As Metro Vancouver awaits a new Pattullo Bridge, crews took on the task of extending the aging bridge's life by doing a $10-million rehabilitation of the deck.
Bob Moore, manager of bridge operations for Translink, explained the steps crews took to ensure the project went smoothly and safely during this year's Association of Consulting Engineering Companies – B.C. Transportation Conference.
The repairs addressed concrete delamination on sections of the 79-year-old bridge. Crews had to mill off the asphalt surfacing from the deck, remove all deck concrete down to the top layer of rebar, repair the concrete delamination, clean or replace rebar and repave the deck area with a concrete overlay.
Moore said crews took off between 100 and 120 millimetres of concrete and asphalt, and instead of recasting old deck, 50 millimetres of new deck was cast into new overlay. In total, crews repaired 1,180 square metres of deck with 67 full-depth repairs.
"The rehab was to increase the service life by 10 years," Moore said.
When crews began the work they found dozens of small holes as well as 15 to 20 large ones.
"It be became clear that it was important and we went ahead with this project," he said.
Because the bridge is a major vein between Surrey and New Westminster, a major concern was dealing with traffic. New Westminster police were able to assist by doing enhanced enforcement at the beginning of each phase, checking for speed, distracted driving and more.
"We felt this was necessary because of the confined working space," Moore said. "It certainly had an impact on peoples' speed and behaviour."
Environmental concerns were also an issue. The project was nearly held up by two raptors who used the bridge to roost and feed from. However, after a monitoring program started it was discovered they weren't nesting there anymore. The repairs were also well received by the public, thanks to good planning and community education, Moore said.
Drivers were warned well in advance of traffic changes and nearby homes received schedules of planned noise. Moore said safety was also a top priority. At the start of each stage, diversions were in place on the weekend and a 48-hour peer review of their placement was completed and changes were made if needed.
The team used large Ontario barriers, which despite some impacts, showed no visible movement. Moore added that their perceived mass appeared to influence driver behaviour. There was only one serious wreck reported when a car attempted to drive the wrong way down the one-lane bridge.
"The barrier size was a traffic calming situation," he said, noting it also inspired confidence in the workers. They also were able to attach equipment to the barriers.
The project began in May 2016 and finished a month early in August. Despite some rainy West Coast weather in June, crews were able to get more done in a shorter period of time by scheduling additional weekend and overnight closures and reducing the number of concrete pours.
Due to cost savings, the crews were even able to do additional work, including soffit repairs, soffit scaling and removing abandoned watermains.
Moore attributed the success to preparation, early involvement from the contractor, a good team ethos, a combined site office and an appropriate response when things didn't go to plan.
Moore added that a disciplined application of special provisions produced a high quality overlay.
"They stuck hard and fast to the specs and that is why we ended up with quality," Moore said.
Metro Vancouver officials intend to eventually replace the aging bridge with a four-lane span with the option of widening to six lanes. The new bridge would also include modern lane widths, a centre barrier and paths for pedestrian and bicycle traffic.