Selection of remediation options
The key themes in remedy selection are illustrated in Figure 1.
Figure 1. General Principles for Remedy Selection
Most remediation work has been initiated for one or more of the following reasons:
· Remediation may be necessary for land posing significant risks to human health or other receptors in the environment such as groundwater or surface water. The remediation may be enforced or voluntary.
· Remediation may be required to facilitate redevelopment of formerly used land, which may take place for strictly commercial reasons, or because economic instruments have been put in place to support the regeneration of a particular area or region.
· Repairs to previous remediation work may be necessary where a past remediation project has failed, or a redevelopment has been carried out with out adequate risk assessment and management. These situations are often due to inadequate site investigation in the first instance.
· Remediation may also take place on a voluntary basis without any regulatory requirement to control liabilities as an investment to realise a gain in land value. Two specific commercial activities are important drivers for such remediation projects:
· Divestment of industrial sites where a potential purchaser requires environmental liabilities to be defined or removed prior to purchase, and
· Acquisition / take-over, where a site has to satisfy the environmental policy of a new controlling company.
What can be done for any particular contaminated land problem will also be constrained by a set of boundaries that are specific for the particular location in question. These can be grouped into two broad categories:
· boundaries that intrinsic properties of the site, for example: geological conditions, the nature of the contamination, the accessibility of the site, the services available on a site (electricity, water etc), its proximity to sensitive stakeholders and many others,
· boundaries that are a related to the management of the site, for example: its ownership, the interests of other stakeholders, the time and budget available for remediation work, the linkage of the remediation work to activities on site before, during or after remediation.
The goal of risk management is to support decisions on risk acceptability for specified land uses and to determine the actions to be taken. It is the process of making informed decisions on the acceptability of risks posed by contaminants at a site, either before or after treatment, and how any needed risk reduction can be achieved efficiently and cost effectively. In this way, the over riding needs for the protection of human health and the environment can be clearly identified and work prioritised accordingly. Remediation activities are therefore employed to reduce risks, as illustrated in Figure 2. Note: In many European countries risk based decision making is primarily used for historic contamination. Where contamination takes place after agreement of Pollution Prevention and Control (PPC) remediation to pre-contamination levels may be required.
Figure 2 Risk Management and Risk Reduction (Nathanail et al. 2002)
A suitable technique is one which meets the technical and environmental criteria for dealing with a particular remediation problem. The issues that affect the suitability of a remediation technology for a particular situation are as follows:
· Risk management application
· Treatable contaminants and materials
· Remedial approach
· Overall strategy
· Implementation of the approach
Determining suitability is likely to proceed in a stepwise fashion. As far as possible lower cost information should be used, and expensive investigations applied only where strictly necessary. Established performance information and process descriptions are likely to be used to gain a general view of suitability, to arrive at a shortlist of possible remedial approaches. However, it may be necessary to carry out lab scale or pilot scale treatability studies for complex treatment approaches, or where site specific effects are likely to have a large bearing in likely performance of a remediation system.
It is possible that a proposed solution may appear suitable, but is still not considered feasible, because of concerns about:
· Previous performance of the technology in dealing with a particular risk management problem;
· Availability of services (e.g. water, electricity) and facilities on a site;
· Ability to offer validated performance information from previous projects;
· Expertise of the purveyor;
· Ability to verify the effectiveness of the solution when it is applied;
· Confidence of stakeholders in the solution;
· Its duration;
· Its cost; and
· Its acceptability of the solution to stakeholders who may have expressed preferences for a favoured solution or have different perceptions and expertise.
The stakeholders at the core of the decision making process for site remediation are typically the site owner and/or polluter, whoever is being affected by pollution, the service provider and the regulator and planner. However, other stakeholders can also be influential such as:
· Site users, workers (possibly unions), visitors,
· Financial community (banks, founders, lenders, insurers),
· Site neighbours (tenants, dwellers, visitors, local councils),
· Campaigning organisations and local pressure groups,
· Other technical specialists and researchers.
Stakeholders will have their own perspective, priorities, concerns and ambitions regarding any particular site. The most appropriate remedial actions will offer a balance between meeting as many of their needs as possible, in particular risk management and achieving sustainable development, without unfairly disadvantaging any individual stakeholder. It is worth noting at this point that for some stakeholders, the end conditions of the site are likely to be significantly more important than the actual process used to arrive at that condition. Such actions are more likely to be selected where the decision-making process is open, balanced, and systematic. Given the range of stakeholder interests consultation can be a time consuming and expensive process, particularly if approaches are only made at a late stage in decision making.
The concept of sustainable
development gained international governmental recognition at the United
Nation’s Earth Summit conference in
At a strategic level, the
remediation of contaminated sites supports the goal of sustainable development
by helping to conserve land as a resource, preventing the spread of pollution
to air, soil and water, and reducing the pressure for development on
The aim of the assessment of costs and benefits is to consider the diverse range of impacts that may differ from one proposed solution to another such as the effect on human health, the environment, the land use, and issues of stakeholder concern and acceptability by assigning values to each impact in common units. Deciding which impacts to include or exclude from the assessment is likely to vary on a site-by-site basis. In many instances, it is difficult to assign a strictly monetary or quantitative value to many of the impacts. Hence, assessments can involve a combination of qualitative and quantitative methods. It is also useful to include a sensitivity analysis step, particularly where this encourages decision-makers to question their judgements and assumptions through the eyes of other stakeholders.
There is often no one “best” solution for a contaminated land problem. Risk management has a dominant role in decision making for managing contaminated land as it provides a rationale framework for evaluating problems and determining the availability of solutions. It is not, however, the only decision criterion. The drivers for a remediation project, the boundaries limiting what can be done on a site, the suitability / feasibility of available remediation options, the views of different stakeholders and the wider effects of the remediation work should all influence the choice of approach. An appraisal of costs versus benefits can be a useful approach to integrating this wide range considerations. However, it is important that this appraisal is wider in scope than a purely financial assessment as many of the wider costs and benefits cannot easily, or even accurately, assigned a pecuniary cost.
It is increasingly common now to see a holistic approach to contaminated land management with site investigation, risk assessment and risk management activities taking place in an iterative way. At the heart of any site management work must be the derivation of a site conceptual model (SCM) that integrates what is already known about a site, and identifies both what still needs to be discovered, and how that information should be used. The SCM sets out the critical pollutant linkages of concern for a particular land contamination problem. It crystallises understanding of what needs to be done to achieve risk management, and from this point appropriate remediation techniques for those risk management goals can be chosen. The SCM should be established at the earliest possible stage of information gathering for a site, and then gradually extended and adapted as more information becomes available and as subsequent remediation activities take place.
Good information is a pre-requisite for decision making. Environmental risks are the reason that remediation work is being considered, hence the importance of risk assessment as a decision making discipline and the site conceptual model for integrating the information available. Industry and government agencies in several countries are now promoting a more integrated and iterative approach where site investigation, risk assessment, namely selection and remediation overlap in a way that it synergistic.
For example, if there is clear evidence of serious sources of contamination, they can be removed rapidly while site appraisal is still continuing. As remedies are considered site investigation can be adapted to provide better information to optimise remediation planning. Decision making can use pollutant linkages as an underpinning discipline.
Selection of remedial approach is likely to proceed in a stepwise fashion, with general information being used to arrive at a short list, and then detailed desk studies, and possibly treatability studies, undertaken to support a final selection. The broad classes of decision making influences described in this outline have not been prioritised. In practice some criteria may be seen as more important than others, and weighted accordingly. However, this depends greatly on the regulatory, policy and economic context for the site being considered, so no general rules can be offered here. The ideal position is that all factors described here are considered in a balanced, holistic and transparent way, and that the decision making process is explicitly recorded so that decisions can be revisited if future circumstances require.
Extracted from: Nathanail, J. Bardos, P. &
Nathanail, P. (2002) Contaminated Land Management Ready
Reference. EPP Publications/ Land Quality Press. Available from: EPP