What we do Soil resource, MMPs & waste

Soil resource & soil management plans

Some local authorities now require a Soil Resource Survey prior to any earthworks operations and to inform the materials and / or waste management plan submitted with the planning application.

In the context of greenfield development, a Soil Resource Survey essentially establishes the quality of Topsoil and Subsoil.

A Soil Management Plan sets out the correct procedures for topsoil stripping, stockpiling and placement as well as subsoil preparation.

Lithos can draft Soil Resource Surveys and Soil Management Plans as separate documents or include the information within a broader Site Investigation or Materials Management Plan. An example of what we do can be found here in our Case Studies.

Soil is a fundamental and ultimately finite resource that fulfils a number of functions and services for society which are central to sustainability. Some of the most significant impacts on this resource occur as a result of activities associated with construction activity, yet it appears that there is a general lack of awareness and understanding of this need within the construction industry.

A Code of Practice (CoP) has therefore been developed by Defra to assist anyone involved in the construction sector to better protect the soil resources with which they work.

Several Local Authorities around the UK require a Soil Resource Survey as part of planning, within the Yorkshire region, under their Local Area Plan, Wakefield Council require a Soil Resource Survey for all greenfield sites.

Even if not required for planning, by following the guidance in the CoP you will not only be able to help protect and enhance the soil resources on site but you may also achieve cost savings during development. Topsoil and Subsoil resource information may also be required by the ecologist for habitat creation for Biodiversity Net Gain planning and also the landscape architect when considering suitable planting post development.

Under the Defra CoP the Soil Resource Survey should be carried out by a suitably qualified and experienced soil scientist or practitioner (e.g. a member of the Institute of Professional Soil Scientists). This is not the same as a geotechnical report or contamination survey which should not be relied on for detailed information on Topsoil or Subsoil resources.

The Soil Resource Survey will involve inspection, sampling and testing of the Topsoil and Subsoil at the site to determine soil properties such as nutrient values and soil texture. Identification of topsoil and subsoil resources is also necessary as part of a construction site’s Site Waste Management Plan or Materials Management Plan) as most greenfield developments generate surpluses of topsoil.

Once Topsoil and Subsoil resources have been characterised in the Soil Resource Survey a Soil Management Plan should be prepared as a defined sub-section to a MMP and may be factored into the SWMP, detailing how the resources will be managed.

Material Management Plans (MMPs)

Off-site disposal of surplus clean naturally occurring soils to landfill is not recommended. Any excess clean, natural soil arisings should be suitable for Direct Transfer to another development site, in accordance with the CL:AIRE Code of Practice (CoP), for use either as clean cover material, or bulk fill, without the need for waste legislation to be applied.

The CoP sets out good practice for the development industry to use when assessing on a site specific basis whether materials should be classified as waste or not.

The CoP can be applied to projects where any of the following are proposed:

The re-use of both natural and made ground soils on the site from which they have been excavated (the Site of Origin scenario)
Import of clean, natural soils from another development site (the Direct Transfer scenario), or
Use in of material that has been excavated from another site, following treatment at an authorised Hub site (Cluster Project scenario)

Use of the CoP requires a Materials Management Plan (MMP) which documents how all of the materials to be excavated during the proposed site preparatory & remediation earthworks will be dealt with.

For simple, Direct Transfer scenarios, Lithos can complete the CL:AIRE MMP Form which requires answers to 26 questions, following review of the relevant documents (including Site Investigation & Remediation Strategy Reports).

Lithos can also draft more detailed MMPs for brownfield sites where preparatory earthworks require adoption of the Site of Origin scenario. However, the appointed earthworks Contractor or the design Consultant will need to undertake some earthworks modelling, with reference to proposed FFLs, in order to determine anticipated volumes of cut and fill. The appointed earthworks Contractor will also need to provide information regarding his proposed method of working; i.e. annotated drawings showing the different excavation areas, stockpile locations etc. Consequently, Lithos need to work closely with the appointed Contractor.

Lithos can perform the role of Qualified Person (QP), although it should be noted that we cannot act as the QP for projects where we have undertaken the site investigation, and/or prepared the Remediation Strategy

Waste soil classification and waste coding

Disposal of the made ground off site is not generally considered appropriate, economically viable, nor in line with current Government philosophy regarding sustainable development. However, disposal to landfill (or an appropriate soil / aggregate transfer station) may be the most practical solution for some excess arisings generated by excavations for foundations and sewers, if redistribution and retention on site is not feasible.

Waste classification is a duty of care requirement for the waste producer and all waste must be classified before it is collected, disposed of, or recovered. There is no WRAP protocol for soils, but characterisation, sampling and classification of soils arising from development sites has been incorporated within the Environment Agency’s Technical Guidance WM3.

Waste soils can be classified as either hazardous or non-hazardous based on review of ‘routine’ laboratory testing (which provides information on composition).

If soils are classed as Non-Hazardous, they can go to a Non-Hazardous landfill facility; no further testing (e.g. WAC) is required, although the landfill operator may still request it.

Regardless of the waste classification, if soil is destined for Inert, Hazardous or Stable Non-Reactive Hazardous landfill, then WAC testing is required and must be undertaken. WAC testing provides an indication of how the waste will behave once it’s buried in a landfill, including what will leach out of it.

Ideally, waste classification should be carried out on samples recovered from stockpiled material, following the necessary mass excavation associated with preparatory earthworks, rather than samples recovered during a site investigation. This is because the supervising Engineer is able to see a significant proportion of the soil\fill and surplus excavated soils can then be appropriately segregated and assessed (via the analysis of composite samples that are likely to be more representative of the material mass than discrete ‘spot’ samples).

However, it is appreciated that Developers usually need to know the likely proportions of hazardous and non-hazardous soils well in advance of a site start. This can be done, but it should be borne in mind that waste classification based on SI data is less robust and some contingency is prudent for ‘unexpected’ material which might subsequently be encountered during the preparatory earthworks.

Lithos can review laboratory results and consider these against the relevant hazardous properties and concentration limits within WM3. Our approach is to undertake waste classification on ground types as a whole, rather than classification based on individual samples.

We are able to undertake relatively simple, basic reviews to provide an indication of whether the surplus soil is hazardous or non-hazardous, and provide the likely waste code(s). However, in some cases, particularly where there is a mixture of contaminants, or individual metal concentrations are found to exceed 1,000 mg/kg, a more detailed assessment will be required.