Potholes not caused by rain alone, says senior engineer

Poor maintenance: rain is not the cause of potholes, says a senior engineer, but rather bad preparation of roads. Photo: Kate Healy.
Poor maintenance: rain is not the cause of potholes, says a senior engineer, but rather bad preparation of roads. Photo: Kate Healy.

They’re the bane of every driver: burst tyres, cracked rims, damaged alignments or worse.

Potholes in our Ballarat roads are blamed on rain, but in fact it’s vastly increased amounts of traffic, poor roadbase preparation and ad hoc solutions that are the main cause of road damage.

A senior civil engineer with more than 50 years of road-building experience, said while potholes are inevitable, strategies and proper planning could limit their numbers drastically.

“The three fundamentals of constructing a road are drainage, drainage and drainage,” said the engineer, who chose not to be named.

“I could build a pavement 100mm deep, seal it and carry as many semi-trailers on it as you like. It depends what is underneath the pavement, the sub-grade, and how well it’s prepared.”

Some of the worst potholes are appearing on roads now subject to heavy use by semi-trailers and B-doubles. Increased traffic loads and high-repetition trips, where trucks make journeys back and forth consistently over an extended period, damage road seals rapidly and allow water ingress.

Widening roads to stop edge deterioration, as has been suggested by council, is no solution.

“Edge maintenance has nothing whatsoever to do with potholes, which are the result of poor road preparation,” said the engineer.

“If you widen a road, vehicles will simply use more of the road to avoid potholes and cause further damage.

“If you do get potholes, and you will, then they must be patched correctly. You need to ‘bellmouth’ the pothole: excavate back around the edges and flatten the hole base. Simple ‘throw and go’ fills won’t last any time. 

“The bottom of the hole needs to be made bigger than the top. But it seems we don’t have time to do these jobs properly these days. It’s all about reducing costs.”

A Canadian student’s science experiment using chicken feathers mixed with asphalt has reduced water ingress into potholes – a paltry cost, it would appear.

The Courier, Ballarat