Don't dig yourself into an unsustainable hole
Riccardo Wong* from CDEnviro discusses how, with the economic and infrastructure boom in Australia, the onus to develop and build new infrastructure responsibly, as well as profitably, should be top of the agenda — starting with excavation.
The G20 recently identified infrastructure as one of the key drivers of achieving SDGs (sustainable development goals). The focus has been on climate change and achieving sustainable infrastructure development without carbon-intensive activity. However, wherever you are in the world, infrastructure building also requires sound thinking regarding waste management in terms of mitigating soil pollution, minimising disruption to the daily economy and profitability of the city in question.
In July 2019, it was reported that the Australian Government is under pressure to bring forward the implementation of key, long-awaited infrastructure development. There’s an urgent need to reduce congestion on highways, rail lines in NSW and ring-roads in Queensland, among other projects. As the Reserve Bank calls for urgent action in releasing funds to commence some of this $58 billion worth of building projects and jump-start job creation, there’s a big dig coming — so will it be executed in line with SDGs?
Sustainability starts from the ground up
There have been key discussions about what the face of sustainable infrastructure development looks like. At a recent Future Cities Roundtable, the Commonwealth Bank’s Managing Director for Future Cities, Institutional Banking and Markets, Michael Thorpe, indicated that it’s a good time to invest in and create cities that truly meet the diverse needs of the population. Thorpe focuses on the relationship and interdependence between commercial real estate, economic and social infrastructure, sustainable financing and technology. However, no one really discusses sustainable aspects of manifesting these aspirations environmentally, which if undertaken properly also contribute to the longevity of sustainable practice. As far as CDEnviro is concerned, sustainability starts from the ground up.
Non-destructive digging, or NDD, is a less invasive/non-destructive approach of excavating earth in a controlled manner. It is a quicker, much more effective and generally safer method of excavation.
In the throes of all the proposed infrastructure works, non-disruption of the public’s existing lives and activities will be of significant importance. People still have to travel — getting from A to B cannot be unnecessarily impaired if at all possible. Local economies will count on that.
While NDD is more discreet and controlled, the main by-product and disposal challenge is the mud waste produced. Even if it is accepted at landfill sites, the costs to dispose of it are prohibitive as it weighs so much because it is waterlogged. Furthermore, the content of the mud may include contaminants which, if not removed, may leach into the surrounding soil and cause untold environmental damage. However, this is where we scrutinise differently to find the positive opportunity in this conundrum rather than purely the disadvantages.
Creating unlikely revenue streams
As environmental legislation becomes more stringent, recoup and re-use will become more desirable as the payload per truck will be reduced.
The leftover NDD mud also contains a lot of useful, re-usable materials that can be recycled and made available for resale. Thereby, a new revenue stream is created, turning what might be perceived as a loss into a potential profit. This is more of a circular economy approach, which contrasts with the traditional linear approach of extract, use and dispose.
There are tailored solutions available such as bespoke reception centres for processing hydrovac waste and recovering sand, stone and organics to produce independent revenue streams. Technology also allows for thorough dewatering of the final clay content to ensure easy, and much less expensive, disposal.
The capability exists to cater to a wider range of more challenging and more lucrative waste streams. For heavily contaminated waste mud, it’s possible to remove heavy metals and hydrocarbons from the wastewater stream as well.
Screening and scrubbing material ensures effective removal of contaminants, density separation, attrition and high-pressure washing, resulting in clean and separated stone, sand and organic material, primed for re-use. As well as creating these revenue streams, the cost savings on transport and disposal are huge, meaning that businesses who invest in treating hydro excavation wastes are earning and saving simultaneously.
As Australia braces itself for the start of its massive infrastructure drive, discussions about sustainability should really permeate every part of the process. The desired end results for the users are only really valid if the entire exercise has sought and followed sustainable practice throughout.
This is where the construction and engineering sectors can really make a difference. We must look for opportunities to work smarter, more efficiently and more cost-effectively, and become ‘circular economists’ in the way that we rebuild our cities.
As a result, the infrastructure industry is afforded greater control of its waste using sustainable means, reducing disposal costs as well as transportation time and resources.
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