Bridge Pier Rehabilitation, MB

Bridge Pier Rehabilitation,
Underwater Concrete Repair

St. Andrews Lock and Dam, Red River, Lockport, Manitoba

Public Works Government Services of Canada

Eight Weeks

The structure which spans the Red River north of Winnipeg, was constructed in 1910 for the purpose of regulating the water elevation upstream for navigation purposes. It is owned and operated by the federal government and is considered a historical site due to its unique design and function.

Diver carrying out concrete repairs to the rollway.

Elements of the structure include a two-lane bridge supported by five in-water piers divided by six fixed dam bays with water regulating curtains. Other supporting elements include a fish ladder, lock and abutment wing walls.

Dominion Divers was the successful bidder for the RFP to complete underwater concrete repairs including localized patching and grouting of badly spalled areas, and crack injection, typically located within the freeze-thaw zone situated along two horizontal cold joints. The underwater work was carried out under low to zero visibility conditions.

The set-up included the use of two barge platforms surrounding the pier, swing stages, a 40,000 psi water blaster, hydraulic and pneumatic tools and a concrete plant and pump.

A marine traffic plan was implemented as the area is known for high volumes of recreational boating, fishing, and tourist usage. Controls were implemented to ensure the safety of the public and the dive crew.

Loading concrete bucket with grout and 10mm pea gravel to continuously feed the pump.

The perimeter of areas to be repaired were saw-cut to a minimum depth of 25mm. Unsound concrete was removed with hydraulic and pneumatic chippers, then the entire surface was water blasted at 40,000 psi to clean and roughen the surfaces. Rebar dowels were drilled and installed with adhesive and reinforcing bars were installed and tied. Dominion Divers built custom formwork panels for the project which could be installed in various configurations and with minimal anchoring requirements. An engineered concrete with an anti-washout admixture and plasticizer was batched on the barge and pumped through ports on the formwork.

The surface areas for crack injection were prepped with a 40,000 psi water lance as deep as could be reached, then grout ports were installed, and the crack opening patched. The cracks were flushed with high pressure water prior to injection with an epoxy grout.

The quality assurance program included concrete batch samples and break tests, core samples of spall and crack repairs and video post form removal, using a clear water box fixture for the camera.