Contaminated Land and its Reclamation: Volume 7 (Issues in Environmental Science and Technology) - Softcover

Softcover

ISBN 10: 085404230X ISBN 13: 9780854042302

Publisher: Royal Society of Chemistry, 1997

Synopsis

An authoritative treatment of each of the topics is ensured by the particular expertise and distinction of the authors.

About this title

About the Authors

Ron Hester is an emeritus professor of chemistry at the University of York. In addition to his research work on a wide range of applications of vibrational spectroscopy, he has been actively involved in environmental chemistry and was a founder member of the Royal Society of Chemistry’s Environment Group. His current activities are mainly as an editor and as an external examiner and assessor on courses, individual promotions, and departmental/subject area evaluations both in the UK and abroad.

Roy Harrison OBE is Queen Elizabeth II Birmingham Centenary Professor of Environmental Health at the University of Birmingham. In 2004 he was appointed OBE for services to environmental science. Professor Harrison’s research interests lie in the field of environment and human health. His main specialism is in air pollution, from emissions through atmospheric chemical and physical transformations to exposure and effects on human health. Much of this work is designed to inform the development of policy.

Excerpt. © Reprinted by permission. All rights reserved.

Contaminated Land and its Reclamation

By R. E. Hester, R. M. Harrison

The Royal Society of Chemistry

Copyright © 1997 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85404-230-2

Contents

Overview: Context, Calculating Risk and Using Consultants Peter J. Young, Simon Pollard and Phillip Crowcroft, 1, 
UK Government Policy and Controls Mary R. Harris and Judith Denner, 25, 
Remediation Methods for Contaminated Sites Peter A. Wood, 47, 
Land Reclamation after Coal-mining Operations David L. Rimmer and Alan Younger, 73, 
Remediation of Lead-, Zinc- and Cadmium-contaminated Soils Michael Lambert, Gary Pierzynski, Larry Erickson and Jerry Schnoor, 91, 
Risk Assessment and Management Strategies Gwyn Griffiths and Steve Smith, 103, 
Legal Liabilities and Insurance Aspects of Contaminated Land Anthony J. Lennon, 125, 
Subject Index, 141, 

CHAPTER 1

Overview: Context, Calculating Risk and Using Consultants

PETER J. YOUNG, SIMON POLLARD AND PHILLIP CROWCROFT

1 Introduction

Historical Perspectives

The presence of land contamination is an inevitable legacy of an industrial past. At least since the time of Roman lead mining, the UK has seen human activities leave naturally present contamination concentrated, or altered in its chemical form. Since the industrial revolution of the late 18th century, an increasing range of new compounds have been manufactured and added to the list of contaminants, and the affected area of land has increased dramatically. Current estimates suggest between 100 000 and 220 000 ha of land is contaminated, representing between 0.4 and 0.8% of the total UK land area. Table 1 sets out the principal types of contamination and its typical severity for major industrial land uses, based on results from more than 500 site-based studies.

Much uncertainty over the presence of contaminated land is derived from the lack of a consistent definition. Other designations of land such as vacant, derelict, industrial or damaged can be confused with evidence for contamination. Contaminated land is not the same as derelict land; nor is the term contaminated land applied in the strict scientific sense of indicating the presence of an introduced substance which is harmful. If the substance is harmful, it is a 'pollutant'.

The Department of the Environment (DoE) has described contaminated land as 'land which represents an actual or potential hazard to health or the environment as a result of current or previous use'. Contrast this with derelict land which is 'land so damaged by past activities that it is incapable of beneficial use without treatment'. Clearly the two are independent. A worked-out limestone quarry may be derelict but will not be contaminated. In contrast, many established chemical factories will be contaminated but not derelict. Contaminated land poses a potential threat to the environment, but derelict land is a threat to future development, although it may be aesthetically unattractive as well.

Against this complex background of definition, the public, and financial markets, became alerted to land contamination by a sequence of well publicized incidents in the 1980s and early 1990s (Figure 1). At this time, investigation for soil and groundwater contamination was merely costed for in the purchase of land for redevelopment, and prior investigation was frequently patchy or non-existent. Three events which were influential in focusing concern about contaminated land are summarized in Table 2.

These and other sites were described to the House of Commons Environment Committee in 1989 and their report, published in 1990, called for registers of contaminated land to be established. This greatly influenced DOE thinking on the Environmental Protection Act, which was at the final drafting stage. The DOE had previously aimed to provide guidance to developers through advisory limits for concentrations of contaminants through publications from the Interdepartmental Committee on the Redevelopment of Contaminated Land (ICRCL). The idea of registering known or potentially contaminated land was more interventionist and, if not handled extremely carefully, could blight urban areas where redevelopment and investment is most needed.

In 1990, the DOE published the Government's response to the Environment Committee. Linked to this were three actions which injected momentum into the field of contaminated land assessment:

1. A provision (section 143) was made in the Environment Protection Act 1990 for regulations requiring local authorities to compile registers of potentially contaminated land.

2. The DOE initiated a process of consultation on registers and contaminated land policy.

3. The DOE began to expand its research programme to provide broader guidance on contaminated land.

Once a proposal for registers of potentially contaminated land was incorporated in legislation, a lengthy and active debate was triggered. The Government sought to focus and inform this debate by a series of consultation papers as new policy was developed. The DOE also informed itself through international liaison where alternative approaches have been offered, many of these coming under national criticism over expense or quality of environmental protection. An interpretation of the key points emerging during this debate is offered in Table 3. In understanding the current legislative position on contaminated land it is important to have regard to this recent period of debate and uncertainty, with the emergence of a true risk-based approach founded on firm scientific and toxicological principles. Further detail on the current regulatory framework and its foundation on risk assessment is given in Section 3.

Current Consequences

The current position with contaminated land is largely attributable to the response from Government, and more widely to the concerns highlighted at the beginning of this decade. These have led to a radical and rapid change in the technical approach to evaluating and remediating contaminated land. The routine introduction of risk assessment, a phased and chemically orientated approach to site investigation, and the selection of remediation strategies from more technologies than simple cap and cover systems are all rapidly developing areas described below in Sections 3–5. Underpinning these developments have been the changes in the legislative position, the growth in research based guidance, particularly from DOE, and the availability of specialist expertise from environmental consultants (see Section 6).

From a technical viewpoint, recent developments have been extremely beneficial. The complexity of evaluating contamination has been thoroughly exposed, and the risk associated with facile and inadequate approaches prevailing in the market place has been much reduced. The prospect of new guidance values for key contaminants which take account of the availability, toxicity, pathway and impact of the contaminant will be a significant improvement over existing ICRCL guidance. However, the draft guideline values only address human health. Separate and additional assessment techniques are required for ecological, phytotoxic and physical damage potential. The link has also been made between the soil and water environments, so that contaminated land assessment and remediation should succeed in addressing all potential impacts in one overall risk-based approach. Such an integrated approach places new demands on the quality of the advice available on contaminated land. Awareness of the rapidly developing technological base is required, whether in investigation, risk assessment or remediation. A common understanding and language must be used to transfer knowledge clearly between chemists, engineers, environmental scientists, chartered surveyors, developers and lawyers, to name a few of those whose skills are needed to deal successfully with contaminated land. It is against this background of escalating demand that this article has been produced.

2 Identifying Contamination

To contaminate is defined as 'to make impure or pollute' in the Oxford English Dictionary. For the purposes of dealing with land, contamination is now taking on a dual meaning. The first is defined by legislation in the Environment Act 1995, and relates to the potential to cause significant harm to humans or pollution of controlled waters. In a wider sense, however, contamination may be viewed as a condition whereby soil or water contains above background concentrations of substances which are not normally there. These can be both chemical and physical, but for the purposes of this review, chemical contamination is most relevant.

Defining soil as contaminated is not merely a question of whether a chemical substance, say cadmium or phenol, is present, but whether it is present in sufficient quantity to cause harm. In relation to the Environment Act 1995, harm is defined, inter alia, as death, serious injury, disease, genetic mutation or birth defects. A great deal of cadmium or phenols are needed in soil to cause death and, furthermore, death will only occur if the soil is ingested in large quantities. So this raises the question of whether the mere presence of a chemical in soil at high concentrations is contamination. The answer in the UK is that such soil is contaminated, but the land would only be defined as 'contaminated land' under the regulatory regime if harm was occurring or likely to occur.

Clearly then, contamination of soil or water may exist, but if it is not causing harm it is possible to consider leaving it alone until such time as a particular site needs to be developed or reclaimed.

Contamination can create a range of hazards, depending on its composition and nature. It may be present in solid, liquid or gas phases, and may be physical, chemical or biological. Contaminants that are hazardous to humans are not necessarily hazardous to building materials or flora. Hazards may include:

• carcinogenicity

• toxicity

• asphyxiation

• corrosivity

• phytotoxicity

• combustibility

• explosivity

• radioactivity

The process of assessing whether the existence of contamination matters is termed risk assessment. This is discussed more fully in the next section. Of prime importance in carrying out a risk assessment is the need to identify what or who is at risk, and these risk groups are termed targets or receptors. They comprise the following:

(i) People

• adults

• children

• site workers (temporary and permanent)

• permanent residents

• visitors

• neighbours

(ii) Water resources

• surface water

• groundwater

(iii) Flora and fauna

• sites of special scientific interest (SSSIs)

• livestock and wild animals, birds, etc.

• landscaping

• foundations

(iv) Buildings

• services

• structures

It should be remembered that not all the above receptors will exist at all locations, and part of the risk assessment process will be to define site-specific receptors.

3 Risk Assessment

Principles

With introduction of the new regulatory regime for contaminated land in section 57 of the Environment Act 1995, the UK has endorsed a risk-based framework within which contaminated land can be identified, assessed and managed. This framework adopts a rationale and terminology from accepted international approaches to the regulation of environmental media and it embodies the fundamental distinctions between toxicity, hazard and risk that exist throughout environmental science. These terms are defined below:

• toxicity: the potential of a material to produce injury in biological systems

• hazard: the nature of the adverse effect posed by the toxic material

• risk: the probability of suffering harm or loss under specific circumstances

The term 'risk' has a multitude of uses and is not to be confused with 'hazard'. In the context of contamined land, the term 'risk' is used widely across disciplines when referring to issues such as first and third party financial liability, risks to human health and the environment, the perceived consequences of chemical exposure and the operational risk of project over-run. There is always a requirement, therefore, to state clearly what form of risk is under consideration and what its components are.

In terms of contaminated land, risks to human health and the environment can be regarded as being comprised of the following components:

• a source: a toxic substance or group of toxic substances with the potential to cause harm

• a pathway: a route by which a receptor could be exposed to, or affected by, the toxic substance(s)

• a receptor: a particular entity which is being harmed or adversely affected by the toxic substance(s)

Hazards arising from chemical exposure are characterized specifically by the nature of the adverse effect, the receptor and the target they affect; like physical hazards, they can only be realized where there is a 'linkage' between the source, the pathway and the receptor. The probability of a hazard being realized, i.e. the risk, depends on the context of this linkage, including site-specific factors such as the contaminant concentration in the exposure medium, its bioavailability, the ease of access to the exposure pathway and the duration of exposure. The consequences of the risk under consideration depend on site-specific factors such as the toxicological potency of the contaminant being considered, the specific adverse effect on the receptor, the duration of exposure and the sensitivity of the receptor (e.g. child versus adult, sites of special scientific interest (SSSIs) versus unprotected ecosystems of low sensitivity).

Risk Assessment. The process of risk assessment can be defined as simply 'an evaluation of the probability of harm' and, in the context of contaminated land, is concerned with gathering and interpreting information on the characteristics of sources, pathways and receptors at a specific site and understanding the uncertainties inherent to the ensuing assessment of risk. The requirements of the risk assessment set the scope of a site investigation and, together, these activities form the scientific part of the contaminated land investigation. In practice, this involves characterization of the environmental chemistry of the contaminants, relevant properties of the soil(s) encountered and the wider site characteristics that influence contaminant fate and transport.

The environmental properties of chemicals encountered at contaminated land sites (Table 4) determine the distribution, fate and transport of the contamination and play a major role in determining:

(i) the suite of chemical analyses undertaken as part of the site investigation

(ii) the exposure assessment component of the risk assessment

(iii) the screening of remedial technologies

Because soil is itself a multi-media environment comprising solid, liquid, gaseous and biotic components, understanding the relative distribution and flux of contaminants between these components is an essential prerequisite to the site investigation, risk assessment and remedial plan. For example, the 4-6 ring polynuclear aromatic hydrocarbons (PAHs) possess very high soil organic carbon-water partition coefficients and remain predominantly adsorbed to the solid soil matrix. Therefore, where high molecular weight PAHs are of concern, analytical efforts focus on soil-bound PAH; the exposure assessment centres on pathways that involve the ingestion and inhalation of soil particles; and the remedial plan considers specific technologies that treat the soil matrix, such as soil-phase bioremediation.

The process of risk assessment 14 can be viewed as consisting of four key stages:

• hazard identification (what are the hazards presented by toxic substances at the site?)

• exposure assessment (what are the key environmental pathways and exposure routes by which the toxic substances can reach the receptors and, if required, what are the concentrations of substances at the point of exposure?)

• dose-response assessment (how potent are the toxic substances that can reach the receptor?)

• risk characterization (what level of risk can be assigned to each source-pathway-receptor linkage?)

Methodologies for contaminated land risk assessment vary widely between practitioners and jurisdictions but can essentially be categorized as qualitative, semi-quantitative and quantitative in their approach. In most cases, a qualitative assessment of risk is sufficient to identify the key issues at a contaminated site, providing it includes the full range of toxic contaminants encountered, takes account of direct and indirect exposure pathways and considers relevant receptors on and off the site.

Where the source–pathway–receptor linkage is established, the qualitative approach can usefully provide an initial ranking of risks as insignificant, low, medium and high, depending on the site-specific factors mentioned above. These obviously are subjective designations and would require their own criteria in order to achieve uniformity of approach between sites (Table 5). Within the context of a tiered approach to risk assessment, semi-quantitative and quantitative risk assessment (QRA) methodologies are reserved for situations where greater resolution is required between risks in order to select between risk management options. QRA has become a highly specialized tool that relies heavily on the expert understanding and interpretation of baseline toxicological data. It can be applied only where contaminated sites are very well characterized and hazards are well defined (e.g. sites with radioactivity).

Risk Management. Risk management involves 'the evaluation of alternative options taking into account available economic, regulatory, political, social, scientific and technological information in order to select the most appropriate means of reducing risk' (adapted from La Grega et al.). In practice, risks are managed by isolating or removing contaminant sources, intercepting exposure pathways or isolating or removing receptors; the guiding principle is to break the source–pathway–receptor linkage. The process of risk management employs the scientific output of the risk assessment, but considers other factors such as the financial and technical feasibility of remedial technologies, planning constraints and risk perception issues.

(Continues...)

Excerpted from Contaminated Land and its Reclamation by R. E. Hester, R. M. Harrison. Copyright © 1997 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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Edition details

• Publisher: Royal Society of Chemistry
• Publication date: 1997
• Language: English
• ISBN 10: 085404230X
• ISBN 13: 9780854042302
• Binding: Paperback
• Number of pages: 160
• Editor: Hester R E, Harrison R M