The term ‘brownfield’ describes previously developed land. It is defined as land that is or was occupied by a permanent structure (excluding agricultural or forestry buildings) and associated fixed surface infrastructure.
The establishment of greenspace on brownfield land can provide many social and environmental benefits, such as opportunities to walk and cycle, increased wildlife and flora, and reduction in noise and air pollution. It can also contribute to the economic regeneration of an area.
The establishment of woodland and associated greenspace should be in line with environmental good practice.
A greenspace development project is a four-step process.
- Identification and reclamation
- Site identification and shortlisting according to local availability, project goals and regional priorities.
- Evaluation of shortlisted sites according to soil conditions, likely impacts of vegetation establishment, liabilities and risks, and remediation of unacceptable risks.
- Consultation and design
- Consultation of statutory and non-statutory stakeholders and design of the master plan for implementation.
- Implementation and delivery
- Civil engineering of infrastructure (and possibly buildings).
- Provision of facilities and services (e.g. lighting).
- Ground preparation, planting and fencing.
- Management, monitoring and maintenance
- Ongoing processes of pest control, health and safety assessments, habitat care and community liaison.
To protect natural and cultural heritage and important features of the landscape, shortlisted sites are evaluated in detail using desktop studies and site surveys according to British standard codes of practice (including BS 5930 and 10175) and government guidelines such as the Environment Agency’s contaminated land reports.
Step 1. Identification and reclamation
Soil condition and impacts of vegetation establishment
The overall success and sustainability of a greenspace project are affected by:
- The abundance of soil, its fertility and potential to sustain vegetation
- The consequences of tree and plant growth, such as potential damage to pollution-control measures or cultural heritage.
The soil environment is a focal point of site investigations. It is important to continually address four questions throughout the site investigation process.
- Will the site support trees and vegetation? (In particular, its water-holding capacity; contamination, fertility and nutrient status; physical soil characteristics; soil cover and rootable depth; and topography.)
- Will the establishment of greenspace generate, amplify or negate risks and hazards?
- Will vegetation establishment adversely affect the site?
- How will the site be managed in the short and long term?
Many of the UK’s urban and peri-urban brownfield sites are potentially contaminated. Current UK planning guidelines specify that the redevelopment of land in England, Scotland and Wales must ensure ‘suitability for use’ – all risks at a site must be assessed and evaluated according to the intended use of the land.
Part IIA of the Environmental Protection Act 1990 requires all local authorities to inspect their area for contaminated land, and to secure its remediation to a condition that is suitable for current types of use. Assessment is also required to identify all risks present at a site and those that may arise following modification, alteration or management. Other legislation includes statutory nuisance, health and safety, waste and landfill legislation, planning and development control, and the Groundwater Regulations 1998.
A vital component of site evaluation is the assessment of risks and liabilities for each site:
- Identify potential risks and liabilities, including potential for contaminated land
- Review potential end-uses
- Assess potential for greenspace development
- Protect developers and future users
- Protect health of the environment
- Ensure reclamation does not increase current risks or create new risks.
A full evaluation is a must to identify which shortlisted sites can proceed with greenspace establishment. Contaminated land is defined as ‘any land which appears to be in such a condition, by reason of substances on, in 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’ (Part IIA of the EPA, 1990).
Dealing with contaminated land is about risk management. It is a process of ‘identifying, assessing and judging risks; taking actions to mitigate or anticipate them; monitoring, and reviewing progress’ (Environment Agency, 2004).
A simple example: a hazard may be a cracked paving slab. The risk is the probability (or likelihood) that someone will trip on the cracked slab and fracture a bone. Risk can be expressed numerically or literally. For example, one in every 10,000 people are likely to fall on the broken slab and break a bone (a 1 in 10,000 chance); or, there is a very low risk of a person falling on the broken slab and breaking a bone.
In the context of land contamination, there are three essential elements to risk.
- A source – a substance (contaminant) in, on or under the land that has the potential to cause harm, or to cause pollution of controlled waters. It may be a point, linear, localised or diffuse source.
- A pathway – a route or means by which a receptor can be exposed to, or affected by, a contaminant. It may be via groundwater, surface water or sediment; drains, air/dust or vapour; direct contact (ingestion or dermal); plant uptake; or the food chain.
- A receptor – something that could be adversely affected by a contaminant, such as people, an ecological system, property or water body. A comprehensive summary of potential receptors is required to evaluate the potential impact of contaminant sources.
Based on Defra Circular 01/2006 (PDF-526K). Pathways may apply to list I or list II sources and multiple receptors.
The linked combination of source–pathway–receptor is termed ‘pollutant linkage’. Each of these three elements must be present and linked to constitute a pollutant linkage and a viable risk. A site will be designated as contaminated land if the pollutant linkage is significant – if significant harm will, or is likely to, be caused to the receptor. The conditions considered to constitute significant harm to the various receptors protected under Part IIA are detailed in the harm tables of the Part IIA legislation guidance.
Example of a pollutant linkage
Risk management is the process of identifying and evaluating risks, and then taking and monitoring mitigating actions as required. Risk management is a phased process:
- Risk assessment:
- Hazard identification
- Hazard assessment
- Risk estimation
- Risk evaluation
- Risk reduction:
One or more of these phases may be necessary to determine which sites proceed to greenspace development, with decisions made on a site-by-site basis.
Risk assessment consists of:
- Preliminary site investigation (preliminary risk assessment) – identifies and assesses hazards to determine the potential for risk (e.g. pollutant linkages)
- Intrusive site investigation (quantitative risk assessment) – describes the risks in greater detail through sampling, analysis and interpretation.
The requirement for an intrusive site investigation depends on the findings (risks, liabilities and uncertainties) of the preliminary site investigation.
A main output of the preliminary site investigation is the conceptual site model. This is presented in at least two formats in the preliminary site investigation report (such as site plans, cross-sectional diagrams, network diagram or matrix). It is constructed from information collected during a desk study and a site walkover, and consolidates information into plausible pollutant linkages that need to be verified.
Conceptual models allow an informed risk assessment to be undertaken for each pollutant linkage, taking into account the potential severity of the risk and the likelihood of the risk occurring. An overall evaluation of the level of risks present at the site is obtained and ranked on a scale of very low risk (insignificant) through to very high (significant) risk. Care should be taken to ensure the information is comprehensive and up-to-date. For example, the site walkover should be used to confirm and update information provided by the desk study as well as to seek new information (e.g. number and location of water courses; possibility of an archaeological interest at the site requiring further specialist information; access and security issues).
It is imperative that the preliminary site investigation report gives recommendations for required next steps and lists all the uncertainties and limitations of the conceptual model.
Progression to intrusive site investigations will not always be needed. For example, if there are no potential pollutant linkages, no potential risks identified at the site and no uncertainties, there will be no requirement for further assessment or investigation. On the other hand, a site may have been shown to be less practical, less economically viable, or offering fewer public benefits than alternative sites on the shortlist, so the process would not continue.
The processes of risk management rationalises site hazards to offer phased, negotiable risk management based on priorities. Although the process is potentially long, costly and complex, some steps are not required for many brownfield sites being redeveloped as community greenspace. It is important to undertake each step and phase thoroughly to allow the identification of opportunities to exit the risk management process and proceed with reclamation and establishment in the knowledge that key decisions were correct, accountable and valid.
Next steps – consultation through to management
Any brownfield regeneration or greenspace establishment of woodland and associated greenspace must preserve and protect important features of the landscape, cultural and natural resource heritage, in accordance with best practice. The potential of a site for greenspace establishment must be assessed and revised regularly during site selection, investigation and remediation. In effect, a greenspace establishment feasibility study is conducted alongside the risk management process and considers aspects such as:
- Whether tree growth will adversely affect the site
- Types of habitat to be created at this site
- Species of trees and plants most appropriate for the site.
Step 2. Consultation and design
Following risk management and/or remediation to the satisfaction of the regulating authority (usually the local authority), site reclamation proceeds to step 2.
Design is an iterative process between experts (landscape architects, engineers and scientists), site owners/managers and public stakeholder groups, which leads to production of the master plan. A master plan reflects the project’s aims and stakeholders’ desires, such as public benefit (improved health and well-being, increased access, recreation and education), catalysing local regeneration, and promoting environmental improvement (landscape, aesthetics and biodiversity).
Adopted ownership and involvement by the local community in a greenspace establishment project is pivotal to its long-term success. Feelings of pride and ownership are manifested in respectful patterns of site use and community engagement in, for example, volunteering and education events held on the site. Consultation with key stakeholders, including local community groups, businesses and interest groups, enables desires for the site to be considered and discussed. Providing a site that is appealing helps to ensure it will be well used and well looked after.
Step 3. Implementation and delivery
Step 3 encompasses civil engineering of infrastructure through to provision of facilities and services, ground preparation, planting and fencing.
To encourage ownership, delivery must actively involve the local community and stakeholders at all stages. Limitations on the delivery programme are identified during the design phase, enabling bottlenecks to be timetabled appropriately. For example, habitats or species may require protection to minimise disturbance, or may cause works to cease completely at certain times of the year, such as in the breeding birds season. Restricted-access areas are useful in such cases.
Flora and fauna to consider may include:
- Trees with preservation orders
- Certain mammals (such as dormice and badgers)
- All breeding birds
- Many insects.
In all cases, a license from the appropriate statutory body must be obtained. Such requirements should be anticipated during step 2, consultation and design. Specific guidance can be obtained from Natural England, Defra and the local authority. If the site has any archaeological interest, the relevant statutory body (English Heritage, Cadw in Wales or Scottish Natural Heritage) should be contacted.
Step 4. Management, monitoring and maintenance
This includes the ongoing processes of pest control, health and safety assessments, habitat care and community liaison. Following regeneration, a new greenspace requires management in the:
- Short term (weed control, tree protection)
- Medium term (pest control)
- Long term (path maintenance, health and safety checks on trees and recreational facilities, silviculture).
Maintaining the site so that it is appealing and safe for communities to enjoy increases use and helps minimise antisocial behaviour. Management also includes stewardship to promote biodiversity and maintain habitats in their designed state. Management plans written according to the site priorities assist in these matters and help to resolve potentially conflicting uses, for example recreational use close to areas that are designed for wildlife. Community engagement and volunteering should be encouraged to promote site sustainability.
Forest Research has been establishing vegetation on brownfield sites for over 40 years, and uses this expertise along with ongoing research to provide consultancy and research services to the Forestry Commission and external clients for a wide range of habitats and vegetation types.
- Extensive experience of conducting soil surveys, including soil mapping for description of the chemical and physical constraints of a soil resource (e.g. nutrient levels and availability; soil depth). Accurate local information is a must for informed decision-making, planning and designing urban greenspace.
- Advice and recommendations on the design and implementation of site investigations.
- Research into techniques for sustainable establishment of urban greenspaces and associated habitats, including development of best practice. We welcome the opportunity to undertake such research as part of a research collaboration with interested parties.
Forest Research Best Practice Guidance
Hutchings, A, Sinnett, D. and Doick, K. (2006). Soil Sampling Derelict, Underused and Neglected Land prior to Greenspace Establishment (PDF-955K). Best Practice Guidance for Land Regeneration, BPG Note 1. Forest Research, Farnham.
Doick, K.J. and Hutchings, T.R. (2008). Greenspace Establishment on Brownfield Land: The Site Selection and Investigation Process (PDF-1050K). Forestry Commission Information Note 91. Forestry Commission, Scotland.
Environment Agency (2004). Model Procedures for the Management of Land Contamination (PDF-1900K). Contaminated Land Report 11. Environment Agency, UK.
- May refer to, for example, disease, death or reduced yield.
- Event or situation (including a contamination source) that has the potential to cause harm to targets of concerns (receptors).
- Organotin compounds are chemical compounds based on tin with hydrocarbon substituents.
- The combination of the probability (or frequency) of occurrence of a defined hazard and the magnitude of the consequences of the occurrence