See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/228885198 General principles for remedial approach selection Article in Land Contamination & Reclamation · July 2002 DOI: 10.2462/09670513.614 CITATIONS READS 16 1,539 3 authors, including: Paul Bardos Judith Nathanail r3 environmental technology ltd Land Qualtiy Management Ltd 134 PUBLICATIONS 839 CITATIONS 15 PUBLICATIONS 54 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Colombia Prosperity Fund project on “Strategies for rehabilitating mercury-contaminated mining lands for renewable energy and other self-sustaining re-use strategies View project All Paul's current and past projects with r3 View project All content following this page was uploaded by Paul Bardos on 23 May 2014. The user has requested enhancement of the downloaded file. Land Contamination & Reclamation, 10 (3), 2002 © 2002 EPP Publications DOI 10.2462/09670513.614 General principles for remedial approach selection Paul Bardos, Judith Nathanail and Brian Pope Abstract Key factors in decision making for land remediation include: the driving forces for a remediation project, risk management, sustainable development, stakeholder satisfaction, cost effectiveness, and technical feasibility/suitability. These principles have been applied to an illustrative case study, a response to petroleum hydrocarbon contamination at a warehousing and distribution centre. The case study is fictitious, but based on several contemporary sites the authors have knowledge of. Key words: contaminated land remediation, remedy selection, risk management, sustainable development, treatment technology selection INTRODUCTION There are a number of factors that need to be considered in selecting an effective remediation solution to a contaminated land problem. These include the reasons for the remediation work and any constraints on it, risk management effectiveness, technical suitability and feasibility, stakeholders’ views, cost/benefit ratio and wider environmental, social and economic impacts (i.e. sustainable development). These key factors in decision making are illustrated in Figure 1. In addition, it is important to consider the manner in which a decision is reached. This should be a balanced and systematic process founded on the principles of transparency and inclusive decision making. This paper is written in four sections, and is based on the work of CLARINET – the Contaminated Land Received June 2002; accepted August 2002 Authors Paul Bardos, r3 Environmental Technology Limited, PO Box 58, Ware SG12 0AA. [email protected]. www.r3environmental.com. Corresponding author Judith Nathanail, Land Quality Management Limited, School of Chemical, Environmental and Mining Engineering, University of Nottingham, Nottingham NG7 2RD. [email protected], www.lqm.co.uk Brian Pope, Arcadis Geraghty & Miller International, Inc., Conqueror House, Vision Park, Histon, Cambridge CB4 9ZR. [email protected], www.arcadisgmi.com This is the first of three papers related to the work of CLARINET that will be published in this journal. Rehabilitation Network For Environmental Technologies in Europe (CLARINET 2002), a fictitious case study that is based on the site experiences of several consultants and remedial treatment information abstracted from Nathanail et al. 2002. The first section overviews these six theoretical decision making principles. The second presents a case study site and the third applies these principles to the case study site. The final section discusses the application of six theoretical principles in a practical context. The paper is not intended to provide a comprehensive application for each principle, but rather to show the application of a general framework for technique selection to a practical example. Towards the end of the paper, the reader is referred to sources of detailed guidance for that particular principle. GENERAL FRAMEWORK FOR TECHNIQUE SELECTION Driving forces and goals for the remediation project Most remediation work has been initiated for one or more of the following reasons: • To protect human health and the environment. Remediation of land posing significant risks to human health or other receptors in the environment such as groundwater or surface water. It may be required or voluntary. In both cases remedial objectives are set on the same basis: risk management. The contamination could either be from ‘historic’ contamination or recent contamination from an 137 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Figure 1. General principles for remedy selection industrial process or during transport. In some cases the remediation targets may be set to a more stringent threshold than one based on risk assessment. For example, the fuel oxygenate methyl tertiary butyl ether (MTBE) has a very low taste and odour threshold; remediation targets are likely to reflect this rather than risk based targets based on toxicity. • To enable redevelopment. Remediation of formerly used land 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. Remedial objectives are set on the (same) risk management basis, requiring consideration of all possible pollutant linkages; and also to achieve whatever site/ground improvements are necessary as a precursor to redevelopment. • To repair previous remediation work or redevelopment projects. Where a past remediation project has failed, or a redevelopment has been carried out without adequate risk assessment/management, further risk management actions may be necessary. Both situations are often due to inadequate site investigation in the first instance. • To limit potential liabilities. 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. Remedial objectives are set on the risk management basis, requiring consideration of all possible pollutant linkages; and also to achieve whatever site/ground improvements are felt necessary to improve asset values (if appropriate). Two specific commercial activities are important drivers for 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 138 the environmental policy of a new controlling company. Risk management A hazard is a substance or situation, such as contamination in the ground, that has the potential to cause harm (e.g. adverse health effects, groundwater rendered unfit for use, damage to underground structures, etc.) to a particular receptor. Risk is commonly defined as the probability that such a substance or situation will produce harm under specified conditions. Risk is a combination of two factors, the probability of exposure and the consequence of exposure. In the context of contaminated land management, risk occurs when three components are present (a source, a receptor and a pathway for that receptor to be exposed to the toxic substances from the source). Risks to human health (and other receptors such as groundwater) that may be caused by contamination are becoming a primary basis for supporting decisions on remediation throughout the EU and the USA (US EPA 1989; US EPA 1996a; US EPA 1996b; CLARINET and NICOLE 1998; Ferguson et al. 1998; Ferguson and Kasamas 1999). In this process of risk management, risk assessment is used to provide an objective, scientific evaluation of the likelihood of unacceptable impacts to human health and the environment. 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 necessary risk reduction can be achieved efficiently and cost effectively (Ferguson et al. 1998; Ferguson and Kasamas 1999). In this way, the overriding needs for the protection of human health and the environment can be clearly identified and work pri- General principles for remedial approach selection Risk Reduction: breaking the pollutant linkage by ….. Source Receptor Pathway …. source reduction ….. pathway management Reducing, removing, modifying, or destroying the contaminant sources, (e.g. in situ bioremediation of petrol contaminated soil) Preventing the further movement of hazardous substances en route to receptors, either by removing or destroying the contaminants or by preventing the transport pathway operating (e.g. by pump and treat or use of a physical barrier) …. modifying the exposure to the receptor Protecting the receptor (e.g. installing an alternative water source, preventing site access, or restricting land-use). Figure 2. Risk management and risk reduction (Nathanail et al. 2002) oritised accordingly.1 Remediation activities are therefore employed to reduce risks, as illustrated in Figure 2. Technical suitability and feasibility 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 and are outlined further in Table 1: • • • • • • • risk management application; treatable contaminants and materials; remedial approach; location; overall strategy; implementation of the approach; legacy. However, 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; 1. 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. • 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 • acceptability of the solution to stakeholders who may have expressed preferences for a favoured solution or have different perceptions and expertise. Stakeholder satisfaction 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 (SNIFFER 1999), such as: • site users, workers (possibly unions), visitors; • financial community (banks, founders, lenders, insurers); • site neighbours (tenants, dwellers, visitors, local councils); • campaigning organizations and local pressure groups; • other technical specialists and researchers. Stakeholders will have their own perspectives, 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 disad139 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Table 1. Factors affecting the suitability of a particular remediation technology (adapted from Nathanail et al. 2002) Risk management application Source control remedial action either to remove, or modify the source of contamination Pathway control remediation to reduce the ability of a given contaminant source to pose a threat to receptors by inhibiting or controlling the pathway by modifying its characteristics (Receptor control) Treatable contaminants and materials Contaminant(s) Concentration range Phase distribution Source and age Bulk characteristics Geochemical, geological and microbiological limitations Remedial approach Type of remediation system (containment, treatment: biological, chemical, etc.) each of which has its own particular strengths and weaknesses, for example based on space requirements Location Where the action takes place (e.g. in situ or ex situ, on site or off site) Overall strategy For example: • • • • • Implementation Linking remediation works/planning and further tiers of site investigation and risk assessment Integrated/combined approaches Active versus passive measures Long-term/low input (‘extensive’) versus short-term/high input (‘intensive’) Use of institutional measures (such as planning controls combined with long-term treatments) Implementation encompasses the processes of applying a remedial approach to a particular site and involves: • Planning remedial operations • Regulatory acceptance and licensing of a remediation plan1 – typically covering (in the UK) abstraction and discharge consents and Waste Management Licensing • Site management • Verification of performance • Monitoring process performance and environmental effects • Public acceptability and neighbourhood relationships (risk communication and risk perception) • Strategies for adaptation in response to changed or unexpected circumstances, i.e. flexibility • Aftercare • These activities are significantly different for different choices of remediation technique and are likely to be a significant cost element for a remediation project Legacy Destruction may be result of a complete biological and/or physico-chemical degradation of compounds, for example at elevated temperatures by thermal treatments.2 Extraction of contaminants may be brought about by (a) excavation and removal, (b) some process of mobilization and recapture, or (c) some process of concentration and recovery. Recycling might be the ‘ultimate’ form of removal. Stabilization describes where a contaminant remains in situ but is rendered less mobile and/or less toxic by some combination of biological, chemical or physical processes. 1. Typically, and perhaps unfairly, using conventional techniques does not generally run up against regulatory problems. Most discussion/negotiation centres around the risk assessment and extent of remediation/validation monitoring necessary. 2. Destruction may be incomplete, emissions and wastes are an outcome of all approaches, hence consideration of the fate of a compound should be considered during risk management and selection of remedial approach. vantaging 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, agreement of project objectives and project constraints such as use of time, money and space, can be a time consuming and expensive process. Seeking consensus between different stakeholders in a decision making process is an important factor in helping to achieve sustainable development. It is generally beneficial to involve all stakeholders believed to have a view early in the decision making 140 process. It is almost always counter-productive to present a solution as a fait accompli to a previously unconsulted stakeholder. However, stakeholder involvement is not without problems. There are several examples where decisions that were acceptable from a technical and regulatory perspective were not acceptable to all of the stakeholders; for example, siting of new waste disposal facilities and the use of the incineration as a treatment option have been prevented because of stakeholder concerns. The challenges are (Bardos et al. 2002): • the large number of stakeholders who might need to be involved; General principles for remedial approach selection • how to best express the ‘technical’ point of view in a process that is often to a large extent political, economic and social; and • how to ‘support’ the technical specialists so they can recognize the social and political dimensions of their efforts and identify stakeholders to be involved at an early enough stage – and facilitate the necessary communication. boundaries to what is feasible and realisable, for example relating to available time, space or money, as well as the nature of the contamination and ground conditions and what the site is, or is planned to be, used for. This compromise is reached by a decision making process involving several stakeholders (see below). This decision making process is often protracted and costly. The objectives set can be said to represent the core of the remediation project. Remediation processes are then commissioned to achieve these core objectives. Good practice is for a number of remedial alternatives to be selected and compared, which have the potential to meet the core objectives. However, the core objectives typically do not consider the overall environmental, economic and social effects of the remediation work to be carried out, i.e. they do not address its overall value in the context of sustainable development. For example, the overall environmental value of a project will be a combination of both the improvements desired by the core objectives, and also wider environmental benefits and impacts of the remediation work. Table 2 lists a series of wider environmental effects which are not necessarily considered to be at the core of a contaminated land decision. Consequently, it makes sense to choose a remediation approach that has the smallest negative wider environmental effect to reach the core objectives of the project. These wider effects are not considered by the core objectives, and so can be described as ‘non-core’. In Figure 3, the remediation ‘option 3’ has the best Sustainable development The concept of sustainable development gained international governmental recognition at the United Nations Earth Summit conference in Rio de Janeiro in 1992. Sustainable development has been defined as: ‘... development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ (Brundtland 1987). Underpinning this approach are three basic elements: economic growth, environmental protection and social progress. 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 greenfield sites. However, remediation activities themselves have their own environmental, social and economic impacts. Clearly, the negative impacts of remediation should not exceed the benefits of the project. The objectives that can be realized by remediation works represent a compromise between desired environmental quality objectives and project-specific Table 2. Some examples of the wider environmental effects of remediation activities Negative Positive • • • • • • • • Restoration of landscape ‘value’ • Restoration of ecological functions • Improvement of soil fertility (e.g. for some biological remediation techniques) • Recycling of materials Traffic Emissions (e.g. volatile organic compounds) Noise Dust Loss of soil function Use of material resources (e.g. aggregates) and energy Use of landfill resources Table 3. Examples of wider economic and social issues Economic consequences Social consequences • • • • • • • • Impacts on local business and inward investment Impacts on local employment Occupancy of the site Loss of revenue, for example to a site owner, through ongoing contamination/remediation operations • Compensation for or mitigation of effects of contaminants before and during remediation, and of any residual contamination left behind Removal of blight Community concerns about remedial approach Amenity value of the site Provision of infrastructure1 1. For example, in the UK a developer may offer the provision of infrastructure as a consideration in its planning and development negotiations with a local authority. 141 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 overall environmental ‘value’. Clearly, making this choice will depend on the affordability of the different remediation options available, set against the perceived value of the core objectives of the project and these wider benefits. Cost benefit analysis provides one means of making this assessment. A similar analysis can be made for the overall value in the contexts of social progress and economic growth (for examples see Table 3). Hence the overall value in the context of sustainable development is the combination of these overall environmental, social and economic values. This discussion paints a picture of risk assessment, practical constraints and available resources largely setting the boundaries for the main or core objectives of a remediation project, which are negotiated by a relatively small set of stakeholders. For remediation projects dealing with discrete sites, consideration of wider environmental or other effects is not obligatory and, at present, often does not take place. Where they are considered, it is usually after the core goals of a remediation project have been decided. Their consideration is then typically a part of the selection of an optimal, or ‘least worst’ remedial solution to achieve these core objectives. The objectives themselves are not questioned in this sequential approach. The increasing use of sustainable development indicators in corporate, environmental and planning environmental policy seems likely to lead to an increasing importance being attached to the wider environmental, economic and social affects of remediation projects over the coming decade, even for individual commercial projects. For larger remediation projects, in particular for areas of land where future reuse is not likely to be built development, or for aquifers which cross many property boundaries, a wider range of considerations will be made in the ‘core’ decision making process. This largely reflects the funding of such projects, which is often public funding, and the need to demonstrate that the work is a real permanent benefit to society (Environment Agency 2000a; Bardos et al. 2001). Costs and benefits 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. A range of guidance on cost benefit analysis has been published by the Environment Agency, which explicitly includes many of the wider sustainability and stakeholder involvement issues discussed above (see Table 11). THE CASE STUDY SITE The site is a warehousing and distribution centre for a transportation company. Elevated total petroleum hydrocarbons have been identified in soil. A layer of light non-aqueous phase liquid (LNAPL) is present locally. Dissolved phase hydrocarbons are present in Figure 3. The overall environmental value of a remediation project is the sum of environmental outcomes of the core objectives and its non-core effects 142 General principles for remedial approach selection Geology Pathways Fill (may be absent, discontinuous or continuous P1 Downward migration of contaminan via fill and sand and gravel Sand and gravel P2 Via groundwater London clay P3 Via vadose zone Water table P4 Direct exposure (dermal/ ingestion/ inhalation) Sources Diesel contaminated soil and groundwater Receptors Localised LNAPL Residents/ site operatives Sand and gravel Sand and gravel aquifer Figure 4. Site conceptual model 143 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Table 4. The case study site – overview of key site investigation information Site description The site is a warehousing and distribution centre for a transportation company. Much of the site is covered with hardstanding. Two above ground tanks exists on site for diesel. According the historical Ordnance Survey maps there appear to be no other contaminative uses on or near the site. It is intended that the current operations on the site will continue for five years. The site adjoins a residential area, and is half a mile east of the town centre and the local river. The site is at the edge of the gravel terrace on which the town centre is built, with chalk hills rising to the west. Geology and hydrogeology The northern two thirds of the site is underlain by Sand and Gravel of Quaternary Age. The rest of the site is underlain by London Clay, which also underlies the Sand and Gravel. The Sand and Gravel is classified as a Minor Aquifer. The London Clay is classified as non-aquifer. Site investigation carried out Following a desk study, 30 soil samples were tested for the ICRCL chemical suite and 20 samples were tested for total petroleum hydrocarbons (TPH) and polyaromatic hydrocarbons (PAH). 18 groundwater samples (3 from each of the 6 wells at 2 weekly intervals) were tested for the same set of determinands as the soil. See below Materials encountered A discontinuous layer of fill (0–0.8 m thick), followed by Sand and Gravel (northern two-thirds of the site only; up to 4m thick) over London Clay. Groundwater conditions encountered Groundwater was encountered at depths 1.8 m and 2.5 m below ground level (bgl) within the Sand and Gravel. Groundwater flow is to the north. Soil contamination 22 of the 30 samples tested for TPH detected TPH above the method detection limit. Concentrations ranged between 600 mg/ kg and 2000 mg/kg. This was predominantly the C10 to C12 carbon fraction which is the typical range for diesel. None of the six samples tested had PAH or metal concentrations greater than the ICRCL trigger values for buildings and hard cover (or parks, playing fields and open spaces where no trigger concentrations for buildings and hard cover are included in the ICRCL guidance). Groundwater contamination With the exception of TPH, the samples tested did not have concentrations of PAHs or metals above the UK drinking water quality standards (DWQS). Five of the six groundwater samples tested had a TPH concentration above 10 µg/L which is the DWQS for dissolved or emulsified hydrocarbons. The maximum concentration was 30 µg/L. (C10 to C12 carbon fraction) A layer of LNAPL is present in two of the monitoring wells; these were located close to the former buried tanks towards the northern end of the site. The LNAPL layer was measured as 20 mm thick although this may be an overestimate due to the way LNAPLs tend to accumulated in boreholes and depress the water table. Sources • Elevated concentrations of diesel in soils and groundwater (free phase product found to be diesel, with some signs of weathering) • A layer of LNAPL present locally • All located in vicinity of fuelling area on northern part of the site Potential pathway Fill and sand and gravel • Downward migration of contaminants to underlying sand and gravel which is a Minor Aquifer • Can also act as a pathway to adjacent sites Potential pathway Groundwater • A pathway to adjacent sites Potential pathway Vadose zone to adjacent garden • Hardstanding channels vapour to adjacent garden • Odour known to be present in at least one garden Potential pathway Direct exposure (Ingestion/dermal/possibly inhalation) • Elevated concentrations of TPH in soils • Site users may ingest soil • As most of the site is covered with buildings and hardstanding, this would only be an issue when parts of the site are excavated e.g. for service maintenance, extending buildings, site remediation • Potential volatilisation from groundwater to indoor air Potential receptors Human receptors • Residents • Site operatives during groundworks • Current/future users of the site Groundwater • Sand and gravel Limitations and uncertainties • Location of buried tanks • Whether TPH has migrated into soil beneath residents’ gardens • Whether TPH as LNAPL or dissolved phase has migrated off site • Whether vapours are migrating in other directions and may cause future nuisance 144 General principles for remedial approach selection the groundwater. The following receptors have been identified: groundwater, residents, site operatives. There are pathways present to all of these receptors. Table 4 provides a site outline, using the format suggested by Nathanail et al. 2002. The site conceptual model is illustrated in Figure 4. The case study is fictitious, but based on several contemporary sites the authors have knowledge of. APPLYING THE THEORETICAL DECISION MAKING PRINCIPLES TO THE CASE STUDY SITE Project drivers (driving forces and goals for the remediation project) The site owner was concerned to limit potential environmental liabilities following complaints and an approach from the local authority, it decided on a voluntary programme of site investigation and risk management if necessary. The complaints had been made by neighbours who had noticed a ‘funny smell’ in their houses, which in some cases was quite a strong odour. They had contacted their local authority, whose environmental health officer (EHO) had then approached the general manager for the site. Coincidentally, the company’s head office has just announced a rolling programme of strategic review of environmental issues. This programme encompassed an evaluation of land management issues, however, as yet no programme of site evaluation and prioritization had taken place. The company decided on a site investigation and if necessary remediation as a voluntary action ahead of the strategic review for several reasons: • because of the direct contact of the EHO; • long-standing neighbour issues around the site with objections to the timing of lorry movements; • as a case study to inform the strategic review of the company’s other sites. Unfortunately for the company, but not unexpectedly, the neighbour most affected by the odour was also the chief complainant about early morning and weekend lorry movements. The site investigation work found a significant source term, which appeared to be an accumulation of spills. Surface spills were evidenced by staining of the hardstanding, although their size was not immediately clear. Cracks were noted in the hardstanding, coincident with surface staining on several occasions. Damage was also found in the drainage to the hardstanding. Diesel was stored on site in above ground tanks, no evidence of major leakage from these was apparent. However, inspection of services indicated several minor leaks in fuel lines. It was concluded that the contamination found had accumulated over time from this leakage and from poor management of fuelling operations and low maintenance of the hardstanding. A small amount of localized LNAPL free product was found as a floating layer close to the site boundary, along with a more widespread dissolved phase spreading off site beneath. A substantial sorbed phase was also found in the vadose zone around the LNAPL free product. The project drivers was therefore seen as an emergency response, albeit a voluntary action, to protect human health and the environment. Three sets of actions were deemed necessary; • control of the source term; • amelioration of odours in the affected adjacent garden; • dealing with long-term liabilities presented by dissolved phase. A series of site specific factors or boundaries control how these actions can be carried out. Three critical boundaries are time, space and cost. • Time constraints. Time constraints on the project are not subject to the same pressure as for a redevelopment site. However, the company was anxious to remove odour as a cause for complaint from its site’s neighbour as quickly as possible. It was also keen that the dissolved phase should be remediated within five years, given the possibility of divestment of this site in the longer term. Hence, the site owner’s desired remedial response had to achieve source control and odour amelioration as quickly as possible, and dissolved phase remediation within five years. However, the regulator’s position was that they wanted to see a more rapid remediation of the dissolved phase, given the proximity of the perched water table to a minor aquifer and the river. • Space constraints. The preferred remediation approach should have minimal impact on lorry movements or existing structures or hardstanding. A border of landscaping surrounded the site as a border between the operational areas and its neighbours. • Cost constraints. The minimum cost was sought given that costs would impact on profitability, however, some flexibility was agreed given the site’s role as a case study for wider learning within the company. Being able to spread costs, rather than face larger payments in a short period of time was seen as advantageous. Given the urgency of the need to achieve source and odour control, higher ‘up-front’ costs were seen as more or less unavoidable for these actions. 145 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 A series of site specific conditions also affected what remediation approaches would be suitable. These included the site geology and the proximity of sensitised neighbours. The geology indicated that there would be little downward migration as beneath the aquifer was a layer of London Clay. However, lateral migration was likely due to the layer of sand and gravel. The sensitivity of the site’s close neighbours limited the choice of suitable remediation approaches according their capacity to create noise, dust, traffic or additional odour (see section on sustainable development). Risk management Pollutant linkages considered by risk assessment for the site were as follows: Sources Pathways Receptors Diesel in soil, groundwater and as free product LNAPL in the lorry fuelling area, dissolved and possibly sorbed diesel around fuelling area. Groundwater (sand/gravel aquifer); vapour phase in the vadose zone to adjacent garden (hardstanding is channelling vapour to the adjacent garden); direct exposure if anybody dug into the soil; vapours from groundwater. Groundwater, neighbouring residents, site operatives (users and groundworkers). Pollutant linkages were found as follows. Pollutant linkages considered Human receptors: residents • Vapour causing odour nuisance • TPH via soil ingestion Human receptors: current/future site operatives during normal activities of site • Direct contact unlikely due to presence of buildings/hardstanding Human receptors: site operatives during remediation • If groundworks are carried out at any time; operatives could be in direct contact with contaminated materials and health and safety measures would be required. Groundwater receptor • Sand and gravel is classified as a minor aquifer Pollutant linkages present? a s U a a The risk assessment confirmed the objectives that had driven the site investigation and its initial conclusions (see above) and set site-specific target levels (SSTLs) for: 146 • source control; • control of vapour phase in order to ameliorate odour; • elimination of dissolved phase as a liability issue (perceived as well as actual). The SSTLs were based on the TPH working party criteria (www.aehs.org) which divides TPH into fractions based in part on toxicity and fate and transport characteristics. These fractions provide a better basis for risk assessment than considering TPH as a whole and thereby allow a better evaluation of whether remediation is required, and, if so, what the remedial targets should be. Technical suitability Technical suitability was considered in two stages. The first stage was to examine the risk management application and the nature of the contamination problem, as shown below. This first stage would produce a short list of options for more detailed scrutiny, in the light of different stakeholder viewpoints, sustainable development and costs and benefits (see Box 1). Given that the contamination problem was LNAPL based in a shallow sandy gravel aquifer with some potential for vapour phase extraction and a small free product source term, a range of remediation interventions might be considered. As a general strategy shorter term methods would be deployed for source management and odour control, than for dealing with the plume (pathway management). Source management strategies considered were: • Tank and leakage repair: the hardstanding surface was to be repaired and made impermeable, along with an overhaul of the drainage system. Fuel lines were to be pressure tested, and any proving defective were to be replaced, along with the excavation and removal of any obviously contaminated soil associated with the fuel line. • Dual phase extraction (DPE) of the source term would require well points to be drilled through hardstanding in the vicinity of fuel services. Over the period of DPE installation fuelling operations would have to be suspended on the site. Duration of DPE to remove the free phase product was estimated to be 10 to 12 weeks. The DPE would yield liquid NAPL waste, and also potentially contaminated groundwater. • Excavation of the source term would require significant on-site plant and equipment for a short period, estimated to be one week, severely disrupting site operations. Clearly, fuelling operations would cease, but lorry movements would also be impeded. General principles for remedial approach selection Box 1 Risk management application Source control and pathway management (treatment of the dissolved phase and any sorbed contamination outside the free product area), no receptor management. The remediation selected needed to find a balance between limiting source control (because operational site want to minimize excavation; minimize disruption to structures and operations); without leaving too much residual source term as this would extend the duration of the pathway management to beyond five years. Treatable contaminants and materials Diesel in sand and gravel, vapour phase, free product, sorbed phase and dissolved phase. Treatment location On-site treatments were favoured for all risk management actions, to minimize lorry movements/disruption to nearby residents and the disruption to site operation that would result from excavation of the source term. Off-site disposal advantages of speed and flexibility were not judged worth the impact of excavation on commercial activities, even if excavation works could be completed inside five working days. A key issue was the intrusiveness of the solution employed. The company did not want to heighten anxieties or make its remediation project obvious to all site visitors by a very visually intrusive technology. However, it was also anxious to employ a solution that the immediate site neighbours could see and be reassured that action was taking place, but not to the extent that they perceived a more serious problem than actually existed. Outcome/legacy Destruction of contamination was the preferred outcome as it minimized liability for the site owner, reassured the householders that there would be no re-emergence of the problem and was seen as the most sustainable outcome by the regulator, for example avoiding the removal of contaminated soil off site. There was also a significant risk of damage to fuelling installations and other underground services. Pathway management strategies considered were: • air sparging and soil vacuum extraction (SVE) for the plume (pathway management): suitable for diesel range hydrocarbons. SVE suitable for treating the vadose zone (sandy soil). Bioventing would maximize destruction of contaminants in situ, although the vadose zone thickness was relatively small to contain any volatile organic compounds (VOCs) liberated by venting. Air sparging could be relatively difficult to install given the limited depth of the perched aquifer. It would also need to be accompanied with SVE for vapour control. However, modelling indicated that a combination of venting and sparging could prevent the further migration of VOCs over the site boundary within three months; • monitored natural attenuation (MNA) for the plume; modelling indicated that with the LNAPL free product removed, degradation of the dissolved phase to below SSTLs would take two to three years, given the texture of the aquifer, its flow rate and the degradability of diesel range hydrocarbons; • use of a redox ameliorant for the plume was predicted to achieve reduction of dissolved phase contamination in six to twelve months; • pump and treat was discounted as a suitable remediation option given the shallow depth of the contaminated groundwater. Odour management strategies considered were: • an interception trench with passive venting could be placed in the landscaped area between the site and the affected household. This would have an immediate impact on vadose zone migration of VOCs to the affected household. However, the VOCs would be vented to air, and without active extraction and passage of emissions through activated carbon, emissions might be close enough to the household to still cause complaint; • SVE – an additional benefit of SVE was the removal and prevention of further migration of VOCs to the affected household; • DPE – the effect of DPE on vadose zone would also be likely to be effective for odour control. NB: odour control is really a facet of pathway management, but was described separately to make the linkage of possible remediation strategies to desired core objectives more transparent. Odour control may be difficult to achieve in practice, but was a key consideration for the neighbour, the local authority and also of concern to the client as noticeable manifestation of site problems. Stakeholder views The ‘core’ stakeholders for this site were the company who owned the site, the regulators and the affected householder. The company was anxious to achieve a cost effective, but permanent resolution of the problems. The company wanted the cause for complaint (odour) and its source (free product) to be removed as quickly as possible, to prevent a new line of complaint about their site. They wanted the remainder of the remediation carried out so that there would be no per147 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 ceived liabilities within five years. The affected household saw the leak as another example of what they perceived to be generally sloppy management of the site, which added weight to their view that site operations should be controlled more rigorously or transferred elsewhere. They were particularly anxious that as well as a traffic hazard from the site, they were now facing a risk to their health, as well as nuisance odour. One of the householders was a keen gardener, and had objected to the placement of a down-gradient monitoring well on his property, although he had eventually been persuaded to agree to this. The local authority had already warned the site manager about noise and operations outside the limits of the planning conditions on the site, and what was reasonable for a site neighbouring housing. The local authority wanted good evidence that the site owner’s expressed desire to achieve a fast resolution of complaints would result in an effective solution. They preferred the adoption of remediation solutions that were well established in the UK, and felt that the assessment of ‘innovative’ solutions would be more problematic for them. The local office of the Environment Agency was involved because of the affected aquifer, and the need for possible licensing of remediation activities. Both the Environment Agency and the local authority preferred solutions that did not involve the off-site disposal of contaminated soil. Other stakeholders with an interest in the site included the other neighbouring households and many residents in the local area, who had begun to mount a campaign against the lorry traffic using the site. Some neighbouring households wanted to use the odour problem in this campaign, whereas others did not, fearing the effect that might have on their property values. Aside from the immediate neighbours of the site, the majority of local residents were indifferent to the site and its issues, or at least not involved in campaigning. The residents were not too concerned about how the remediation was done, but that it should be a complete solution, and should have the smallest possible impact on them (e.g. no traffic, no noise, no disruption). The local planning department had been consulted by the EHO several times about the site’s planning permission conditions (see above). The local authority had sought advice from the local office of the Environment Agency, who also had a direct interest in the minor aquifer that was a potential receptor. The Agency was anxious for a rapid resolution of dissolved phase contamination, as well as source control. The EHO was anxious for a rapid resolution of the relieving the local odour problem. Sustainable development For this site, dealing with project drivers (i.e. the removal of the source term, the abatement of the odour 148 and the removal of the dissolved/sorbed phase contamination) has certain ‘sustainability value’ – i.e. value in terms of environment, economics and society – that would be similar whatever the remediation approach used – i.e. the ‘core value’ is relatively constant. Clearly the different remedial approaches vary in their wider environmental effects. Some of these effects would be temporary and some permanent. Some would affect the environment locally, others could be considered more global concerns, such as the prevention if possible of off-site disposal of contaminated soil. Some of these wider effects had the capacity to cause aggravation to various stakeholders. A simple matrix was used to consider possible wider environmental effects for each of the possible remediation approaches shortlisted (summarized in Table 5). This considered the following broad categories of effect (based on an Agency Review – see Table 11). The project consultants did not have the resources to complete a detailed assessment of possible wider effects, so based their conclusions on a set of initial surmises. • Aggravation factors: considers environmental impacts which could have a direct and noticeable effect on some stakeholders. In some cases this effect may be more perceived than actual. • Air and atmosphere: considers those impacts on air quality and atmosphere function of emission due to operating the remediation process. • Water function: considers the effects of remediation emissions to surface and groundwaters, although for coastal locations, impacts to estuarine waters should also be considered. • Ground function: considers impacts on the solid subsurface, including impacts on soil water content. Impacts considered include toxic effects, mechanical impacts and changes in soil/ground function. • Legacy: explores how remediation processes vary in their ability to offer a permanent solution to contamination removal and improvement of land quality and to evaluate their long-term impact on the site and the surrounding ecosystems. • Resource and energy use: considers the ‘costs of production’ in non-monetary terms of a remediation scheme. It is separate from other themes, e.g. legacy to make its consideration intuitively clearer. • Conservation: explores the impact of remediation work on ecosystems and features of the environment valued by the community. The consultants for the project also gave brief consideration to wider economic and social effects of the different remediation approaches, as summarized in Table 6. A number of these emerged from the evaluation of different stakeholder perspectives. General principles for remedial approach selection Table 5. Considering the wider environmental effects of the remediation shortlist options Category Aggravation factors The critical factors that would cause annoyance, based on the assessment of stakeholder viewpoints, were considered to be: interference in the affected householder’s amenity (garden!), visual intrusiveness, dust, odour, noise and traffic (not necessarily in order of priority) • Source management: Excavation was considered to have the greatest potential to create noise, traffic, dust and odour albeit for only a short period of time (one week). It was also most visually intrusive, but any impact on the householders’ use of their gardens would be of short duration, and no further installations would need to be put on neighbouring properties. The DPE approach did have the capacity to generate noise over a prolonged period of time, but the DPE supplier suggested that ambient noise from a system properly soundproofed contained in a temporary cabin would not be noticeable during daylight hours. Timed operation might be necessary to avoid disturbance of the neighbours at night. Traffic from the DPE/groundwater treatment installation and dismantling, and for removing collected VOCs (see below) would be minimal. • Pathway management: SVE and air sparging could run in conjunction with DPE and again the supplier suggested that for a properly contained system levels of ambient noise would be low. Well points would not need to extend beyond the site boundary. • Odour control: Excavation of the boundary trench would affect the adjacent household’s view across their garden, until landscaping plants had regrown, or a screen had been planted. SVE and DPE – see above. Air and atmosphere Emission on VOCs to atmosphere (see also ‘odour’ above). • Source management: Excavation would liberate significant VOCs over a short period. DPE would require emissions treatment (e.g. using activated carbon) to recover VOCs. Direct venting to atmosphere was not an acceptable solution for this urban site. • Pathway management: Sparging/SVE would require emissions treatment (activated carbon) to recover VOCs. Direct venting to atmosphere was not an acceptable solution for this urban site. Given the sensitivity of the site and its situation, the local regulator felt that emissions control was necessary to allow bioventing, even although modelling had indicated that using bioventing would be likely to result in very little residual VOCs being liberated to atmosphere. • Odour control: The local regulator was not prepared to accept an intervention trench without some form of limits on its possible VOCs emissions. Modelling indicated that in conjunction with DPE very little emission of VOCs would take place from the interception trench, which also meant that it would have relatively little function in this context. Water function Further migration of the dissolved phase towards the river and changes in aquifer chemistry were to be avoided. Use of local foul sewers for water disposal from DPE was considered following on site treatment. • Source management: The DPE system would remove some groundwater, which would need to be disposed of off site, as the volumes did not justify on site treatment. • Pathway management: None of the pathway management remediation strategies was considered to have a significant effect on the local aquifer, although for the sparging and redox ameliorant technologies some localized effects on pH and redox condition would take place. • Odour control: no effects predicted. Ground function • Source management: Excavation to remove LNAPLs would disturb the ground conditions greatly, but given that the area was mainly hardstanding, this was not considered a significant issue. No detrimental effects from DPE were predicted. • Pathway management: No significant changes in ground conditions (e.g. geotechnical properties, toxic intermediate breakdown products) were predicted for any of the approaches being considered. However, the redox ameliorant would result in magnesium hydroxide and oxide remaining in a number of direct injection points beneath the hard standing. • Odour control: The interception trench would permanently change the nature of the ground conditions of a portion of the landscaped area around the site. Legacy • Source management: DPE and excavation remove the contamination from the site, requiring off site treatment / disposal. The volume of waste material generated by an excavation approach is much greater. Waste material would be landfilled, and hence represent a transfer of contamination from one site to another. Contaminated water from DPE was to be discharged to sewerage. Granular activated carbon (GAC) would require collection and off-site disposal. • Pathway management: With the exception of GAC from SVE off-gas treatment and water from knock-out pots, little waste would be generated by any of the methods under consideration. Nor were any long-term impacts on the site and its surroundings (gardens) considered likely for them. • Odour control: Ditto. Resource/ energy use • Source management: Comparing the fuel likely to be needed for the excavation project, compared with the electricity use of the DPE system, even over 3 months and taking into account energy losses in generation and transmission, indicated that excavation would be a far greater use of fossil fuel. It would also involve a far greater use of plant, equipment and consumable items that could not be recycled. • Pathway management: SVE/sparging would use a significant amount of energy over 3 to 6 months. Injection of redox material would also use energy. The amounts of energy involved were thought to be comparable. However, the energy cost for sparging and SVE was higher. The redox ameliorant process would use a manufactured formulation of magnesium peroxide and other magnesium compounds. The sparging and venting system would use a number of un-reusable manufactured components. Hence they seemed broadly equivalent. Conversely, MNA would use no additional energy or resources on site, although some impact of the studies necessary to collect lines of evidence was possible, similar studies were felt to be necessary for the SVE/sparging and redox ameliorant techniques in any case. MNA would require energy and resource use for monitoring. MNA monitoring and analyses needs were not though to be substantially more onerous than those that would be needed for using a redox ameliorant or SVE. Hence monitoring was not thought likely to affect the resource/energy use ranking. • Odour control: Energy and resource costs of an interception trench could be minimized if this was installed at the same time that the source term was excavated, however, this would give a slight risk of cross contamination of the site. Conservation • Source management: No conservation impacts noted. • Pathway management: No conservation impacts noted. • Odour control: No conservation impacts noted. 149 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Table 6. Considering the wider economic and social effects of the remediation shortlist options Economic effects Some approaches were likely to have a greater disruptive effect on commercial site operations than others, at least on a temporary basis. Some approaches were likely to give more comfort to the affected householder than others and/or to inconvenience him less, most appropriate were approaches based on in situ treatment. The high cost of some options (e.g. DPE) would weaken the economic performance of the company’s operations on that site. SVE/sparging costs are increased because of the need to bury ducting to enable continued use of the site. The possibility of an amicably agreed solution might enhance the company’s profile with local residents and the local community, enabling a more constructive debate (from the company’s viewpoint) about the general operations of the site. Social effects Comfort to the aggrieved stakeholder (affected householder). Visible interventions over a long period (such as SVE/sparging and DPE) might increase public concern about the significance of the contamination problem. Costly interventions affecting company performance on the site could conceivably put jobs at stake, although many in the area want to see the facility closed, it is a significant local employer. Stakeholder preferences (e.g. strong Agency desire for dissolved phase to be resolved as quickly as possible). Costs and benefits The consultants considered two routes to comparing likely remediation costs: 2. 3. • issuing a tender to contractors specifying the site conditions and the shortlist of remediation options, and asking each of the tenderers to provide information about wider impacts and benefits (which could be seen as getting contractors to do the environmental consultants’ job); • following existing Agency guidance on cost benefit analysis (see Table 11); • rank remediation approaches in terms of their ability attain the goals of the project, their wider effects and their cost. 4. 5. The Agency CBA guidance can be followed through increasing levels of complexity depending on need. Four broad themes are set against cost: • • • • human health; environment; land use; and third party or stakeholder concerns. Wider environmental impacts are considered, but not exhaustively. The impacts considered are spread across three of these themes as shown below: • human health and safety: dust, odour, traffic; • environment: impacts on surface and ground water ‘quality’ and ‘quantity’ and the use those waters are put to; local air quality; soil function, habitat and ecology; • land use: impacts on land use for the site and surrounding areas. The Agency guidance adopts a tiered approach to CBA, in five steps, as illustrated in Figure 5: MCA is a means of assigning ‘scores’ to different attributes, and combining those scores in some way that aids a decision (see Figure 6). CEA uses the MCA score divided by remedial option cost as a measure of cost-effectiveness for ranking options. The client, on the basis of consultants’ advice, decided to proceed with a comparison of options themselves to maintain client confidentiality by allowing a narrower tender specification to be drawn for a lesser number of specialist contractors. The consultants decided to use the ranking of shortlisted options rather than the more formal guidance for several reasons. They felt that a more formalized CBA analysis would not be transparent to the local householders, that the guidance did not readily cover all of the wider effects of possible interest, and that it appeared to be relatively time consuming. The different remediation options available for source control and pathway/odour management were initially considered separately, as outlined in Table 7. Indicative costs were obtained for these unit operations. It was immediately clear that the number of combinations that were likely to be used in practice were limited, so a simplified shortlist was agreed upon. 1. 2. 3. 4. 5. 1. 150 screening stages; qualitative analysis; semi-qualitative, using a combined multi-criteria analysis (MCA) and cost effectiveness analysis (CEA) procedure; recommendations for CBA; sensitivity analysis and selection of preferred option. DPE followed by sparging and venting. DPE and use of a redox ameliorant. DPE and MNA. Excavation and removal followed by MNA with an interception trench. Excavation and removal followed by use of a redox ameliorant with an interception trench. General principles for remedial approach selection Screening Qualitative Assessment Cost Effectiveness / Multi Criteria Analysis Formalized Cost Benefit Assessment Sensitivity Analysis Ranking of Preferred Options The decision to use a simple qualitative approach or to move to a more quantitative system will depend on the circumstances of the situation. For example, there may be a clearly preferred option without any need for greater resolution. Whether CBA or MCA is used alone or in combination depends on the specific impacts being evaluated and the availability of valuation data. Feed back into wider selection process Figure 5. Cost benefit analysis approach (Bardos et al. 1999) Figure 6. A general outline of the MCA Method (Bardos et al. 2001) 151 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Table 7. Short-listed remediation options Source control Pathway management Odour management Surface/fuel line leakage repair & replacement as necessary Sparging/SVE Interception trench DPE MNA SVE Excavation and removal Redox ameliorant DPE (from source control) All options would include tank and leakage repair. The indicative costs indicated a synergy between using DPE and SVE, and that SVE alone for a long period would be highly costly. However, it was considered that once the source had been removed by DPE, most of the vapour phase VOCs would also have been removed by SVE, so the process could effectively work in tandem. The ranking of options by cost was found to be that Option 1 was significantly more costly than the other options, which were broadly comparable in cost, although options using MNA were slightly cheaper, i.e.: • Costs of Option 1 >> 2 and 5 > 3 and 4 The overall benefits of achieving the ‘core’ goals for the site included: • effective risk management; • enabling on going commercial operations on site; • reducing liabilities. Each of the five remediation options considered further seemed capable of achieving these core goals within the desired five-year time frame. However, some approaches provided a higher level of confidence that treatment could be achieved within five years. The site owners concern in this regard was that MNA might not fully remove residual liabilities from the site. The Agency desired remediation of the dissolved phase within twelve to 24 months, and were also uncertain that this might be achieved by MNA. Hence, while the technical information was that all options would be effective, the commercial viewpoint was that Options 1, 2 or 5 would be preferred over 3 and 4, given similar costs and wider effects. The wider effects were ranked simply on the basis of the consultants’ knowledge of the remediation technologies, and the key issues that had emerged during the considerations of stakeholder views and sustainable development, as summarized in Tables 8 and 9, as follows: • wider environmental effects: Option 3 (best) > 2 > 1 > 4 > 5 (worst); • wider economic effects: Options 2 and 3 better than options 1, 4 and 5; 152 • wider social effects: Options 1 and 2 (best) > 5 > 3 and 4. The consultants then summarized costs and benefits overall (Table 10) for the client. Overall Options 2 and 3 appeared in the most ‘best’ categories for the various considerations: costs, wider environmental and wider economic effects. Options 2 and 3 were: 2. DPE and use of a redox ameliorant; 3 DPE and MNA. However, both the client and the Agency remained concerned about using MNA on this site. The client wanted an intervention that they felt gave a better guarantee of effective remediation within a five-year time frame. The Agency desired a more rapid treatment of the dissolved phase. It is likely that a higher level in confidence in the likely duration of an MNA based approach could have been gained by further site investigation. However, the incremental costs, and delay to programme, that such a site investigation would incur, were seemed likely to outweigh the slight cost benefit of MNA for this site. Hence, despite the slightly lower costs for Option 3, the client chose to proceed with Option 2: • DPE and use of a redox ameliorant. Technical suitability, Step 2 Before putting out an invitation to tender based on DPE and SVE with use of a redox ameliorant, the consultant carried out a more detailed examination of these technologies to ensure that they were indeed technically suitable for the site in question, and that they were feasible for the site. Obviously, the consultant had a good degree of confidence in the suitability and feasibility of all of the options proposed, but now wished to check in detail against site-specific conditions and implementation. Implementation issues • The site was readily accessible, secure, and fully supplied with services (water, three-phase electricity, gas and sewerage) and manned 24 hours, albeit by security staff only overnight. General principles for remedial approach selection Table 8. Ranking the remediation options by their wider environmental effects Category Ranking Aggravation factors Options 4 and 5 were seen as most problematic given the disturbance of the excavation work, and the nuisance and traffic it would generate, albeit over a short period of time. It was also thought desirable to avoid using an interception trench. Visits to other operational sites had provided assurance that the ambient noise from DPE/SVE/sparging would not be detectable to the site neighbours, nor the company's workers. Hence: Best Options 1, 2 and 3, worst options 4 and 5 Air and atmosphere Direct venting of recovered VOCs to atmosphere would not be permitted, the greatest (albeit short term) source of fugitive emissions of VOCs would be excavation work, hence: Best Options 1 (given the use of GAC), 2 and 3, worst Options 4 and 5 Water function The wider effect on water function for all options was not considered significant, hence: Best all options Ground function Given the commercial use of the site and the existence of hardstanding, effects on ground function were not considered a significant issue, with the proviso that excavation of the interception trench would have a temporary negative effect, hence: Best Options 1, 2 and 3, slightly worse options 4 and 5 Legacy Source management: DPE and excavation remove the contamination from the site, requiring off-site treatment/disposal. The volume of waste material generated by an excavation approach is much greater. Waste material would be landfilled, and hence represent a transfer of contamination from one site to another. Pathway management: No wastes would be generated by any of the methods under consideration. Nor were any long term impact on the site and its surroundings (gardens) were considered likely for them. Odour control: Ditto. Options 1, 2, 3 better than 4 and 5 Resource/energy use Source management: Excavation worse than DPE. Pathway management: SVE/sparging worse than using a redox ameliorant, which is worse than MNA. Odour control: Excavation worse than SVE. Hence, overall: Option 3 (best) > 2 > 1 > 4 > 5 (worst) Conservation The wider effect on conservation for all options was not considered significant, hence: Best all options Social effects Economic effects Table 9. Ranking the remediation options by their wider economic and social effects Disruption Best Options 1, 2 and 3, worst Options 4 and 5 Impact on company finances Best Options 2,3,4 and 5, worst Option 1 Enhancement of profile Properly managed all options were thought to be of possible value to enhancing the company's local profile and reducing tensions with neighbours, hence: Best all options Comfort to householder Best Options 1, 2 and 3, worst options 4 and 5 Visible work Best Options 4 and 5, worst Options 1, 2 and 3 Impact on company jobs Already considered under economic effects Stakeholder preferences Best options 1, 2 and 5 Table 10. Considering costs and benefits overall for the five remediation options Costs Core goals (preference) Wider environmental Wider economic Wider social Best/cheapest 3, 4 1, 2, 5 3 2, 3 1, 2 Mid-ranking 2, 5 Worst/expensive 1 1, 2 3, 4 4, 5 5 1, 4, 5 3, 4 153 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 • Minimal interference with site operations was a key factor. • The site owner and regulator also wanted ease of verification. • The company was anxious to avoid maintaining monitoring on the site for a long period, but equally wanted to be in a position to demonstrate to the local authority and site neighbours that a good quality of remediation had been achieved. • Noise and atmospheric emissions were to be minimised to prevent annoyance to neighbours. • The local Environment Agency welcomed the voluntary remediation and was willing to take a ‘reasonable’ approach to discharge consents. • The remediation design needed to have a degree of flexibility, as while the site had been operated since the 1950s, detailed site records only dated back to the 1980s. • Aftercare needs needed to be the minimum possible to prevent interference with the possible divestment. The key issues emerging from the consideration of implementation issues were that the site had the facilities to support the remediation approach being considered. However, the tender specification would need to ensure that contractors paid close scrutiny to the need for process verification (with the consultant) and ambient noise. The consultant found the following in terms of the feasibility of the components remediation option being proposed: SOURCES OF FURTHER INFORMATION Table 11 lists sources of further information about the various technology selection stages considered in this paper. A wide range of information is available from web links in the UK and overseas covering both technical and policy aspects of the remedy selection processes described in this paper. These ‘web links’ have been compiled on www.nicole.org. DISCUSSION The decision making steps above could lead to some repetition in information collection and analysis. For example, information about ‘driving forces and goals’ will also relate to stakeholder viewpoints. However, in practice, site remediation is multidimensional and iterative in its nature. It is easy to overlook decision making issues, and indeed some such as sustainable development are routinely overlooked (see below). Some, for example drivers and goals, can vary, almost 154 Track record All three technologies (DPE, SVE and the redox ameliorant) had already been used on a significant number of sites in the UK in a successful commercial context. Availability All three technologies had reliable UK vendors and contractors – although a successful tender may have to involve a subcontractor. Validated Validated performance information performance was lacking in the Public Domain UK information for all three technologies. However, extensive performance information was available from the USA, and several contractors would be able to provide confidential information about past applications. The consultant had used DPE and SVE before and so was also fairly confident in their use. The consultant had not used a redox ameliorant before, but saw it as an important emerging commercial opportunity. Verification Verification would be by groundwater monitoring using existing wells, with direct measurement of mass removal by SVE and DPE. Expertise The consultant decided not to use any contractor for whom DPE, SVE or use of a redox ameliorant would be a first time application. Confidence Option 2 represented the best compromise between a technical fit and the clients commercial concerns over residual liabilities. Acceptability The previous analysis of remedial options had shown that the combination of DPE, SVE and a redox ameliorant satisfied the broadest range of stakeholder concerns. as a function of others, for example stakeholder viewpoint. The same applies for technical feasibility. The sequence of issues described above is best thought of as a checklist of general principles, rather than a prescriptive approach. These principles include not just the six broad decision making categories of issues themselves, but also the value in shortlisting options for scrutiny from a stakeholder and sustainable development process, before collecting a full set of decision making information. Throughout, the important watch-phrase is to be aware of what the choice is that is being made, and the minimum amount of information necessary to make it. At a certain point there is enough information to compare alternatives, be that General principles for remedial approach selection Table 11. Sources of further information about remedy selection Drivers and boundaries Model Procedures for the Management of Contaminated Land, CLR11 (DEFRA/Agency – in preparation) Risk assessment/ management ASTM 1995 Environment Agency 1999b Environment Agency 2000b Environment Agency 2002 CLR 7-10, and CLEA software Ferguson et al. 1998, Ferguson and Kasamas 1999 Model Procedures for the Management of Contaminated Land, CLR11 Nathanail et al. 2002 Technical Suitability and Feasibility Environment Agency 2000b Environment Agency Verification Guidance (in preparation) Harris et al. 1995 Nathanail et al. 2002 Suthersan 1996 Sustainable development/ Bardos et al. 2000 wider effects Bardos et al. 2002 CLARINET 2002 Stakeholder views SNIFFER 1999 Costs and benefits Environment Agency 1999a Environment Agency 2000a with a simple ranking approach or a more sophisticated MCA or CBA based analysis. This combination of activities can be made in different ways, and individual categories may be subdivided to make a seemingly more complex analysis. Figure 7 summarizes the general decision making steps likely in the forthcoming DEFRA/Environment Agency ‘Model Procedures’. This flow chart is drawn to emphasize the iterative nature of decision making, and the key question ‘is there enough information’. It proposes a screening to produce a shortlist of options, followed by a more detailed comparison, taking into account technical factors (suitability/feasibility); stakeholder issues (separated as client and legal and ‘other’), sustainable development issues (wider benefits) and a cost benefit analysis. Within the Model Procedures cost benefit analysis is seen as a tool that is parallel to other comparisons such as sustainability appraisal and stakeholder satisfaction. Driving forces and goals Driving forces and goals clearly have a determining effect on the likely remedial approach, and along with the limitations and/or opportunities available for each site, limit the range of feasible remediation responses. They may also determine the risk management approach, and to a large degree set the agenda for discussions between stakeholders, and also what might or might not constitute sustainable development. For many remediation projects remedy selection is on the basis of ‘core’ issues first and wider environmental, economic and social effects second. Risk assessment/risk management Typically risks to human health risk and other receptors are used as a first basis for setting remediation goals. Other decision factors such as technical feasibility and cost are used to select from amongst the suitable remedial alternatives. In cases when the desired level of protection for receptors can not be attained due to costs or technical difficulties in remediating the site, treatment targets may be revisited on a site-specific basis. For many site based problems risk management is the overriding decision making principle, in that particular risk based environmental quality objectives must be met, and then issues such as wider impacts and cost versus benefits considered. However, this sequential approach does not always hold true. In some cases (as described in Bardos et al. 2002) a broad array of sustainable development needs may be considered in parallel with risk management. Two examples follow. • Aquifers can pass through many site boundaries and may be subject to a number of pollutant inputs. In cases where aquifers are used the question may be asked about where an investment is both most effective and most efficient at managing risks. For example, it may be legitimate to consider potable water treatment rather than treating the whole aquifer. In particular following the Water Framework Directive, there is an increasing pressure to deal with aquifer contamination where the aquifer concerned supplies a river basin, even if there is no direct use of that groundwater, to reduce contaminant flux to the river (Harris, reported in NICOLE 2000). In some countries aquifers are considered worthy of 155 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 Figure 7. Schematic for the model procedure for evaluation and selection of remedial measures (draft, DEFRA and Environment Agency in preparation) protection and restoration because they constitute a potential resource. In these circumstances the argument moves from being one of managing risks to human health or protected waters, to one of what is the overall value to society of an improvement in aquifer. It has been argued that for aquifers the value to society of the remediation effect desired, compared with the likely costs of achieving it, should be the fundamental decision making criterion for aquifer restoration (Environment Agency 2000a). ing judgements about future end-use that are in effect dictated by the available solutions, and perhaps also how those solutions themselves might deliver added value. For example, restoration of land for community use may become a tool for social regeneration (Groundwork 2001), or the remediation process itself could be connected with a return of land to some form of economic reuse, for example biomass production (Bardos et al. 2001). • In many countries there are large brownfield areas for which there is no immediate economic driver for redevelopment. Often these are associated with primary and extractive industries that have closed down (Barton 2000; Handley 1996). The local communities in these areas can be deprived compared with the rest of the country concerned. In these situations restoration of land may be supported by public sector funds as a means of regenerating local communities in economic terms and alleviating social problems (Groundwork 2001). Increasingly regeneration of these areas may not be able to rely solely on attracting new economic activity through inward investment (Barton 2000 and 2001). In these situations land restoration planning can therefore be divorced from the fixed views of end use as exemplified by the case study. Again the issue becomes one of looking at the wider value to society of the restoration work, and in particular how this wider value can be enhanced. This may encompass mak- It would not be right to leave the discussion about risk management without explaining how understanding of risk assessment and the capacities of natural systems to effect their own remediation (natural attenuation) has fundamentally modified how remedial techniques can be employed, as described in CLARINET’s philosophy of risk based land management 156 1. Environmental quality criteria should not be viewed in absolute terms. A set of numbers, for example the old ICRCL numbers, can never encapsulate the risk management needs of individual sites. To be fair to ICRCL, they were never intended for this purpose, but acquired it over time, like the chains of Marley’s ghost. It is very easy to take decisions using numbers, and avoid any fundamental understanding of the polluted system. While risk-based decision making means that more grey matter has to be applied to site decision making, it also improves possibilities for General principles for remedial approach selection 2. 3. avoiding unnecessary expenditure and enhances the range of applications for treatment-based approaches. These benefits accrue because the remedial solution has to demonstrate effective risk reduction, rather than compliance with an arbitrary set of numbers. The risk management discipline itself offers a better opportunity to optimize remedial solutions. Using the discipline of site conceptual models and pollutant linkages facilitates the selection of the most appropriate remedial responses. Furthermore, looking at sources and pathways in a holistic sense allows decision makers to determine where the best balance of intensive approaches such as excavation and removal, and cheaper approaches may lie to achieve the optimal risk management benefit for minimum price. The increasing recognition of the role that that old favourite from the waste management sector, natural attenuation, has to play in remediation allows a more elegant, less resource intensive use of remedial interventions. In some cases natural attenuation may be adequate on its own as a risk management strategy. In others a treatment intervention can be targeted so that no more is necessary, than that which allows natural processes to deal with residual contamination. While this approach can be very elegant, it is also critically dependent on a sound understanding of the site (or aquifer) and the processes taking place therein. There is a simple message from these three key developments for treatment-based remediation service providers: there is now a technical rationale for the use of treatment-based remediation, and a clear set of niches for it, defined by the risk management needs of a site, rather than an arbitrary set of treatment goals, or a need to demonstrated remediation of contamination ‘to zero’. Technical suitability and feasibility There are two aspects to the technical fit of any particular solution to a remediation problem: its theoretical fit and its practical fit for the particular circumstances of the project being considered. This paper describes these two aspects as ‘suitability’ and ‘feasibility’, respectively, although this may be rather stretching the dictionary definitions of both words. This distinction is important because the practicality or ‘feasibility’ of a proposed solution may be heavily dependent on a range of nontechnical issues and subjective perceptions. In other words a proposed solution, while being appropriate in every sense from its risk management effectiveness to its ease of implementation on site may be unacceptable for reasons such as its lack of proven track record, even if proven in other countries. It is at the stage of considering technical suitability that it is likely that the most expensive information will be needed, for example measurements that might affect its engineering, for example measurements of groundwater redox or an in situ biological treatment or MNA approach. Often these measurements will necessitate further site visits, data collection and modelling, and intrusive sampling and analysis of collected samples. It is therefore sensible to make a first cut of possible remedial solutions (a shortlist) on the basis of outline information. Some of the shortlisted options may well turn out to be unsuitable on the basis of considerations of cost, stakeholder viewpoints or sustainable development, or infeasible for reasons such as lack of a credible service provider. It is more cost-effective to discount these options before, rather than after, detailed site information has been collected. In the rather simple case study above, the shortlist was whittled down, using a very simple CBA, to one in a single iteration, on the basis of readily available information and reasonable assumptions, without the need to collect further detailed information. Of course, many remediation problems will be more complicated. For example, there may be several parallel pollutant linkages and many source terms. There may be a range of options whose merit is not so clearcut to decision makers. It may be that some stakeholders demand a higher standard of evidence. It is for this reason that guidance such as RBCA and the Model Procedures include elements of iteration, and a more phased approach to decision making, rather than a single shortlist and ranking based CBA. However, the fundamental decision making issues and processes remain the same as those illustrated by this case study. Stakeholders The view of core stakeholders, such as the site owner, service provider and regulator, for example, does of course control remediation decision making. However, the views of other stakeholders can also be critical. In particular, one cannot assume that because the ‘technical’ community accepts risk management, pollutant linkages and site conceptual models that all stakeholders will. Stakeholders may disagree about any aspect of the remediation decision making, from the goals of the project, through risk management considerations, to technical suitability, sustainable development and the cost benefit assessment. A clear, reproducible and documented approach to decision making is therefore necessary, for example a simple ranking approach like the case study, or the more sophisticated Model Procedures and their supporting guidance on cost benefit assessment. 157 Land Contamination & Reclamation / Volume 10 / Number 3 / 2002 NICOLE suggests that in circumstances when not all stakeholders readily agree to a proposed solution, overall agreement depends on maximizing the issues where common ground can be found, and for the others, finding a way forward where there is an agreement to disagree. The alternative is a project that is stalled, leading to an ongoing environmental and cost impacts. All stakeholders must be prepared to ‘bargain’ as part of their contribution to decision making (NICOLE 2001). This means that stakeholders need to take part with some flexibility to ‘manoeuvre’. Unfortunately, there are those who approach remedial decision making from a very fixed standpoint. There are also those who may not accept risk management as a basis for decision making. While risk management offers a tool to examine the optimal remedial solution, this optimum can only be reached if all stakeholders are prepared to engage constructively, and with some flexibility, but always bearing in mind the objective of effectively managing pollutant linkages. Furthermore, the temptation to adopt a sub-standard solution, because it is the only one all stakeholders can agree on, should be avoided. Sustainable development Sustainable development criteria are not very widely used in contemporary contaminated land decision making. Yet as the case study illustrates, it is not necessarily an expensive analysis to carry out, and it can help greatly in addressing differences in points of view between stakeholders. It may be particularly useful in managing a campaigning organization by illustrating the broader impacts of what might initially be seen as ‘greener’ solutions. And it is helpful in simply helping a local authority demonstrate sustainability in its planning control work. Not surprisingly, given the importance of resource utilisation in sustainable development, ‘sustainable’ approaches can also be cost effective. If the two paragraphs above are the ‘carrot’ to encourage more frequent use of sustainable development criteria in remediation decision making, the stick is that achieving sustainable development is an underpinning facet of environmental policy overall. Consequently one can expect an increasing regulatory requirement to demonstrate that remediation projects have been carried out in a sustainable fashion. This is not a million miles away form the ‘Best Practical Environmental Option’ approach used in waste management decision making. Cost benefit analysis Contaminated land decisions must reduce very complex information to a relatively simple set of options with relative advantages and disadvantages. Cost bene158 fit analysis is the tool by which this is done, taking a very wide definition of CBA to encompass a holistic decision making approach. In practice formal and semiformal cost benefit analysis approaches never take all decision making criteria that might be important into account. This is because some criteria simple cannot be quantified (or semi-quantified) in money terms, or the reduction process is so complex as to render it very unclear to the majority of stakeholders involved in a decision. No decision maker should be in the position that they are taking an expert’s word for it! Rather, most decision makers have to consider a rather impure kind of CBA where techniques like MCA may be used as a decision making aid, but values are not necessarily quantified in cash terms. Of course, in very simple scenarios, like the case study above, a simple ranking approach may be adequate to fully explore and document a decision. However, a ranking does not easily allow stakeholders to attach values or measures of relative importance for different criteria. Multicriteria analysis sounds very grand, but as illustrated above, it is simply a system for keeping track of valuations and weightings (measures of importance) used in decision making. It should not be seen as a ‘black art’, but should be open to all to add clarity (rather than darkness) to the decision making process. None of it is ‘rocket science’. CONCLUSIONS Decision making for land remediation boils down to a consideration of six basic principles: the reasons for the remediation work and any constraints on it: • • • • • risk management effectiveness; technical suitability and feasibility; stakeholders’ views; costs versus benefits; and sustainable development, i.e. wider environmental, social and economic impacts. While there is a range of decision support guidance available, it is all based on these basic principles, although approaches some may be more complete in their coverage than others. ACKNOWLEDGEMENTS This work draws on the work of CLARINET (the Contaminated Land Rehabilitation Network For Environmental Technologies in Europe). Paul Bardos’ participation in this network was supported by the Land and Soils Research programme of the Department for General principles for remedial approach selection Environment, Food and Rural Affairs (DEFRA). The paper also draws on lectures from the MSc on Contaminated Land Management held with LQM at the University of Nottingham, and on project work carried out by Arcadis and LQM. However, the views expressed here are those of the authors alone and should not be assumed to reflect the views of the Agency, Arcadis, DEFRA, LQM or the University of Nottingham. 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The views expressed in this and all articles in the journal Land Contamination & Reclamation are those of the authors alone and do not necessarily reflect those of the editor, editorial board or publisher, or of the authors‘ employers or organizations with which they are associated. The information in this article is intended as general guidance only; it is not comprehensive and does not constitute professional advice. Readers are advised to verify any information obtained from this article, and to seek professional advice as appropriate. The publisher does not endorse claims made for processes and products, and does not, to the extent permitted by law, make any warranty, express or implied, in relation to this article, including but not limited to completeness, accuracy, quality and fitness for a particular purpose, or assume any responsibility for damage or loss caused to persons or property as a result of the use of information in this article. 160 View publication stats
