Contaminated land contains substances that are genuinely or potentially hazardous to health or the environment. A contaminated land assessment is used to evaluate the potential for a pollution linkage and consider whether actions are required to manage or mitigate the risk.
Contaminated land assessment is required as part of a planning application or to discharge planning conditions imposed by the local authority, Environment Agency or National House Building Council.
Contaminated land assessments are additionally used to investigate potential environmental liabilities or if a regulatory authority requires an assessment to investigate a potential or on-going pollution issue. (For example, if a site is being investigated under Part 2A of the Environmental Protection Act 1990.)
Regulatory bodies such the Environment Agency and the local planning authorities apply the ‘source-pathway-target’ pollutant linkage when assessing the risk to sensitive receptors. Land is declared contaminated if:
It contains significant levels of a pollutant (known as the ‘source’).
Someone or something (known as the ‘target’ or ‘receptor’) could be affected by the pollutant.
The pollutant can get to the receptor in significant quantities (known as the ‘pathway’).
Contaminated land assessment broadly follows a phased approach. The investigation and remediation process is typically split into four separate phases or stages:
Phase 1 – Desk study and site reconnaissance
A preliminary risk assessment is required to obtain a thorough understanding of the site history, setting and potential to be affected by contamination. The risk assessment comprises desk study research, site reconnaissance and the development of a conceptual site model.
Phase 2 – Intrusive investigation
If the desk study indicates there is a potential for contamination, an intrusive site investigation and refined risk assessment will be required. The purpose of the investigation is to determine whether there are any unacceptable risks to people, property or the environment.
Phase 3 – Remediation
If the intrusive investigation identifies any unacceptable risks, then remediation will be required. Remediation involves the clean-up of a site to ensure it is suitable for use. Remediation may include excavating the contamination or installing clean cover.
The remediation method statement will set out what action is required to make the site suitable for use and provides details on how such works will be carried out. The remediation proposals should be submitted to and approved by the local planning authority prior to the works being carried out.
Phase 4 – Verification
Verification (or validation) works are undertaken following remediation. The purpose is to confirm the success of the remediation works. The verification report will provide a descriptive record of the site remediation works and independent verification of the emplacement of imported topsoil in areas of soft landscaping.
The verification report will reference the prior reports and contain a summary of the risks that are being managed. All details of the remediation exercise, management documentation, and any variation in conditions encountered on site will be documented. The report will include details of work; approvals; waste transfer notes; all certificates; and correspondence with the local planning authority and other regulators.