Strategic approach to soil management

Project summary

The strategic approach to soil management was an innovative way of approaching the large volumes of soil excavated across a portfolio of build sites owned by Barratt David Wilson (BDW) Homes. The project reduced the volume of soil excavated, and through identification of surplus and careful stockpiling, was able to reuse the majority without resorting to landfill for disposal.

The background

Sustainable management of soils in construction is a frequently overlooked opportunity when developing residential land, often resulting in suitable but excess materials being unnecessarily sent to landfill for disposal.

BDW recognised that a strategic approach to materials reuse across the development portfolio was needed and that this would both bring commercial advantages and reduce the environmental impact of the business. The issue had been identified as a potential £20 million risk item, assuming no reuse of materials and disposal off-site as non-hazardous at an inert waste receiving facility.

RSK Geosciences has been supporting BDW across the company’s development portfolio for several years, providing geoenvironmental and geotechnical consultancy works. After a high-level review identified significant opportunities for reuse of top- and subsoils, a strategic approach to soils management and reuse was created with the RSK Geosciences team.

The challenges

Awareness of waste legislation, waste duty of care responsibilities and opportunities for reuse of soils in construction, while improving, remains low. There are many examples across the residential development sector where the Definition of Waste: Development Industry Code of Practice (DoWCoP) has been incorrectly applied, potentially exposing developers to enforcement by the Environment Agency.

To achieve success, two key requirements were identified: staff buy-in and willingness to engage and support the strategy, and easily referenced ‘live’ information on what materials were stockpiled across the portfolio.

The solutions

Engineers from RSK Geosciences, in conjunction with the BDW technical manager, initially delivered a series of meetings and events, both in person and online, to raise awareness for those at BDW unfamiliar with the legal requirements relating to waste soils, waste duty of care and materials reuse. The training focused on the organisation’s responsibilities as a waste producer, the waste hierarchy and opportunities associated with legitimate reuse of materials using DoWCoP.

The materials register is an MS Excel document accessible to both BDW and RSK Geosciences staff. This is updated at monthly meetings and as new information comes to light or new sites come online.

The strategy follows the waste hierarchy with the following priority:

1. designing out the need for excavation (prevention)
2. identification of surplus soils in a development (reuse)
3. implementation of effective stockpile and material management (minimisation/prevention)
4. consideration of excess material during foundation design (minimisation/prevention).

A review of available information undertaken on pre-purchase sites further highlighted areas where excavation of soils could potentially be prevented and to identify whether the site being considered for purchase could act as a potential donor or receiver site, and how this would fit in with wider material requirements of sites across the property portfolio.

The impact

The team used the CReDiT Earthworks tool developed by RSK Geosciences and the University of Surrey to identify the tonnes of equivalent carbon (tCO2e). This is calculated to have saved 5055 tCO2e to date, with a further 18,400 tCO2e forecasted to be saved from the planned future reuse of soil.

To date, a total of 84,800 m3 of topsoil and subsoil has been reused and therefore diverted from landfill, with an estimated 213,700 m3 of material currently identified for reuse on sites in the coming years.

While it may seem an obvious solution to share material between sites, it is not common practice in the industry.

The successful use of the strategic soil management approach shows that, with a collaborative approach and buy-in from all stakeholders, sustainable use of materials across a property portfolio is possible. The approach is already being rolled out in other BDW regions as a direct result of this project’s success.