What we do Soil resource, MMPs & waste

Soil resource & soil resource plans

Some local authorities now require a Soil Resource Survey and\or a Soil Resource Plan to be submitted in support of the planning application for development on a greenfield site.

A Soil Resource Survey essentially establishes the quality of topsoil and subsoil.

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

Lithos have several suitably qualified and experienced soil scientists and are able to undertake Soil Resource Surveys and draft Soil Resource Plans. An example of what we do can be found here in our Case Studies.

Soil is a fundamental and ultimately finite resource and some of the most significant impacts on this resource are associated with construction activities. However, it appears that there is a general lack of awareness and understanding within the construction industry of how to deal with soils in a sustainable way.

Defra issued a Code of Practice in 2009 providing guidance for the construction sector on how to better protect the soil resources with which they work. If this guidance is followed, developers will also likely achieve cost savings.

The Code recommends that developers commission a Soil Resource Survey prior to commencement of any earthworks in order to assess the quality, quantity and suitability of both topsoil and subsoil for the intended on-site uses.

The Survey usually comprises shallow hand-dug pits excavated by a suitably qualified and experienced soil scientist to allow description of each soil layer (colour, texture, drainage characteristics etc). A minimum of 10 locations should be investigated, with at least one pit per hectare on larger greenfield sites.

The Code states that ‘standard’ site investigation reports should not be relied on to provide detailed information on topsoil and subsoil resources. Consequently, a Soil Resource Survey should be commissioned separately to ‘standard’ site investigation, or at least as a specified, discrete additional requirement.

Information gathered during the soil resource survey should be used to prepare a Soil Resource Plan which can in turn form a sub-section of the Materials Management Plan for the project. Soil Resource Plans provide advice on the correct handling, storage, treatment and placement of topsoil and subsoil. Soil types, areas of soil to be stripped, haul routes and stockpile locations should be clearly defined within the Plan.

A Soil Resource Survey and Soil Resource Plan will provide the data necessary for determining whether development will require import of topsoil, or (more likely for wholly greenfield sites) result in surplus topsoil and\or subsoil. Only when required quantities topsoil and subsoil have been set-aside for use on site for landscaping, gardens, etc. should other uses (or export) be considered.

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 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 all scenarios, Lithos can produce a MMP, including completing the CL:AIRE MMP Form which requires answers to 26 questions, following review of the relevant documents (including Site Investigation & Remediation Strategy Reports).

For more complex brownfield sites, close liaison with the appointed Contractor is necessary as they will need to undertake some earthworks modelling, with reference to existing and proposed levels, in order to determine anticipated volumes of cut and fill. The appointed earthworks Contractor will also need to provide information regarding their proposed method of working; i.e. annotated drawings showing the different excavation areas, stockpile locations etc.

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.

The re-use of clean natural soil arisings on the site from which they have been excavated, where such re-use is a certainty, falls outside of the scope of the Waste Framework Directive and CoP. Consequently a MMP is not required. Preparation of a MMP in advance of earthworks / development could be useful to help the developer assess the cut/fill balance and any likely surplus or shortfall of soils. However, in this scenario the MMP would not need to follow the CoP format, require review by a QP or declaration to CL:AIRE.

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.