FILE IMAGE. Nicole McDougall

'Extreme' danger rating on two CQ bridges

WEIGHT restrictions have been imposed on two Livingstone Shire bridges after engineering inspections found them at extreme risk of structural failure.

Detailed investigations were commissioned for bridges on Doonside Rd and Werribee Rd which found structural failure was a likely outcome which could result in "major consequence in terms of serious injuries and major loss”.

This meant the bridges were slapped with an 'extreme' risk rating.

While strengthening and replacement strategies will be considered in the long term, load restrictions were recommended in a report presented to Livingstone Shire Council yesterday.

However, the report also noted council could face "a backlash from property owners in the vicinity who are impacted by longer travel distances (and therefore by higher costs)”.

The Werribee Rd Bridge is a single span timber girder bridge crossing Shannon Creek, a permanent non-tidal waterway.

The bridge's cast-in-situ concete abutments were built in the 1960s, but no formal designs could be tracked down.

It is estimated less than 500 vehicles use the bridge annually and gravel approach roads were found to be in moderate to poor condition.

Both structures and the roads approaching them are historically unusable during flood events or heavy rainfall and can remain impassable for extended periods once inundated.

Werribee Rd is regularly used by light vehicles, semi-trailer cattle trucks, rigid cattle trucks and semi-trailer logging trucks to access HQ Plantations.

"The risk of these heavy vehicles damaging the bridge, or causing the bridge to fail is high, given the unknown bridge capacity,” the report concluded.

Inspections found a load limit of 12 tonnes should be immediately implemented, along with restriction of usage to rigid trucks until other measures are put in place.

Doonside Rd bridge crosses Hedlow Creek and is also used by less than 500 vehicles each year.

Precast concrete deck planks were installed in the 1990s and temporary steel mid-span props were installed in the early 2000s by Roadtek, but no formal desgins are available.

This bridge provides access to one property and is regularly used by light vehicles, semi-trailer and rigid cattle trucks hauling cattle to and from the property.

As with Werribee Rd, the risk to these vehicles is high.

It was recommended a load limit of 6 tonnes be implemented immediately, with similar restrictions to rigid trucks.

Both bridges could be demolished and replaced.

Councillors requested the infrastructure services department investigate suitable options for the two bridges and prepare comparative cost estimates.

Further information about the restrictions will be published on the Livingstone Shire Council website.