Contaminated land contains substances that pose serious health and environmental risks. If there is reason to believe that contamination exists in a proposed site for development, a contaminated land assessment must be carried out. This type of testing identifies pollutant linkages and enables the local planning authority to assess whether remediation is necessary before proceeding with the project.
The assessment is divided into four distinct phases:
Phase 1 – Preliminary Site Survey
An initial site investigation must be undertaken to assess the proposed site’s history, setting, and suitability for residential, commercial, or industrial reuse. During the investigation, evidence of past contaminative activity is identified as well as actual and potential pollutant linkages.
A phase 1 land contamination assessment involves:
- Desk Study
- Site Walkover
- Conceptual Site Model
- Risk Assessment
- Conclusion to Assessment
A phase 1 survey determines the past uses not just of the targeted land but also nearby areas. This is crucial since contaminants often travel away from their source, polluting adjacent sites. The findings in this phase will help pinpoint potential pathways for bacteria and rule out the need for subsequent works at an early stage.
Phase 2 – Intrusive Investigation
If the historical and current data gathered during Phase 1 indicates a potential for contamination, a more detailed risk assessment will be required.
Phase 2 involves site characterisation through soil and water sampling. The purpose of this test is to determine whether professional environmental solutions are needed to make the target site suitable for the proposed land use.
The type of test to be carried out will depend on the extent of contamination. They can take the form of simple soil sampling to borehole drilling and groundwater and gas monitoring.
Phase 3 – Site Remediation
Remediation takes place when a site is declared contaminated and unsuitable for the suggested land use. During this phase, mitigation measures are provided to allow the development project to proceed.
The remediation method statement indicates which actions must be performed to achieve the appropriate site conditions. Remediation may include:
- Excavation of existing contamination
- Continuous on-site monitoring and treatment
- Installation of clean cover
- Thorough clean-up of the site
- Use of barrier membranes or capping
The proposed actions should be approved by the local planning authority first before carrying out any work.
Phase 4 – Verification
Site verification or validation confirms the success of the remedial works and that the site’s condition is now fitting for its proposed functions. In cases where a full clean-up is not possible or on-site containment of pollutants is done, continuous monitoring and maintenance is required.
The verification report will detail all the site remediation works that were carried out. It will also mention past reports and identify the risks that were mitigated and those that are still being monitored. Moreover, the report will document all local approvals, certifications, waste transfer notes, and correspondence with the local planning authority throughout the course of the site assessment.
No construction project can proceed without first ensuring that the land can support the proposed site use. Identifying and mitigating risks early on can lead to higher cost savings, smoother development process, and greater safety for all.