Investigation and risk assessment before works commence on site

The assessment of land that is contaminated or where contamination is suspected is a complex process. Site investigation and sampling are part of this process and should only be undertaken by those organisations or individuals who are competent, experienced and insured to undertake this type of work.

The information gained by these investigations is very important for:

• safe design and implementation of site works
• the design of the development
• protection of humans and the environment
• identification of safe disposal routes for contaminated materials
• determining what environmental permits and authorisations will be required for the site works.

Commissioning a site investigation

If you are commissioning a site investigation for your construction site, make sure it is carried out in accordance with British Standards, best practice and current guidance.

It should include:

• A desk study including the collection and evaluation of historical information about previous site uses, the sorts of chemicals that could be present, their behaviour and their potential effects on the environment. The desk study is used to decide if further information is needed, and how it will be collected.
• The collection and testing of samples of soil and water using intrusive methods such as installing boreholes or excavating trial pits.

Intrusive site investigations need to be properly designed to collect the right quality and quantity of information.

Any site investigation must be undertaken in such a way that protects human health and the environment and should be carried out in accordance with:

• BS5930 - Code of practice for site investigation
• BS10175 - Code of practice for investigation of potential contaminated land sites.

Any report outlining the results should include a plan of the site showing where the samples were taken.

An accredited laboratory must undertake the analysis of samples taken from the site. Ensure that information on testing processes used and equipment calibration certificates are included in the results document.

Make sure that the laboratory tests run on the samples from the site include appropriate tests for all contaminants identified as likely to be present by the desk study (preliminary risk assessment).

Investigations for contamination can be undertaken separately or with other investigations, such as geotechnical works to collect information for foundation design.

An interpretative report should accompany the results. Specify what you want to use the information for. Use experienced contractors who can use the information that they have obtained to advise you.

Find information about the history of the site

Try to find out if a previous desk study and/or site investigation has been undertaken at the site. If so, try to get a copy of it. This information will need to be reviewed to see if it is suitable and relevant to the design of the proposed investigation. Previous site surveys may give you an indication of what should be included in a site investigation and may give an idea of what results to expect. This is an indication only. Do not rely on historic surveys undertaken by others.

If no information is available about the site, a good desk study and conceptual model are required prior to designing the site works.

Your local council Environmental Health Department or environmental regulator may hold information about the history of the site.

Northern Ireland: DAERA - Contaminated land

Scotland: SEPA contaminated land