The Extent of Contaminated Land Problems and the Scientific Response

SIMON J.T. POLLARD, MALCOLM LYTHGO AND RAQUEL DUARTE-DAVIDSON

1 The Origins of Contaminated Land Problems

Background

The remediation and redevelopment of contaminated land is widely acknowledged as a major challenge for modern society. Land, and the groundwater below it, used for siting industrial facilities or for waste disposal may be contaminated and its redevelopment often requires that unacceptable risks are assessed and managed so that the site becomes suitable for its new use. Over the years, development planning, corporate environmental auditing and environmental regulation have all contributed to the discovery and subsequent remediation of contaminated land and groundwater. Successful management of contamination, whether at the site, regional or national scale, relies on understanding and applying a large and multidisciplinary knowledge base that straddles the natural, physical, engineering and social sciences within a practical, commercial and regulatory context. Practitioners applying this knowledge work within a decision-making context far removed from that of the research environment. This said, practitioners and decision-makers are required to consider the significance of the science base that affects their decisions, particularly those aspects relating to the perception of risk, the environmental fate of contaminants, the capabilities of analytical science, the concepts of environmental exposure and the practical capabilities of remedial technologies.

Decisions about contaminated land involve a multitude of stakeholders. New mechanisms and skills are required for engaging and involving audiences not familiar with the technically orientated language of environmental risk. The sustainable development policy agenda is resulting in new ways of thinking about risk, technology and decision-making. Increasingly, approaches to site remediation are being scrutinised by reference to their full life-cycle costs, and social, economic and technical factors are being considered alongside one another in appraising risk management options. Industry, its professional advisors and environmental regulators are now having to consider afresh how these broader aspects can best be incorporated into decisions.

A vast literature has developed on the issue of land contamination and several excellent reports, texts and reviews exist that focus on historical perspectives, policy and legal developments and consulting best practice. Here, we introduce the origins and extent of the problem and, as a contribution to the debate over effective solutions to this environmental challenge, we highlight some of the recent developments in the science base that underpin management decisions on land contamination. Given the emphasis in later chapters, we have concentrated on the assessment of contaminated land and research in the open literature. Specific developments in risk assessment, remediation, impacts on human health and the policy and regulatory frameworks are provided in detail elsewhere within this volume.

Origins

The challenge of managing contaminated land is not a new one. It has been recognised by governments internationally for at least thirty years and is closely associated, technically and legislatively with the issues of waste and hazardous waste disposal, the regeneration of derelict land, groundwater pollution and industrial site decommissioning. Whilst legislative boundaries and specific definitions may apply to these activities separately, these issues continue to overlap to a large extent and an examination of the origins of the problem needs to reflect on the historical emergence and development of this set of issues on the socio-economic and political landscape.

The widespread reporting of individual incidents and near misses associated with land contamination, coupled with increased government interest in waste management during the 1970s and 1980s led in many countries to the development of new legislative controls dealing with historically contaminated land and preventing future land contamination (see chapter by Lowe and Lowe). Highly publicised and often referred to international incidents such as those at Love Canal in the United States and Lekkerkerk in the Netherlands resulted in increased public and political interest. A growing concern over waste management practices together with a realisation of the practical and technical difficulties of redeveloping past industrial land have also fuelled the debate. In the United Kingdom, a watershed was the publication of the 1990 House of Commons Environment Committee report on contaminated land, which itself had been prompted by previous Commons and House of Lords committee reports on toxic waste and hazardous waste disposal.

The modern origins of the problem, however, begin with industrialisation, development of the fossil fuel-based economy and growth of the downstream chemical, heavy engineering and manufacturing industries from the 1800s onward (Table 1). Coal gas production and later petroleum refining, together with the steel and chemical industries (e.g. dyestuffs, wood preserving, chloralkali), whilst bringing benefits to society often left a legacy of environmental contamination in an era when a different philosophy prevailed over environmental protection. Table 1 lists some common contaminants and their related past industrial land uses and processes. On- and off-site disposal of industrial wastes, by-products and production residues was commonplace and in some circumstances considered, at the time, to be beneficial. For example, using process residues to raise land levels on floodplains created land for development with a reduced flood risk.

2 The Extent of the Challenge

The Nature of Contaminated Land Problems — the Issue of Definition

It is not a simple matter to define contaminated land, or to categorise degrees of contamination. Setting aside natural contamination, there is, in practice, a continuum of land contamination that results in a range of impacts, from the acute impacts of specific sites, through varying degrees of diffuse, more chronic effects of large areas, through to pristine, uncontaminated land. There is little land in the United Kingdom (UK) that has not been subject to some degree of contamination, albeit by long-range aerial deposition. There are differing views internationally on how much of this continuum should be considered as 'contaminated', by reference to pristine and/or background concentrations and the significance of the concentrations found. The UK has adopted an approach based on how suitable land is for its current or intended use. Land not suitable for use is considered to be so contaminated that it needs to be remediated. This approach works well on a site-specific basis, but the definition can be problematic when trying to scale up for national estimates.

There are several terms in use to describe land in need of remediation. Although the terms may be similar, there are fundamental differences. Figure 1 illustrates the relationships between these terms. The term derelict land, for example, refers to 'land so damaged by past activities that it is incapable of beneficial use without treatment'. The statutory definition of contaminated land in the UK is given in Part IIA of the Environmental Protection Act 1990 (see Lowe and Lowe), that is:

"'Contaminated Land' is any land which appears to the local authority in whose area it is situated to be in such a condition, by reason of substances in, on or under the land, that

(a) significant harm is being caused or there is a significant possibility of such harm being caused; or

(b) pollution of controlled waters is being, or is likely to be, caused"

This statutory definition covers largely those sites at the chronically contaminated end of the continuum and relies on an assessment of the significance of the risks posed by the contamination at the site-specific level. An identified level of a particular contaminant may pose a significant risk of harm at one site with a sensitive land use, such as housing, but not at another less sensitive site, maybe where the land is used for parking. The same principle applies to the pollution of controlled waters, depending on the sensitivity of the receiving water. It might be argued that more general definitions would assist an understanding of the problem at the national scale, but generic descriptions without reference to the site-specific nature of the problem could undermine the risk-based approach and introduce blight on land values or saleability.

Extent and Significance

To date, there has not been a national survey of contaminated land, but there are provisions in recent legislation for the environment agencies to report on the state of contaminated land in the UK and there is in hand work to produce a National Land Use Database (NLUD) that will provide estimates of the extent of derelict land. Current estimates of the extent of contaminated land in England and Wales range from 50 000 to 200 000 ha. This is thought to represent approximately 100 000 contaminated sites, of which the Environment Agency estimates that between 5000 and 20 000 sites may require remediation because they pose an unacceptable risk to human health or the environment. In 1998, the Welsh Office identified 949 contaminated sites in Wales, covering 4100 ha using a definition of contaminated land that excluded sites in active use, or those smaller than 0.5 ha. In 1998, the Scottish Executive estimated that there were 3458 ha (52%) of derelict and vacant land that was known or suspected to be contaminated in Scotland and that the contamination status of a further 5553 ha was unknown.

Estimates of the extent of contaminated land in the United Kingdom are often based on different definitions and therefore need to be viewed cautiously. They are often based on available but incomplete sources and they may mix between definitions. Further, some industry sectors have better information on the impact of their activities than others, and this might be misconstrued to imply that these sectors have caused more contamination. It is hoped that the provisions of the new contaminated land regime in the UK will refine and improve our estimates.

3 Developments in the Science Base

Developments in Environmental Science

From the first stirrings of political interest in contaminated land there has been a response from the scientific communities in terms of research output. Through the translation of research to the field, environmental science continues to underpin and contribute substantially to the practice of managing land contamination (Table 2). For example, our understanding of the fate and transport of contaminants in the environment has shaped our view on where and how to analyse for them, the exposure pathways associated with various classes of compounds and the technologies best suited to managing the risks posed. The interdisciplinary nature of environmental science allows us to cross-fertilise between disciplines, for example, in applying analytical techniques used for petroleum exploration to the characterisation of oil contamination at sites or the application of process engineering design to remedial technology optimisation. Similarly, developments in the social sciences, not least with respect to risk perception and the communication of risk, are forcing a reappraisal of how we involve others in the process of managing land contamination.

A developing theme throughout the last 30 years has been the assessment, characterisation and management of risks to human health and the wider environment from contaminated sites. Once it became clear that many environmental contaminants were ubiquitous at concentrations of parts per billion and less, a need developed to establish levels of significance for the potential risks posed by non-zero concentrations. The risk assessment/risk management paradigm, adapted from the pharmaceutical and nuclear sciences, has since developed to a point whereby it has become a central point of reference for much of the supporting science and the basis for public policy and environmental regulation on contaminated land. The application of risk assessment to contaminated land problems has inevitably highlighted issues of risk acceptance, the tolerability of risk and of equity.

Addressing Social Issues

Concerns over the potential risks to human health from exposure to contaminated soils have fired a broader debate over the wider social impacts of contaminated land on the quality of life. Many former industrialised areas form a focus for low cost or social housing, driven partly by positive issues such as access to work opportunities and partly by negative issues such as low land values. Some of the more deprived communities have resided in these contaminated areas. In addition to this social issue of environmental justice, a wider recognition of the importance of a sense of place and community attachment, and a broader interpretation of 'environment' beyond the strictly technical one, are bringing issues like the value of urban ecology, the importance of industrial heritage and the need for wider stakeholder involvement to the fore.

A move to more inclusive processes for environmental decision-making is emerging, influenced in part by 30 years of risk communication literature and by placing social progress centre stage in the strategy for sustainable development. The regeneration of contaminated land has always required a multi- and trans-disciplinary approach, but increasingly scientists, engineers, planners and lawyers are turning to the social sciences for a re-interpretation of the issues historically viewed as driven by technological and economic concern alone. As a result, we are gaining valuable insights into the value of institutional trust, into 'process' issues in terms of involving others in decision-making, into issues of equity and the perceptions and reporting of risk. This work now needs to be integrated within the existing management frameworks for contaminated land management.