Soil transfer technology maximises efficiency on civil sites

Estimations by consulting firm MRA Consulting show construction and demolition waste comprises approximately 40 per cent of Australia’s total waste generation.

That waste typically includes timber, concrete, plastics, wood, metals, cardboard, asphalt and mixed site debris such as soil and rocks.

For many Australian businesses, reducing the amount of construction waste produced onsite is an ongoing challenge. VAC Group is among those striving to buck the trend.

The Australian business specialises in non-destructive digging using hydro vacuum trucks for civil projects that require the identification and location of underground assets and utilities such as gas, electrical, water and communication lines.

These vac-trucks introduce water into the soil to excavate it, producing a ‘liquid waste’, which often needs to be disposed of offsite at a licensed waste facility.

The business has built its own vac-truck units for nearly two decades, specialising in the unique excavation process. Ben Stephens, State Manager – Queensland at VAC Group, says the company is constantly looking for ways to improve its service offering and identified the removal of waste from site as one main area it could improve.

“One of the biggest efficiency issues we’ve identified is the disposal of waste from site. A company can spend a large portion of its time removing the waste and taking it to a facility – a vehicle could take this journey multiple times a day,” he says.

“When we think about some of the major projects in Melbourne – Melbourne Metro for instance – you could have 10 to 15 vacuum units on site. Depending on the site, a vehicle could drive between 60 and 100 kilometres out of the city just to get to a waste facility.”

After nearly a decade of extensive R&D, VAC Group has produced a new and innovative technology that is tackling the issue head on.

The result is VAC Group’s Soil Transfer (ST) system – a new system that maximises efficiency and cost effectiveness while minimising the need for offsite disposal of vacuumed material and the risks and environmental impacts associated with non-destructive digging. Mr. Stephens says it is the first of its kind in Australia.

Rather than produce a liquid waste that requires disposal, the ST unit separates the solid and liquid components of the slurry, meaning the material can be reused on site and minimise the offsite waste disposal process.

The ST device is portable and typically housed on or near construction or civil sites in close proximity to the non-destructive excavation activities.

Mr. Stephens explains that the straightforward process has numerous flow-on effects for site efficiency and costs.

“It’s a closed loop process. The soil transfer technology recycles 100 per cent of the slurry generated by the excavation process onsite – where it was produced,” he says.

Once dried, the solid fractions of the slurry are suitable for fill works such as filling excavations for service location potholes. The liquid fraction of the waste can then be reused for vacuum excavation.
Mr. Stephens adds that fine particles are another byproduct of the process, and are potentially suitable for horticultural applications.

“With soil transfer, greenhouse gas emissions are reduced because there are fewer, smaller trucks making shorter trips to dispose of the same material. This means the trucks are doing the same work but using less fuel,” he says.

Compared with traditional non-destructive excavation projects, Mr. Stephens estimates that the technology and subsequent reduced fuel consumption saves 3960 tonnes of carbon dioxide per ST unit annually.

“The reduction of CO₂ emissions is significant, which subsequently means there are a lot of positive flow on effects for the environment,” he adds.

With fewer trips to take any waste offsite, the use of the ST technology also helps improve work completion cycles and reduce labour downtime.

“A typical vac-truck can only remove a single excavated load per 12-hour shift, which means larger units are needed, more fuel is consumed and more commercial traffic is impacting roadways,” Mr. Stephens explains. “In the same 12-hour shift, our ST system can accomplish four or more loads.”

Mr. Stephens says the first opportunity to showcase the ST system arose last year at the 2017 No-Dig Down Under expo on the Gold Coast. Since then, VAC Group has introduced one ST unit to both the Australian and New Zealand markets, the latter of which he says has gone “gangbusters”.

“We’ve had a lot of positive feedback, especially in New Zealand. A lot of people and organisations have identified it as a valuable asset onsite in ways we didn’t even think of, which gives us plenty of opportunity to evolve the technology in the future.”

VAC Group is also developing fully electric vehicles, which Mr. Stephens says would further enhance the environmental and cost benefits associated with soil transfer.

Looking ahead, he says there’s a lot more scope to introduce more models into Australia in the coming months, particularly as contractors look for more sustainable means to undertake civil construction projects.