Land Remediation

Protocols

Recommended Guidance and Checklist for Tier 1 Ecological Risk Assessment of Contaminated Sites in British Columbia

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Chapter 1 - Introduction

1.0 INTRODUCTION

1.1 Scope and Organization of the Document

1.2 The Basic Framework for Ecological Risk Assessment

1.3 Regulatory Context, or How Did I Get to the Risk Assessment

1.3.1 Deciding if a site is contaminated

1.3.2 Remediation options 1-6

1.3.3 Monitoring a site after cleanup 1-7

1.4 What is the checklist 1-7

1.5 Use of the checklist

1.0 INTRODUCTION

1.1 Scope and Organization of the Document

This document provides specific guidance on how to perform screening (Tier 1) ecological risk assessments (T1 EcoRA) for sites within the Province of British Columbia. A number of ecological risk assessment framework, issue, and guidance documents have been prepared by a variety of agencies in North America. These are written primarily for specialists in the field of ecological risk assessment and do not give specific recommendations, although all have similar themes. The purpose of this document is markedly different, although based on the framework prepared by Environment Canada (CCME, 1992).

This document provides a checklist for the performance of T1 EcoRA in the Province of British Columbia as regulated and enforced by the British Columbia Ministry of Environment (BCE). It is intended to promote consistent and technically defensible T1 EcoRA 's under BCE's Contaminated Sites Regulation (BCE, 1996a). The document is for use in conjunction with the procedures for human health risk assessment at contaminated sites recommended by BCE.

Ecological risk assessment is an interdisciplinary field that draws on concepts, data, models and opinions from environmental toxicology, ecology, physiology and environmental chemistry, as well as other scientific disciplines such as mathematics. It is important to recognize that ecological risk assessment is a complex and nonlinear process that can include many parallel activities. The checklist provided in the following sections is designed to facilitate the T1 EcoRA for a typical site in a site-specific manner. Particular emphasis is placed upon situations typical of the Province, including land uses and characteristic types of ecological structures. As a screening process, the emphasis is on the individual organism. Ecological properties such as population dynamics, species diversity, and production or nutrient cycling are not considered. The document is not intended to provide guidance for wide area and complex sites. These types of sites require specialized expertise and more consultation with BCE.

The organization of the document is linear. This introduction (Section 1) provides an overview of the document and the regulatory framework specific to British Columbia. Section 2 (Problem Formulation) introduces the checklist with the basic collection of information so that a determination of current and future land use can be made. Sections 3 through 7 present specific checklists for the T1 EcoRA for each of several land uses: industrial, commercial, residential, urban park and agricultural, respectively. Each land use is treated independently and the required steps for gathering data for both exposure and effects assessment are listed. The final section of the checklist is Risk Calculation (Section 8). Risk calculation presents the steps for the calculation of risk for both aquatic and terrestrial environments and must be applied to any of the applicable land uses. This section also contains the documentary requirements of BCE.

Appendices provide lists and references for analytical techniques, toxicological and sampling methods, and some additional background on the formulation of a site-specific conceptual model. While the Appendices contain additional biological and toxicological information, they do not replace a good library or other data repositories. Finally, an example risk assessment is presented for a site containing both aquatic and terrestrial components.

1.2 The Basic Framework for Ecological Risk Assessment

The basic framework for ecological risk assessment (EcoRA) has been provided by Environment Canada (1993) and elaborated upon in numerous books (Suter 1993, Landis and Yu 1995). Recent reports have also been published that cover the use of EcoRA for the remediation of contaminated sites (CCME 1996, Environment Canada 1994).

The classical definition of ecological risk assessment is the determination of the probability of an effect occurring to an ecological system.. The critical component of a risk assessment is probability, which estimates the hazard resulting from exposure to a chemical stressor.

A stressor, for the purposes of this document, is a chemical that causes impacts, either positive or negative, upon a biological system. Stressors could be as wide ranging as chemical effects, ionizing radiation, or rapid changes in temperature.

Exposure is the interaction of an organism with a chemical. Exposure often involves measuring the concentrations and persistence of a chemical within the defined ecosystem. In EcoRA it is usual to measure the concentration of the chemical in a particular medium (e.g., water, soil, air). A particular effect resulting from exposure can be estimated based on the environmental concentration (i.e., the concentration of the chemical in a medium) or by the dose of chemical received by the receptor of concern. Whenever possible it is better to measure the dose, which is the amount of chemical gaining entry to the organism of concern, because dose provides a more accurate representation of the potential for toxic effects due to the contamination.

Hazard is the potential of a chemical to cause particular deleterious effects upon a organism or ecosystem. Hazard assumes that exposure has occurred. The determination of an LD50 or the mutagenicity of a material are estimations of the hazard posed by a stressor to a particular receptor.

The receptor is the organism of concern or ecosystem that is being investigated. A receptor could be a specific species of salmon or bird. In some cases like a wide area site, the freshwater benthic community could be the receptor of concern.

A chemical poses no risk to an organism unless exposure occurs. This is extremely crucial as virtually all materials have some biological effect. However, unless enough of the chemical interacts with a biological system, no effects can occur. Risk is a combination of exposure, receptor and hazard expressed as a probability (Figure 1-1). Without overlap between a chemical(s) and a biological entity, there is no risk.

Figure 1-1. The three components of EcoRA

As described in CCME (1996), there are three tiered levels of EcoRA (Figure 1-2). The first level is a screening assessment or Tier 1. In this document a T1 EcoRA is composed of both qualitative and quantitative elements, but the overall process is very straightforward. We expect that 90 percent of the sites within British Columbia can be successfully evaluated using a T1 EcoRA. The Tier 2 EcoRA involves more detailed analysis using techniques such as Monte Carlo analysis and extensive sampling of the site and the resident organisms. Tier 3 EcoRAs address less than 1 percent of contaminated sites, but will typically involve an extensive analysis which can entail a series of unrelated chemical stressors, a wide variety of habitat and terrain types, and a wide geographical area.

Figure 1-2. The tiered approach to EcoRA. T1 EcoRA is expected to be able to cover 90 percent of the sites in British Columbia

1.3 Regulatory Context, or How Did I Get to the Risk Assessment Option?

British Columbia's Contaminated Sites Regulation (BCE, 1996a) provides technical support for the Waste Management Act. The regulations cover, but are not limited to, the following:

Under the Contaminated Sites Regulation, cleaning up a site to meet risk-based standards requires a quantitative human health risk assessment and an environmental impact assessment. The risk management approach to contaminated site remediation can be both scientifically defensible and cost-effective. However, it has limitations that may make its use inappropriate at some sites. Recognizing that risk assessment may not be a useful tool for all sites, guidance is provided on:

1.3.1 Deciding if a site is contaminated

The Contaminated Sites Regulation outlines the general process leading to the decision that a site is contaminated; this process is illustrated in Figure 1-3.

Figure 1-3. General process for managing contaminated sites in BC.

Filling out a site profile, an early part of site assessment, is a qualitative exercise. Suspected contamination based on a site profile can trigger a site investigation, which may consist of two stages:

1.3.2 Remediation options

The overall goal of contaminated site remediation is to restore the environmental quality of the site to a level that does not pose unacceptable risks to humans or ecological resources. The regulations provide the responsible party with a choice of two approaches related to the determination of acceptable cleanup levels (i.e., remediation standards) for contaminated sites:

These are also shown in Figure 1-3.

The numerical standards (generic or matrix) provided in the Contaminated Sites Regulation (BCE, 1996) represent acceptable substance concentrations for various media for various land and water uses. The standards derivation process considered differences in what constitutes acceptable risks for various land and water use designations. The standards are believed to be generally protective of each land and water use. Sites are cleaned up to these standards by removal or treatment of contaminated soil and/or water.

Recognizing that it is not scientifically defensible to have a single numerical standard that protects all sites and site uses in British Columbia (BCE, 1996b), the regulations support the development of site-specific standards and the consideration of local background concentrations. Local physical, biological, or chemical factors may make the application of the generic and matrix numerical standards inappropriate. Site-specific standards consider some of these local factors, and more accurately reflect the conditions at the site. As with the generic and matrix standards, sites are remediated by removal or treatment of contaminants so that the concentrations in soil and water no longer exceed the numerical standards.

The risk-based approach allows contaminants to be managed in place. The capability of a T1 EcoRA to estimate the risks on a site-specific basis is the goal of this checklist.

All the approaches can account for natural elevations in substances, particularly metals, and allow, where appropriate, the use of local background concentrations as remediation standards.

1.3.3 Monitoring a site after cleanup

As shown in Figure 1-3, the use of both the numerical and risk-based standards approaches to cleaning up sites requires site monitoring after remediation is complete. If the numerical standards have been used, the residual soil and water must be checked to ensure that it meets the numerical standards. In cases where the risk-based standards have been used, long-term custom monitoring programs must be adopted, to ensure the effectiveness of risk management works and to assess where applicable the effectiveness of no-action alternatives.

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1.4 What is the Checklist?

The checklist is a step-by-step process that uses a specific protocol to collect the types of data necessary for a T1 EcoRA. The types of data are explained and when multiple management options are possible they are listed in order of preference (i.e., most preferred option is given first).

The process emphasizes using data available from the site rather than extrapolation from complex models. Looking at the site and making observations and measurements is always given the highest priority. Each T1 EcoRA is by definition site-specific, but the checklist provides a common reporting format that should facilitate comparisons between sites.

It is assumed that the T1 EcoRA is being conducted in parallel with the human health risk assessment. At several points in the checklist this overlap is highlighted. Sampling and characterization of the site should be coordinated for the two distinctly different types of risk assessments.

1.5 Use of the Checklist

The overall flow of the T1 EcoRA checklist is portrayed in Figure 1-4. The first step is the performance of the Problem Formulation Checklist (Section 2). This checklist is used to define the type of land use and to gather preliminary information about the site. As the Problem Formulation Checklist is completed, the reader is directed to one of the next five sections, which are specific to the land uses included in the Contaminated Site Regulation (i.e. industrial, commercial, residential, urban park, or agricultural land uses).

The land use specific sections direct the gathering of effect and exposure information that will be used in the final risk calculation. Although each of the sections follows an identical format, there are differences in the rules that determine which species are considered, what toxicity values are used as limits, and what kind of analytical work will have to be accomplished.

The land use specific sections also define typical conceptual models. Conceptual models are the framework of the risk assessment and identify the types of organisms to be considered, potential routes of exposure for these receptors, and delineate the contamination sources at the site. Conceptual models for all contaminants of concern at a site should be completed, recognizing that these models may differ due to differences in the chemical, physical, and environmental fate and transport properties of the contaminants. The generic basis for each type of conceptual model is presented as a graphical figure, and the proper derivation of a site specific conceptual model in presented is Appendix A.

The checklist and accompanying conceptual models are intended to represent the generic conditions anticipated for most contaminated sites. On occasion, site specific consideration and habitat management objectives may require the adjustment of these generic models and receptor assumptions.

As the checklist is followed in the appropriate section, tables of effects and exposure information are generated. By the end of the checklist all of the information necessary for the calculation of risk should have been acquired.

The final section, which like the Problem Formulation is common to all of the risk assessments, is Section 8, Risk Calculation and Reporting,. Detailed instructions on how to estimate risk are included and a variety of options presented in order of preference.

The last part of Section 8 lists the reporting requirements for the T1 EcoRA. If properly followed, the checklist should provide sufficient information for a risk management or clean-up decision. The standardized reporting format should expedite review of the risk assessment by BCE and other interested parties.

Figure 1-4. Flow diagram for the T1 EcoRA checklist.

References:

CCME (1996) A Framework for Ecological Risk Assessment : General Guidance. Winnipeg, Manitoba

Environment Canada (1993) A Framework for Ecological Risk Assessment at Contaminated Sites in Canada. Environment Canada, Hull, Quebec.

Environment Canada (1994) A Framework for Ecological Risk Assessment at Contaminated Sites in Canada: Review and Recommendations. 1994. Scientific Series No. 199. Ottawa.

Landis, W.G. and Yu, M.H. (1995) Introduction to Environmental Toxicology and Chemistry. Lewis Publishers, Boca Raton, FL.

Suter, G.W. (1993) Ecological Risk Assessment. Lewis Publishers, Boca Raton, FL.