Dealing with large-scale infrastructure projects in Melbourne has led to a need to minimise disruption by using non-destructive digging, but this approach is prompting new and innovative solutions to clean up the resulting waste.
From Melbourne’s M80 Ring Road Upgrade to the Metro Tunnel project and the Hoddle Street widening – the prosperous growth of the city is effervescent.
While initial works mean more truck movements, excavations and disposals and minor disruptions, in the case of the Metro Tunnel, the end result is freed up space on the city loop, more trains across the state and a less crowded and more reliable train network.
Ensuring all of these works are completed in a timely manner rests with the hard working construction companies and their various contractors. To reduce disruption to amenities, many of these companies are turning to less invasive methods of construction and disposal, including non-destructive digging (NDD).
NDD is a way of safely excavating underground utilities such as pipes and cables to minimise damage and disruption. It is also used for service locating, water, gas electrical infrastructure renewal and soil investigations. However, despite the benefits over traditional excavation, NDD presents a new set of challenges in dealing with the waste as it arises in liquid/slurry form.
That’s according to Repurpose It’s George Hatzimanolis, who says that dealing with a liquid waste such as muds or slurries from hydro excavation waste is a very different proposition than dealing with excavation waste that is spadeable and dry.
“There are numerous challenges when handling hydro excavation waste, such as appropriate containment and water run off management, as well as ensuring that fit-for-purpose plant and equipment and trade waste agreements are in place to dewater the material prior to processing,” George says.
The EPA’s regulations around NDD are covered by its Industrial Waste – Classification for drilling mud. According to the document, drilling mud may comprise a mixture of naturally occurring rock and soil, organic matter and water and drilling fluid.
It notes that prior to commencing drilling or excavation activities, the waste producer must undertake a document assessment to demonstrate whether contamination could be present, and if so, then the site is to be managed as contaminated.
To process the hydro excavation waste and solve the challenges of tomorrow, Repurpose It is building a construction and demolition washing plant in Epping in Melbourne’s north. The plant will include an advanced water treatment system with a triple interceptor system and trade waste licence with Yarra Valley Water. The facility will be purpose-built to handle hydro excavation waste, with the materials delivered in sealed vessels and dewatered prior to the sludges being processed. In the washing plant, valuable resources such as sand and grit will be removed and converted to materials to onsell to the construction industry.
“The plant will deal with this growing waste stream in a best practice environment that manages the environmental risk, while obtaining the highest amount of resource recovery rates as possible to convert the material back to a resource for the construction industry,” George says.
As part of this, Repurpose It has partnered with Rangedale Drainage and Civil Services who work with various contractors around Melbourne. With more than 100 staff working 24 hours a day, seven days a week, the family-owned business has 24 non-destructive digging trucks working day and night on Melbourne projects. Rangedale is working on projects such as the M80 Ring Road Widening, Metro Tunnel and West Gate Tunnel projects.
Neil Kermeen, Managing Director of Rangedale Drainage Services, explains that its 24 trucks could produce up to 400 cubic metres of non-destructive digging slurry each day. In addition to the trucks, Rangedale also has five semi-vacuum tankers with a capacity of about 25 cubic metres per truck performing three to four loads per day – generating a significant amount of NDD slurry.
“About 50 per cent of this is prescribed slurry. This is a categorised product that has to be transported and disposed of so we needed a licenced EPA facility,” Neil says.
“We currently have a lot of difficulty in finding licenced disposal sites that can handle the capacity and therefore for us to team up with Repurpose It is a given to fix this problem.”
Neil adds that this includes Category A, B and C prescribed industrial waste while Rangedale Drainage Services has its own recycling plant north-west of Melbourne’s CBD in Keilor East for clean slurry. He says that all of its prescribed industrial waste will go to Repurpose It at its Epping site.
Neil says that having a resource recovery strategy is of particular importance for Rangedale as it forms part of their tendering process.
“For example, with the West Gate Tunnel Project, it’s of major benefit for our clients to know that the material is going to a major resource recovery project.”
He says that because its vehicles are vacuum trucks, Rangedale is able to prevent any water run-off and dispose of the materials safely.
George adds that Repurpose It’s washing plant will be particularly crucial as new waste streams come online into the future. The washing plant will wash materials which include rail ballast, glass, excavation materials and demolition waste fines.
“New waste streams present challenges, but also opportunities as businesses invest in technologies to deal with the waste of tomorrow,” George says.
“If this waste doesn’t go to a facility to be dewatered it’s either landfilled or going to a paddock. That’s partly because of the volume of material and the lack of infrastructure to deal with it, which is why we’re investing in capacity not just in Melbourne’s north but across the city.”
George notes the EPA is updating its regulations around NDD with new waste streams being generated.
He says Repurpose It is following this closely to ensure the material is classified and disposed of according to current regulations.