Remedial Approach Selection: Principles & Case Study

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General principles for remedial approach selection
Article in Land Contamination & Reclamation · July 2002
DOI: 10.2462/09670513.614
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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.
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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)
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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
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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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