saved time and cost, met the fluid management and rheology objectives, and took numerous trucks off public roads.