About This Project
Remove and Replace Existing Bridge located at Surprise Lake, BC.
Located 20 km East of Atlin, BC, the Surprise Lake Bridge spans Pine Creek at the outflow from Surprise Lake. The existing 4-span bridge was constructed with wood stringers and deck founded on wooden piles. Due to the aging foundations the structure needed replacement.
The replacement structure was 110’ single span steel girder bridge with a composite concrete deck founded on steel pipe piles. The new bridge was also set much higher than the original structure and so the approaches required some rework.
Upon mobilizing to site work started on the new approaches. This work had to be done 30 days in advance of the construction of the new bridge to preload the soil. The new approach was about 10’ higher and 20’ wider than the original approach road.
The steel girders for the new bridge were brought onsite before the old bridge was removed so that the bridge could be used to get the girders over the creek. The girders were then placed on temporary sills.
Steel pipe piles were driven to support the new bridge. Four piles were installed at each end of the bridge and then cut off, temporary caped, and buried to allow the road to stay open. Once the piles were completed work on the approaches continued.
Following the 30 day preload the road was closed to allow the old bridge to be removed and the new one installed. A ten day road closure was allowed for the construction of the new bridge.
Once the road was closed work immediately started on the demolition of the existing structure. The wooden bridge was removed followed by a timber spillway that had been constructed in the creek channel.
The banks of the creek were pulled back from where they had been extended for the old bridge. They were sloped and armored with rip-rap.
The pre-cast concrete pile caps were welded to the piles and the steel girders swung into place using a crane at each end of the bridge. With the steel in place the diaphragms and plan bracing was installed.
The precast ballast walls were hung on the ends of the steel and then each side of the bridge were backfilled at the same time. The precast deck panels were placed on the newly erected steel using an excavator.
After the new deck was installed the joints between the individual panels and the pockets in each panel had to be formed and filled with a high strength grout. The grout cured overnight and the forms were stripped off. The next day sufficient strength had been achieved in the deck to allow the excavator back on the bridge to place the precast parapets.
After the parapets were put in place the bridge was reopened to the public right on time, exactly 10 days after the road was closed.
Following the opening of the road the downstream end of the creek banks required sloping and rip-rap as the steel girders had been in the way earlier. The approach construction was completed with the placement of the surface gravels followed by the signs and CRB’s. The Surprise Lake Bridge was complete.