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Canberra is a city that loves an acronym and it has already come up with one for the impressive, million-dollar stone wall that is being built along the Cotter Road: GWOC. As in, Great Wall of Curtin. The sound wall may be being built as part of a 21st century road project, but its skill and artistry harks back to another time, each of the estimated 20,000 stones in the structure placed there by hand. Stonemason Richard Taplin, director of Canberra company Cubic Metre, with his team have been working for months painstakingly placing and cementing each rock in the wall. The 650 metre-long wall is being built as part of stage two of the $28.9 million Cotter Road duplication, which also includes a new shared path. It is believed to be the longest stone wall of its kind in Canberra. Transport Canberra and City Services director of capital works, Ben McHugh, said the noise wall had been budgeted at $1.2 million. "The noise wall location really determines the materials," he said. "We've got residents within about 60 metres of Cotter Road and they're hard to pick up because of all the trees. But trees aren't an effective way to manage noise, the noise just penetrates through the vegetation. "When we did the design, it was identified with the increased traffic volumes that are going to come on Cotter Road, it was going to exceed the noise levels and we needed a noise wall. "The best way to mitigate noise is to get a wall as close to the noise source as possible; road noise generally travels outwards and upwards. "So the further away you go with a noise wall, the higher the wall has to be because the noise is just going to travel upwards. So closer to the road the better and you have to design it to be safe." The approvals process for the wall went through the National Capital Authority because of Cotter Road's proximity to Government House and its location on designated land. "This kind of stone work is coming back and being more common around Canberra because roads that were built 30, 40, 50 years ago by the NCDC are starting to be duplicated now and those roads had a lot of the original stonework along them," Mr McHugh said. Mr Taplin said about 700 tonnes of rocks came from a quarry at Wee Jasper to do the wall, his team working since last October and due to finish both sides by March. "It's done all by hand. You basically place the stone in the mortar bed and then backfill it with more mortar behind and we've also got brick ties to tie it into the wall," he said. "It'll last a long time, it's not going anywhere." Huon project manager Bojan Knezevic said 140 walls had been dug six metres deep to also support the wall. About 1000 cubic metres of concrete was used in the wall and its foundations. Mr Taplin said he was never daunted by the job. "When you first look at it you think, 'Woah, there's a far way to go' but we just did it in sections," he said. "We feel really proud of it." Mr McHugh said the wall would be long-lasting and require little ongoing maintenance, not least because it was not likely to attract graffiti. Perspex screens had also been used in sections close to the equestrian parade grounds to allow in light. They were opaque to ensure horses were not spooked by the traffic. Cotter Road carries about 25,000 vehicles a day but was expected to carry about 35,000 vehicles a day with the growth of Molonglo. Stage one of the Cotter Road duplication was finished three years ago.

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