Marc Perry (pictured above left) is principal geoenvironmental engineer and Tom Henman is sustainability director at RSK Geosciences
Soil is an undervalued and finite resource. At government level, its importance is somewhat understood and recognised alongside the benefits of carbon reduction, waste reduction and the delivery of biodiversity net gain (BNG). There are real opportunities to make better use of soil but these need to start in advance of contractors mobilising to site. It is up to the construction industry, and specifically designers and contractors, to deliver on the potential to increase development sustainability. Achieving this may require a change in the way we design and construct our built environment, including housing developments, commercial schemes and infrastructure projects.
To protect soils as a resource requires consideration at project inception rather than being left to the implementation stage – by this point, the ‘big wins’ have been lost. Also, once soils are excavated and stockpiled, they become classified as a waste and can then become a problem rather than a valuable resource.
“It’s disappointing that the current National Planning Policy Framework consultation doesn’t take the opportunity to examine soil use and reuse”
Development works inevitably result in the excavation, movement, stockpiling and placement of soils, with the potential for waste soils to be generated, and soil function and carbon to be lost. This may be unavoidable due to contamination, but often it is down to a lack of planning.
An assessment of the resource potential and soil quality at an early stage is highly beneficial. It can be considered as a factor in the design of the site layout and levels to retain as much quality soil as possible and avoid its disturbance. This supports waste prevention and minimisation, the highest-priority elements in the waste hierarchy.
If soils can’t be retained or reused on site, the next step is to consider reuse offsite. Here, early stage assessment is also key because if this is done before soils are excavated and used elsewhere as a resource, they never become ‘discarded’ and waste legislation does not become a factor. In our experience, this approach can yield significant benefits, especially when considered over a portfolio of sites, where some may have an excess of soil while others have a shortfall.
Costs pile up
Generating unnecessary waste is hugely costly to contractors, from waste classification and testing to haulage, gate fees and landfill tax charges. There are also associated environmental impacts: carbon emissions and environmental nuisance from extra lorry movements. This is compounded where virgin materials have to be brought in to make up for the lack of suitable soils.
The government has set a target for significantly increasing housebuilding, with 1.5 million homes planned over the next five years. There are challenges and opportunities ahead, with a continuing focus on brownfield land, as well as ‘greybelt’ plots within the greenbelt, hopefully bringing forward remediation and regeneration. These new developments will need to be supported by a raft of infrastructure projects with improved or new roads, utilities and urban centres. This presents a significant opportunity to achieve more sustainable development and benefits to nature through BNG. It’s disappointing that the current National Planning Policy Framework consultation doesn’t take the opportunity to examine soil use and reuse in the construction sector to help meet these goals.
So how can contractors help? By requesting from clients what information is available in terms of soil-resource assessment and upfront design work to support soil retention and reuse. Identifying materials suitable for reuse on or offsite before excavation is key to this.
Perhaps even bolder steps are needed, led by contractors fully embracing net zero across the supply chain and construction phase, recognising and being accountable for embodied carbon, setting measurable and ambitious targets, and identifying step-change opportunities for bigger wins. This is not just the right thing to do to achieve more sustainable development, it will increasingly be something that clients require of contractors in the drive towards net zero.
