Editor:
Re: Who benefits from a bridge?, Feb. 5
All of us would like to think that our government representatives are making the best choices for the benefit of the many. Your article contained a few references about the apparent "higher risks" and financial consequences relating to "current seismic standards" of the George Massey Tunnel, or of any replacement tunnel, compared to a "safer, more seismically sound" bridge.
If it is true that our 57-year-old tunnel has reached the end of its life cycle of earthquake resistant design, it would end any debate about future use. Perhaps the seismic upgrading spent on the tunnel did not buy enough life extension. I read through an old Deas Island Tunnel engineering report that stated "the effect of earthquakes was studied thoroughly" because of its location in a "Zone 3 area."
According to this report, well designed tunnels are generally deemed seismically safer than bridges; and according to professional regulatory and engineering websites, this still holds true, but not if the tunnel is damaged or rests on a fault line.
Our transportation minister cited "a bridge" was "more cost effective" than a tunnel and this could be true when taking in consideration other investment strategies. I noticed on an American website that infrastructure cost effectiveness seemed to favour expensive tunnels over expensive bridges.
One risk factor that did favour bridges over tunnels seemed to be related to air space safety and security. In a transportation tunnel under water, fresh air is supplied by an electrical and mechanical system. An open air bridge would have its own environmental safety concerns.
Brian Britten
