VERONA ISLAND, Maine — Drivers seeking to cross the Penobscot River on Route 1 and Route 3 were taken by surprise last month when ice that had accumulated on the cables of the Penobscot Narrows Bridge began to melt and fall in large chunks onto the roadway. After at least four cars were damaged by the ice, authorities closed the bridge, sending some motorists 40 miles out of their way.
Though it was the first time the issue had happened to this bridge, which was completed in 2006, bridges of this type from Vancouver to Sweden have experienced the problem. Multiple fixes have been suggested and, in some cases, implemented, but engineers say there is no easy answer.
“Right now there is no silver bullet solution for this,” said Richard Martinko, director of the University of Toledo University Transportation Center. Martinko lead a team of researchers to investigate solutions to the icing problem after the Toledo Skyway Bridge had to close temporarily due to falling ice.
Like the Penobscot Narrows Bridge, the Toledo Skyway Bridge is a cable-stayed bridge. The deck of the bridge is held by cables, which are attached directly to the bridge’s towers. The Uddevalla Bridge in Sweden, the Port Mann Bridge near Vancouver and the Zakim Bridge in Boston, all cable-stayed bridges, have also had to close because of falling ice.
“Heating the stays, blowing hot air on the stays, chemical solutions,” Martinko went on, “have all been tried and have not been successful.”
In order to study the conditions on the Toledo Skyway Bridge, sensors were installed on the cables which transport information about the conditions on the bridge to authorities at the Ohio Department of Transportation.
Martinko said the DOT can predict when ice buildup might occur, and when it might drop, so traffic can be redirected ahead of time.
In another attempt to curb the problem, authorities in British Columbia announced last January that cable sweepers would be installed on the Port Mann Bridge in Surrey, according to local news reports. These mechanisms fit around the bridge’s cables and are lowered and raised in order to prevent ice from accumulating.
Engineers from the Maine Department of Transportation have examined these technologies, but for now will stick to using the weather station, located at the bridge, to monitor conditions there.
“We have a presence [at the bridge] and the weather service has been very good,” said John Buxton, the state bridge maintenance engineer. “At this time, we’re going to rely on that.”
He said implementing one of the mechanisms described above would not be worth the cost.
“I don’t anticipate this to be happening on a regular basis,” he said, referring to the Christmas ice storm.
He added, “If it starts to be a regular occurrence, then we’ll have a more aggressive approach.”