Safety first when it comes to flood hit bridges
Posted on: 10.03.2020
The recent torrential rain which caused havoc in the Sydney basin resulted in a number of bridge closures at different locations across the Wollondilly Shire.
As the floodwaters rose and then fell again, Council staff were closely monitoring the bridges at Menangle, Douglas Park Gorge, Stonequarry Creek, Cobbitty and Blaxland Crossing. All have since been checked and reopened.
When floodwater can be seen on the deck of a bridge, SES, Police and/or Council activates an emergency response to close the bridge and to prevent all traffic from entering the area.
Once the flood waters have receded below the bridge deck, maintenance crews are sent out to remove any debris that has washed up unto the bridge deck and carry out any road surface repairs that may be required. Most importantly, structural condition checks are carried out.
Mayor Matthew Deeth explained, “When the water level drops below the bridge deck, safety is the key concern.”
“The bridge may look ready to reopen, but there is so much more to be done before it can be declared safe,” he said.
When a bridge is fully submerged and the water flow is rapid there are a number of different components of the bridge that can move or be compromised or hit by submerged debris.
The primary structures of the bridge are underneath the bridge and are not seen by the public, including abutments, columns, bearings, retaining walls, railings, girders and embankments.
Water needs to subside enough for bridge inspectors to safely get below the bridge to be able to check if it is in sound condition and can safely bear traffic, including heavy vehicles.
Other stakeholders such as adjoining councils and Transport for NSW may be consulted, as well as specialist engineers, before the bridge can be declared safe and reopened to all vehicles.