The most frequent requests for soil contamination investigations come as a result of a planning condition imposed by the local authority. Soil contamination investigations are also often undertaken prior to sale of land or change of lease. Contaminated land investigations are undertaken in accordance with BS10175:2013 – Investigation of Potentially Contaminated Sites – Code of Practice.
Phase 1 / Desk Study
Guidance for undertaking soil contamination investigations is provided by British Standard BS10175:2013. The first stage of a contamination investigation should always be a desk study (sometimes known as a Phase One or Desk Top Study). This will provide information on the history of the site allowing an understanding of what contaminants may have impacted the site and highlighting parts of the site at particular risk of contamination. The guidance used for producing conceptual site models and undertaking contamination risk assessments in the Environment Agency’s Contaminated Land Report 11 (CLR 11)- Model Procedures for the Management of Land Contamination. The desk study normally includes:
- Review of historical map data.
- Review of environmental database information including landfills, historical mining, trade registry information, pollution incident records and geological hazard data.
- Review of published geological maps and historical borehole records held by the BGS.
- Preliminary consultation with the local contaminated land officer.
- Production of a preliminary conceptual model.
- A detailed risk assessment based on the available information.
- Recommendations for intrusive investigation, if required.
Phase 2 / Intrusive Investigations
The Desk study is often followed by intrusive investigation. This involves inspection and sampling the soils using either trial pits or bore holes.
EMS can provide several different types of trial pit and borehole, depending on what is required at the site:
- Hand dug trial pits
- Machine excavated trial pits (from mini-digger up to large tracked excavators)
- Dynamic windowless sample boreholes
- Cable percussion boreholes
- Rotary boreholes
The drilling is undertaken by specialist sub-contractors under the close direction and supervision of an EMS Geo-Environmental Engineer. Where necessary monitoring standpipes are installed in the boreholes to allow subsequent groundwater or ground gas monitoring or sampling.
Soils are logged in accordance with British Standard BS5930:2015 by EMS’s trained and experienced Geo-Environmental Engineers. Samples from the trial pits or boreholes are sent to a UKAS and MCERTS accredited laboratory for contamination testing.
The findings of the investigation are then assessed by EMS’s consultants. Contamination assessment is site specific; with the acceptable levels of soil contaminants depending on factors such as the proposed end use of the site and the organic matter content of the soil. A ground investigation report is compiled including: a detailed account of the work undertaken; the soils encountered; and the chemical contamination status; along with recommendations as to whether remedial measures are required.
If remediation of contaminated soils is required EMS work with the Client to devise the most cost effective and practical solution and produce a remediation method statement. EMS can also assist with supervision and validation of the remedial works.