Yesterday, the Lismore App updated you on the latest road news for the Lismore Local Government Area (LGA).

One of e the biggest criticisms of Lismore City Council has been the recurring potholes over a wet three-year period and how some roads wear very quickly after being resurfaced.

This story gets more technical, so you can understand the road-rebuilding process post-flood.

ASPHALT V BITUMEN SEAL

You will have noticed two distinctly different types of road surfaces across the Lismore LGA.

Firstly, you have the very smooth asphalt surface and then the more stone-like bitumen seal.

The two surfaces all depend on budget. The smooth asphalt is the Rolls Royce of roads, your gold standard (like on Molesworth Street), while the stone-like bitumen seal is driving your everyday Corolla. A great car in its own right but not the ride of a luxury car (as Richmond Hill Road will be).

When you see a smooth asphalt surface, you know that grant funding was large enough to complete the project. On the other hand, when you see a stone-sealed road, you know that the funding needs to stretch as much as possible to fix the entire length of road. The alternative is to leave part in a substandard way while putting down the gold road for a section.

"This is a better outcome for the community as it gives best bang for buck," said Brendan Logan Chief Operating Officer of Lismore City Council, the man in charge of rebuilding Lismore's infrastructure assets including the road network.

"So, if you take our Richmond Hill Road project, we've got somewhere between $2.2 and $2.7 million to do the project and if you put asphalt down, the length of the road you can fix or make better is limited. But, we can stretch that money out and still put massive improvement on the service surface with a bitumen seal."

The design life of a road is projected to be 30 years. Mr Logan explained that it is not the surface of the road that matters most but what is under the surface that determines the lifespan of a road.

HOW IS LCC FIXING OUR ROADS?

Steve Bennett is one of the lead project managers for Lismore City Council. We asked Steve to explain the road fixing process so Lismore App readers could understand what is being done.

"We've got a stabilised sub-layer, where all the cracking is, and below that you have the sub-base layer."

"So, our treatments for Union and Richmond Hill, we basically profiled out at least half of the stabilised layer. Then we treated the sub-base layer with slag lime which is incorporated with a stabiliser machine, and then we added a brand new layer of base material over the top.

"This basically changes the characteristics, so chemically wise it changes how the material reacts, it makes it stronger. It makes it less permeable to moisture, which is certainly what we wanted down at Union and Richmond Hill with the drainage issues and the moisture coming out of the ground there.

"It enables us to reuse existing pavement as opposed to having to remove it, which is a lot more earthworks and a lot more waste. So this way, we get to improve it and keep it essentially, so it does reduce the costs and is obviously a bit more sustainable.

"Then we've got brand new base material, which we use from Blakebrook quarry.

POTHOLES

The comment that you see regularly on social media pages after a road is resurfaced and a pothole appears in the first 6 months, is that council did a lousy job fixing the road. Steve explained how potholes are formed.

"Essentially what can happen is the bitumen spray seal can get removed, whether it be through a car skidding or whatever, but once that the bitumen is removed, you're basically back to the bare pavement. So once that gets wet, waters ponding on it, you get the action of the traffic and it just plucks the stones out."

"Once one stone is plucked out, the next one plucks out and the pothole just forms and develops. Whilst it's doing that, you've got ponding water, so you got water saturating into the payment."

"That's the whole point of the bitumen spray seal, to keep it waterproof. You're trying to control the moisture from underground with subsequent drainage and then you've got the bitumen spray seal at the top that controls the water that protects it from above."

Steve mentioned that burnouts or even road skids to avoid an accident if you are following too close to another car, will remove the seal making it more vulnerable to damage once again.

"The first few days after a seal is probably the worst time because the seal penetrates into the pavement, that's what gives it the bond. So, that's still developing, especially after a hot day straight after a new seal, it's still a bit lively, it's still setting if you like, so it can be quite sensitive."

Richmond Hill Road has an added problem with sections affected by an underground spring that has water making its way to the surface causing cracks and eventually potholes.

"We have created a rock drainage layer, so basically 300mm of what we call an E-5, so a rock that is between 75mm and 150mm in diameter that's all wrapped in geo fabric material."

The water comes up to the rock drainage layer that shapes across floors and allows that moisture to travel in the rock through the voids and basically just provides a separation layer between that and the actual pavement layer. So, the pavement layer then goes into your sub-base layer and the base layer is built on top."

Fixing roads in the Lismore LGA is difficult, especially with our famous 'pug' soil, a clay-based soil that results in a lot of movement depending on the weather. So, road users can do their bit to keep our new roads in better condition longer.