Environmental News

Industry calls for better spoil management

The New South Wales Government has invested in a number of new tunnels designed to relieve traffic congestion in some of Sydney’s busiest areas. These include the North West Rail Link, which will involve twin 15km tunnels from Bella Vista to Epping, the proposed 9km NorthConnex tunnel motorway linking the M1 and M2 motorways between Wahroonga and West Pennant Hills, and approximately 19km of tunnels associated with the WestConnex urban road project.

However, it appears the situation may become worse before it gets better, with projected figures indicating there will be a significant increase in truck movements during the tunnels’ construction as spoil is transported away from the project sites.

According to a report by The Sydney Morning Herald, over the next eight years the projects will collectively generate approximately 10 million m3 of spoil, equating to about 600,000 truck loads and 1.2 million trips across the city.

Construction engineer and northern Sydney local Chris Jones told The Sydney Morning Herald that the spoil across the tunnelling projects was not being effectively co-ordinated by the state government.

“They’re [the tunnel projects] designed to relieve Sydney’s traffic but on the way to that objective, have they [the NSW Government] looked at whether it will compound the problems for traffic we get there?” Jones was quoted as saying. “It is apparent that nobody is looking at these issues.”

Jeff Burns, principal of NSW-based urban planning and economic advisory firm Environmental Property Services, agreed, telling Quarry that there appeared to have been a lack of integration between the planning of the projects with respect to their lead times.

“The planning process for major projects like these takes about two to three years, which should enable a better investigation of spoil destination opportunities,” he said.

Alternative transport options
A number of spoil transport options have been proposed or implemented in the past that have either reduced or removed the need for additional trucks on the road.

As previously reported by Quarry, Jones is part of the QFill joint venture that earlier this year proposed a new 2km tunnel to transport NorthConnex spoil to fill the disused Hornsby Quarry. In addition to removing haul trucks from Sydney’s busy motorways and moving them underground, it was said that the proposed tunnel could later benefit the community as a permanent two-way road link between the Hornsby CBD and the freeway.

Jones said the QFill proposal originally involved a smaller tunnel and a conveying system similar to the one used to transport spoil from Brisbane’s Legacy Way tunnels to the Mount Coot-tha Quarry in 2012. {{image2-A:R-w:300}}

Alan Robertson, director of consulting firm Ausrocks – which was engaged to complete the conceptual designs for spoil placement in the Mount Coot-tha Quarry – told The Sydney Morning Herald that while it was initially believed that transporting the Legacy spoil by truck would be the easiest option, the 4km conveying system ended up being an unmitigated success.

“There were 100,000 less truck cycles (round trips) for trucks on the local roads as the conveyor system ran directly into the quarry, there was a significant reduction in greenhouse gas emissions for the conveyor transport and radial stacker placement compared to trucking, and to fill the invert to provide the final road surface, the conveyor system was reversed to run screened spoil material back into the tunnel, once again maximising the use of the excavated rock and eliminating the need to truck material into the site,” he explained.

Commenting on the economic feasibility of using a conveying system for spoil transport, Burns told Quarry, “There are obviously associated costs but I think the economic cost for the project in using the system needs to be considered against the economic cost to the broader community of using the existing road transport network.”

However, while Burns said conveyors were effective over short distances, he pointed out that they would not be able to solve Sydney’s long haul distance transport problems, citing another opportunity the state government had not properly investigated.

“I think Sydney is underutilising the freight rail network,” Burns explained. “The city has a freight rail network that’s capable of transporting large volumes of this type of material and I think that what Sydney is lacking is a depot that enables placement of this type of material from a rail hub.”

Echoing the sentiments of others in the Sydney community, Burns added that he believes that when it comes to spoil management, increasing truck movements is “never the right answer”.

More reading
Quarry tunnel a ‘golden opportunity’
Legacy Way: solving a materials handling challenge
Legacy rock spoil conveyed to quarry

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