Sustainability in Geotechnics

7 June 2024

In September last year, our colleague Emma Pike posted about the Ground Engineering Sustainability conference that she had just attended.

As can be seen from our website, sustainable principles underpin all that we do at CampbellReith. We know that we are ideally placed to influence, champion, and deliver sustainability commitments within the Built Environment and we have always taken this responsibility extremely seriously.

In the geotechnical team, we have been reflecting about our contribution and thought, how much more sustainable can you get that turning former landfill sites into spaces for high quality housing using best practice and innovative techniques to minimise the carbon footprint?

We are currently working on two such schemes and are just about to start on a third. Among the sustainable practices we have brought to the projects are:

Setting appropriate development levels
Early involvement in these and other sites allows us to work with our civil engineering team to agree development levels that maximise the cut and fill balance and reduce excess volumes that require to be disposed of or imported. Working closely with our civil engineering colleagues also allows the use of gravity drainage to be maximised and addresses issues of accessibility at building thresholds and at junctions with surrounding areas.

Desk study and review
At both sites, we were appointed after initial site investigations and ground treatment designs had been completed. We undertook detailed reviews, supplemented by our own desk study research and, in some cases, further intrusive investigation, to identify were more refined or efficient solutions might be achieved. As ground investigation has its own carbon footprint, we prepared a matrix looking at the potential areas for reductions in the carbon footprint, the likelihood of refined solutions being workable, and the benefits when weighed against further investigation.

Reducing concrete in foundations
At one site, piled foundations were prohibited and at the other, piled foundations were proposed for the structures and primary infrastructure. At the former, which has up to 25m of landfill and highwalls around the perimeter, this posed a significant constraint to development. Detailed analyses by our geotechnical team showed that the combination of an engineered earthworks platform with raft foundations is adequate despite the thickness of the fill. At the other, detailed and informed discussions with regulators (the highways authority, water company and other stakeholders) allowed pragmatic performance criteria to be agreed in respect of total and differential settlement. We designed a surcharging scheme using site won fill which has treated the ground such that the infrastructure is being constructed without special engineering measures. The landfill here is up to 18m thick.

Pragmatic and responsive design
The presence on site of a full time ER has allowed us to witness first hand the effectiveness of treatment originally specified and given us the confidence to amend the specification where savings to materials and programme can be realised. This has included analysing ‘as measured’ soil stiffnesses to allow surcharging requirements to be reduced. It also allowed us to accept a proposal to reduce double handing (lifting, sorting, replacing and compacting) by having enhanced inspections. This has saved time, money and, importantly, emissions from plant.

As our colleague Sam noted in our previous article, we work very closely with our Land Quality team who also made huge contributions to making these projects more sustainable. In both cases, this included the omission of a horizontal gas venting layer, as well as a vertical barrier around one of the sites.

If you are looking for technical support in the sustainable development of a brownfield or otherwise complex site, get in touch!