Seismic and wind warning system goes live soon on Pattullo Bridge
Credit to Author: Jennifer Saltman| Date: Sun, 26 Jan 2020 22:28:30 +0000
The Pattullo Bridge is getting a new early warning system to protect drivers from the effects of wind storms and earthquakes.
The bridge is 82 years old, and was not built to current wind and seismic standards, leaving it — and the approximately 65,000 vehicles that cross the span each day — vulnerable.
“The seismic warning and monitoring system will help improve safety of the current bridge by closing it to vehicles and pedestrians during a seismic or high-wind event,” said TransLink spokesperson Dan Mountain. “This work is part of TransLink’s mandate to maintain the safety and functionality of the Pattullo Bridge until its replacement.”
The warning system consists of seismic activity and wind warning sensors, bridge closure devices (traffic control gates and fibre-optic cables), and lights and signs.
The sensors measure wind velocity and amplitude of seismic compressional waves, Mountain said. High-wind warnings are given for velocities between 70 and 89 kilometres per hour, and alarms at or above 90 kph. A compressional wave with an amplitude of at least 0.005 metres per second would trigger a bridge closure.
In either of these cases, the gates, which are similar to those at railway crossings, will block the entrances, and warning lights and digital signs will alert users to the closure.
The sensors are not visible, and Mountain would not reveal their locations, in an effort to prevent vandalism.
Construction was completed in December, and testing has been ongoing since, however the bridge will be closed on Jan. 31 and Feb. 1 from 9 p.m. to 5 a.m. for a full-system test. Drivers should take the Port Mann or Alex Fraser bridges instead, and N19 bus trips will be re-routed over the Queensborough bridge.
The system cost TransLink $5.6 million.
The Pattullo will be the only TransLink-owned and maintained bridge that has such a system, but the project will allow the transit authority to test the technology and evaluate how it could be used for other assets and projects.
TransLink is also responsible for the Knight Street, Golden Ears, Westham Island and Canada Line bike and pedestrian bridges.
Mayors’ Council chair Jonathan Coté said that under normal conditions, the bridge is safe, but if there is an earthquake or high-wind event, such as a hurricane, there is risk to the aging bridge structure.
“What this system does is actually makes it a lot easier to quickly close down the bridge in the event of those more serious events happening in the region, to really ensure that the public’s safety is taken into consideration,” Coté said.
Even though the bridge is set to be replaced within a few years, Coté said it is important to have the warning system in place.
“I think we have a duty to make sure that we are protecting public safety as much as we can, so even though it is only for a short period of three to four years that this will be operational, given that we know that that risk exists, I think it actually is prudent that we are protecting public safety,” he said.
The provincial government will build a new $1.377-billion, four-lane Pattullo Bridge just upstream of the existing bridge. The goal is to have it built by 2023, which is when TransLink has said the Pattullo must close for safety reasons.
Fraser Crossing Partners, a consortium of seven companies, was chosen to enter into discussions to finalize an agreement to design, build and partially finance the bridge during construction. The contract is expected to be awarded early this year.
Although the province has taken lead on the bridge replacement project, TransLink is responsible for maintaining the old bridge until it is torn down. The transit authority spends about $1 million annually on maintenance.
The Pattullo isn’t the only major bridge in Metro Vancouver equipped with seismic systems, although it doesn’t appear there are others with a system to detect strong winds.
The province has seismic sensors on the George Massey Tunnel and 14 of its bridges, including the Port Mann, Ironworkers Memorial, Pitt River and Queensborough.
According to City of Vancouver structures engineer Natalia Myles, none of the city’s bridges have early warning systems. However, the city expects to have the first phase of a seismic monitoring system done for the Granville Bridge by mid-2021, and is in the design stage for a system on the Cambie Bridge.