Land contamination

Conceptual model: A representation of the characteristics of the site in diagrammatic or written form that shows the possible relationships between contaminants, pathways and receptors.

Contaminant: A substance that is in, on or under the land and that has the potential to cause harm or to cause pollution of controlled waters.

Contaminant linkage: The relationship between a contaminant, pathway and receptor. This is also referred to as source-pathway-receptor linkage. This can be ‘significant’ if it forms the basis for concluding that a piece of land is Contaminated Land.

Contaminated Land:  Defined in s78A(2) of EPA 1990 as “any land which appears to the local authority in whose area it is situated to be in such a condition, by reason of substances in, on or under the land, that (a) significant harm is being caused or there is a significant possibility of such harm being caused, or; (b) pollution of controlled waters is being, or is likely to be caused”.

Controlled waters: Defined by Water Resources Act 1991, Part III, section 104¹, which includes all groundwater, inland water, estuaries and coastal water to three nautical miles from the shore.

Data quality: The extent to which data about a site and its setting provide a complete, relevant, reliable and clear account of likely or true conditions.

Definition of Waste: Code of Practice (DoW:CoP) is a process which enables the reuse of excavated materials on-site or their movement between sites, utilising a Materials Management Plan. This is a voluntary scheme facilitated by CL:AIRE²

Desk study (sometimes known as a Phase 1 report or PRA): Interpretation of historical, archival and current information to establish where previous activities were located, and where areas or zones that contain distinct and different types of contamination may be expected to occur, and to understand the environmental setting of the site in terms of pathways and receptors.

Detailed quantitative risk assessment (DQRA):  Assessment of risk carried out using detailed site-specific information to estimate risk or to develop site-specific assessment criteria.

Detailed site investigation (Sometimes known as a Phase 2): Main stage of intrusive site investigation, which involves the collection and analysis of soil, surface water, groundwater, soil gas and other media as a means of further informing the conceptual model and the risk assessment. This investigation may be undertaken in a single or a number of successive stages.

Environmental impact: The effect of remediation treatments on the quality of the environment during or following remediation.

Exploratory investigation: Preliminary intrusive investigation of a site, designed to facilitate hazard assessment and conducted prior to the detailed investigations required for risk estimation.

Ex situ: Where contaminated material is removed from the ground prior to above-ground treatment or encapsulation and/or disposal on or off-site.

Generic Assessment Criteria (GAC): Criteria derived using general assumptions about the characteristics and behaviour of sources, pathways and receptors. These assumptions will be protective in a range of defined conditions.

Generic Quantitative Risk Assessment (GQRA): Risk assessment carried out using generic assumptions to estimate risk or to develop generic assessment criteria.

Geo-environmental investigation: the collection and analysis of surface water, groundwater, soil gas and other media as a means of further informing the conceptual model and the risk assessment to ascertain the suitability of sites for construction operations and civil engineering works.

Geotechnical investigation: the collection and analysis of physical (and limited chemical) properties of soil to ascertain the suitability of sites for construction operations and civil engineering works.

Gas Protection Verification Accreditation Scheme (GPVS): is a scheme that seeks to raise standards in membrane inspection, verification and reporting and provide all stakeholders involved in land contamination management with confidence that risks associated with ground gases have been adequately managed.

Ground Gas Risk Assessment (GGRA): Land contamination can give rise to ground gases which can pose a risk of harm to human health and / or property.  GGRA measures and monitors gases and analyses findings in order to assess the risk posed.

Groundwater: Under Part 2A, whilst the term “controlled waters” in relation to England has the same meaning as in Part 3 of the Water Resources Act 1991,  except that “ground waters” does not include waters contained in underground strata but above the saturation zone. The Environmental Permitting (England and Wales) Regulations 2016, schedule 22³.

Harm: Adverse effects on the health of living organisms or other interference with the ecological systems of which they form a part.

Hazard: A property or situation that in particular circumstances could lead to harm or pollution.

Health criteria value: Benchmark criteria that represent an assessment of levels of exposure that pose a risk to human health. For example, tolerable daily intake (TDI) and index dose.

Implementation plan: A plan that sets out all aspects of design, preparation, implementation, verification, long-term maintenance and monitoring of the remediation.

In situ: Where contaminated material is treated without prior excavation (of solids) or abstraction (of liquids) from the ground.

Management objectives: Site specific objectives defined by stakeholders that relate to regulatory, financial and commercial matters and the desired outcome of remediation.

MCERTS: The Monitoring Certification Scheme is a quality assurance scheme for providers of monitoring services, equipment and systems, which is administered by the Environment Agency and accredited by UKAS.

Materials Management Plan (MMP): See Definition of Waste: Code of Practice (DoW:CoP) above.

Monitoring: A continuous or regular period check to determine the ongoing nature and performance of remediation, which includes measurements undertaken for compliance purposes and those undertaken to assess performance.

Non-aqueous phase Liquids (NAPLs): Liquids that do not mix readily with water.

Part 2A regime: Part 2A of the Environmental Protection Act 1990 is primary legislation which was introduced to provide a better way of identifying and remediating contaminated land.

Pathway: A route or means by which a receptor could be exposed to or affected by a contaminant.

Permeability: A measure of the ability of a medium to allow a fluid (gas or liquid) to pass through it.

Preliminary risk assessment (PRA): First tier of risk assessment that develops the initial conceptual model of the site and establishes whether there are any potentially unacceptable risks.

Receptor: In general terms, something that could be adversely affected by a contaminant, such as people, an ecological system, property or a water body.

Remediation: Action taken to prevent, minimise, or remedy or mitigate the effects of any identified unacceptable risks.

Remediation strategy: A plan that involves one or more remediation options to reduce or control the risks from all the relevant pollutant linkages associated with the site.

Response zone: The perforated section of standpipe which allows gas in the unsaturated zone or groundwater below the water table to enter a standpipe.

Risk: A combination of the probability, or frequency of occurrence, of a defined hazard and the magnitude of the consequences of the occurrence.

Risk assessment: The formal process of identifying, assessing and evaluating the health and environmental risks that may be associated with a hazard.

Risk management:  The process involved in identifying, assessing and determining risks, and the implementation of actions to mitigate the consequences or probabilities of occurrence.

Site characterisation: The process of gathering information about a site (or group of sites) and its setting(s) for the purpose of assessing and, where necessary, managing health and environmental risks.

Site-specific assessment criteria: Values for concentrations of contaminants that have been derived using detailed site-specific information on the characteristics and behaviour of contaminants, pathways and receptors and that correspond to relevant criteria in relation to harm or pollution for deciding whether there is an unacceptable risk.

Source: A hazardous substance or agent (for example a contaminant) which is capable of causing harm.

Special sites: Contaminated land for which the Environment Agency, rather than the local authority, becomes the enforcing authority. These categories of land are set out in the Contaminated Land (England) Regulations 2006 with similar provisions in Wales.

Supplementary investigation: Additional investigation carried out after a detailed investigation for the purpose of refining risk estimate and / or to assist in the selection of an appropriate remedial strategy, or for detailed (remedial) design purposes.

Uncertainty: A lack of knowledge about specific factors in a risk or exposure assessment including parameter uncertainty, model uncertainty and scenario uncertainty.

Unexploded ordnance (UXO): UXO is explosive ordnance that has been either primed, fused, armed or prepared for use and has been subsequently fired, dropped, launched, projected or placed in such a manner as to present a hazard to operations, persons or objects and remains unexploded either by malfunction or design.

Validation: The process by which a sample, treatment method, or data are deemed to be suitable for a specified process. Validation can be based on theoretical understanding of a process, a literature review of previous use, or determined on-site.

Vapour Risk Assessment: Land affected by contamination can give risk to volatile contaminants that can present a risk to human health and / or property. A vapour risk assessment will monitor and analyse vapours to assess the risks.

Verification: The process of demonstrating that the risk has been reduced to meet remediation criteria and objectives based on a quantitative assessment of remediation performance.

Verification report: Provides a complete record of all remediation activities on site and the data collected as identified in the verification plan to support compliance with agreed remediation objectives and criteria.

1. https://www.legislation.gov.uk/ukpga/1991/57/section/104
2. https://www.claire.co.uk/projects-and-initiatives/dow-cop
3. https://www.legislation.gov.uk/uksi/2016/1154/schedule/22/made