If you are about to buy, sell or refinance a property, or if you are applying for planning permission, you will need to know if your land is contaminated. The first stage of the process is to do a search on the site.

The site search must be completed during the due diligence process, which is typically carried out by a lawyer or conveyancing agent, who will check the details against a database. The search will list all registered uses of the site and neighboring areas (usually within 250m of the property).

Approximately 5% of all UK site searches reveal the property to be on or near land once used for industrial activities. If your site is on or near a former industrial site, you will need a contaminated soil assessment.

The staged approach to risk management used in the UK makes this a complex process. To guide you through the maze of regulations below, there is a simplified two-step process for understanding parts of the legislation surrounding contaminated land.

Step 1: Check with the Local Authority and the Environment Agency.

As legal regulators of contaminated land issues, the opinions of the Local Authority and the Environment Agency on the site are most important. They can determine if the property is acceptable or if further evaluation is required. If the local authority is not concerned about contamination on your land, then you do not need to take any further action.

If there are concerns with the site, the local authority will be able to guide you on what to do next. If the land is contaminated to the extent that it may be affecting ground or surface water, the Environment Agency should be contacted as they regulate the aquatic environment and will also provide guidance.

Step 2: Risk assessment

If regulators cannot rule out contamination issues, the next step is to conduct a risk assessment as required by the Environmental Protection Act of 1990. This step should be completed using a qualified contaminated land consultant or professional. The risk assessment process is divided into three phases.

In Phase 1, your consultant will interpret information obtained from site searches and other publicly available information, such as geological and hydrological maps. They will also conduct a site tour to gain an understanding of the area on the ground. From this information, they will develop a Conceptual Site Model (CSM) and complete a Qualitative Risk Assessment (QRA) in accordance with UK guidance. If the QRA demonstrates low risks, no action is required. If the QRA indicates medium or high risks, then a Phase 2 contamination assessment is required.

The Phase 2 evaluation involves physical sampling of the soil to confirm the level of contaminants. These results are compared to the UK soil and groundwater thresholds (Generic Assessment Criteria or GAC) to determine whether and to what extent the soil is contaminated and poses a risk. If the site is contaminated, remediation will be required. This is Phase 3.

Your consultant will agree to a Phase 3 remediation scheme with the Local Authority and will be able to monitor and report on the progress of the scheme. They can also manage the entire process on your behalf.

Guidance documents relevant to housing are DEFRA & Environment Agency (2004) Model of Procedures for the Management of Soil Contamination and NHBC and CEIH (2008) Guide for Safe Housing Development on Land Affected by Contamination.