Understanding the Importance of Land Contamination Assessment

Key Takeaways

• Land contamination assessments are essential for identifying hazardous substances and mitigating health and environmental risks, especially in historically industrial areas.

• Regulatory compliance is a key element in managing land affected by contamination and the associated liabilities, and requires appropriate assessments and remedial strategies that ensure safe developments and environmental protection.

• Successful remediation projects not only restore contaminated sites but can also enhance property values and contribute to the regeneration of local communities.
   

Understanding Land Contamination

Land contamination is caused by the presence of hazardous substances in soil and groundwater, and is typically the result of activities such as industrial operations, waste management / disposal and agriculture.
 

Hazardous substances can impact a site through various means, such as historical on-site uses, migration from neighbouring land and atmospheric deposition of pollutants, but can also originate from natural sources.

The legacy of the UK’s industrial past has left many brownfield sites in a state that could be statutorily determined as Contaminated Land under the UK contaminated land regime.
 

Brownfield land refers to previously developed sites, and are often prime for redevelopment due to their location and existing infrastructure. However, these sites may have contamination issues that need to be addressed through the planning regime in line with sustainable development policies such as the National Planning Policy Framework (NPPF).
 

Contamination can occur in a variety of forms, which includes chemical, biological, and radioactive substances. Former industrial sites like petrol stations, gas works, oil depots, and factories will often be chemically contaminated due to their past activities with a variety of substances.
 

Contaminants may have a range of behaviours. For example, some volatile organic compounds (VOCs) can readily vaporise or may be relatively short-lived in the environment due to natural biodegradation processes, while others such as PFAS (per- and polyfluoroalkyl substances) persist in the environment for a long time, presenting ongoing risks.
 

A site can be considered to be contaminated if contaminant levels have significant potential to adversely affect human health or the environment. Knowing the sources and types of contamination helps identify risks and plan suitable remediation efforts.
 

Health Risks Associated with Contaminated Land

Land affected by contamination can negatively impact human health, not only through direct exposure on affected sites, but indirectly through wider impacts that stretch beyond site boundaries.
 

Pollutants in contaminated soil can migrate via the water environment and through the air, and be taken up by plants and animals to enter into the food chain. Pollutants can enter groundwater through leaching from soils, which can impact the quality of drinking and irrigation water.
 

Site investigations identify the harmful substances in soil and groundwater that have the potential to impact human health and the environment in the context of a proposed development.
 

Environmental Impact of Land Contamination

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The environmental impact of land contamination can be significant, contributing to the loss of biodiversity and disruption of ecosystems. Pollution of soil can significantly reduce the diversity and activity of organisms living within it. When pollutant levels reach toxic thresholds, sensitive species may be entirely eliminated from the soil ecosystem.
 

Effective management of contamination during the redevelopment process can improve environmental conditions. Contaminants from polluted land may leach into groundwater, which can present unacceptable risks to human health and local ecosystems. 
 

Water bodies such as rivers and lakes are particularly vulnerable to contamination from runoff or groundwater, making their protection an important component of environmental assessments.
 

Addressing land contamination and implementing pollution prevention measures are essential steps in preserving the environment and demonstrating sustainable development.
 

Regulatory Requirements for Contaminated Land Assessments

In the UK, Part 2A of the Environmental Protection Act establishes the framework for assessing and managing contaminated land. The National Planning Policy Framework outlines requirements for land contamination assessments as part of the planning process.
 

Local authorities play a crucial role in enforcing these regulations and are responsible for the determination and management of contaminated land in their areas. The local planning authority is responsible for reviewing contaminated land assessments and ensuring that sites do not present an unacceptable risk based on their intended use before granting planning permission.
 

Local planning authorities utilise conditions to guide specific requirements for contaminated land assessments. A land contamination assessment may be required to discharge a planning condition imposed by the local planning authority.
 

Conducting contaminated land assessments is advisable before purchasing land to identify potential liabilities and the likely requirements to comply with local authority planning conditions.
 

The Environment Agency, Natural Resources Wales, and SEPA regulate special contaminated land sites (such as nuclear sites).

Other organisations, such as The National House Building Council (NHBC), set standards for new developments and may require contaminated land assessments as part of their building warranty processes.
 

Contaminated land assessments should be undertaken by experienced practitioners who hold relevant qualifications and accreditations that demonstrate technical expertise. Key standards and accreditations include:

• The National Quality Mark Scheme (NQMS), which ensures professionals meet legislative and quality standards in reporting.

• Suitably Qualified Person (SQP) designation.

• Specialist in Land Condition (SiLC) qualification.

• Relevant charterships, such as Chartered Geologist (CGeol) or Chartered Environmentalist (CEnv).

• SoBRA certification, which demonstrates expertise in land contamination.
   

The Role of Preliminary Risk Assessment

A Preliminary Risk Assessment or Phase 1 Desk Study is the first stage of land contamination assessment and involves:

• Gathering historical maps and current site information, and undertaking a site walkover survey.

• Identifying potential contamination sources and hazards.

• Assessing the risks and determining the scope for further investigations.
   

A site walkover survey is a visual inspection of the site to supplement the desk study findings and identify potential contamination sources.

Where possible, consulting site personnel during the site walkover can provide valuable information about historical and current site activities that may not be recorded elsewhere.
 

The desk study and site walkover survey are used to develop a Conceptual Site Model (CSM), which is a visual representation of the source-pathway-receptor pollutant linkages. Phase 1 assessments identify these potential contaminant linkages and the likelihood of them being significant, and form the basis of subsequent phases of investigation. This phased approach is essential to allow informed decisions about safe development.
 

Importance of Site Investigations​​

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Site investigations (Phase 2) provide the actual site data that is used to understand the ground conditions, such as soil type, groundwater level, potential ground gas sources and chemical characteristics, in order to assess site suitability and develop a remediation strategy.
 

During Phase 2 investigations, soil and water (groundwater and surface water) samples are collected from various locations (from boreholes and trial pits) and depths, and sent to a laboratory for analysis.
 

The detailed investigations are the basis of assessments that identify and quantify the potentially hazardous substances and help refine the conceptual site model. From these assessments, suitable mitigation measures are developed to enable the safe redevelopment of contaminated sites and ensure compliance with regulatory standards. Safe development rests on a robust investigation and a thorough interpretation of the results.
 

Detailed Quantitative Risk Assessment Explained

A Detailed Quantitative Risk Assessment (DQRA) is undertaken to determine acceptable contaminant concentrations in the context of the proposed or current development site use, and therefore whether remediation will be necessary or not.
 

The information collected during the Phase 2 investigation is input into an appropriate model, such as the Contaminated Land Exposure Assessment (CLEA), Remedial Targets Methodology or ConSim. The models are a mathematical simulation of the fate and transport mechanisms for the identified contaminants, and allow an estimate of the exposure of site users or other sensitive receptors. This allows the calculation of acceptable target concentrations that do not pose any unacceptable risks.
 

The DQRA will consider all foreseeable routes of exposure, such as direct contact, ingestion and inhalation of contaminated soil, as well as exposure to substances such as free-phase hydrocarbons or waste acid tars.
 

Mitigation and Remediation Strategies

Where unacceptable levels of contamination are identified at the risk assessment stage, remediation and / or mitigation measures will be required to ensure the site is suitable for use. It is essential to properly address contamination to prevent ongoing risks to human health and the wider environment.
 

There are a wide variety of techniques that can be used, ranging from very simple interventions to more technical approaches for the more challenging contamination scenarios. These techniques include:

• Simple cover layers: Hard surfaces or a surface layer of clean soil to manage exposure to low levels of contamination.

• Gas / vapour protection: Features such as gas resistant membranes and ventilation layers incorporated into new buildings to prevent the ingress of ground gases or vapours.

• Bioremediation: Utilises natural biological processes to degrade pollutants.

• Phytoremediation: Employs plants to absorb and remediate contaminants from soil and water.

• Soil washing: A treatment method that separates contaminated soil particles from clean ones using water-based techniques.

• Chemical oxidation: the injection of chemical agents into the ground to degrade contaminants.

• Permeable reactive barriers: installed in the ground to intercept and neutralise contaminants in groundwater.
   

Successful remediation projects have transformed former industrial sites into vibrant new developments, helped regenerate otherwise derelict areas and improved facilities for local communities.
 

Financial Implications of Land Contamination

Understanding the financial implications of land contamination is essential for property owners and those involved in property transactions. While there are costs associated with the investigation and remediation of contaminated land, these are often outweighed by the impact of potential liabilities on property values.
 

The presence or potential for land contamination, may affect property values in the following ways:

• Blight: the perception that potential contamination may affect the utility of a site.

• Potential liabilities in terms of unknown remediation costs and possible legal penalties for environmental damage

• The unsuitability of land for certain types of development
   

A detailed characterisation of the risks and the development of a cost-effective remediation strategy can eliminate uncertainties, address potential liabilities and increase land values.
 

Failing to fully address potential contamination can result in unexpected costs related to necessary remediation, delays and regulator interventions.
 

How Land Contamination Affects Planning Permission

The National Planning Policy Framework requires a contaminated land survey as part of the planning process. Developers must ensure any contamination risks are considered before submitting a planning application, and a Phase 1 desk study is often required to be submitted with planning applications to meet local authority requirements, with later stages of assessment dealt with through planning conditions.
 

Planning permission may be refused if insufficient information is submitted with the planning application. It usually must be demonstrated that a site is low risk, or that remediation works have been accounted for when considering the development viability.
 

Local Planning Authorities need to ensure a proposed development does not pose significant risks. The National Planning Policy Framework encourages the sustainable redevelopment of potentially contaminated sites, and emphasises the importance of thorough assessments and appropriate remediation.
 

Why Choose G&J for Your Contaminated Land Risk Assessments?