Framework for Addressing and Managing Aquatic Contaminated Sites Under the FCSAP

Table of Contents

Executive Summary

Glossary of Terms

List of Acronyms

Tables

Figures

Appendices

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Executive Summary

A common, risk-based framework for the adaptive management of contaminated aquatic sites under federal custody is described. This framework, developed for the Aquatic Sites Working Group subcommittee of the inter-departmental Contaminated Sites Management Working Group (CSMWG), is based on the CSMWG (1999) 10-step process for terrestrial contaminated sites (A Federal Approach to Contaminated Sites).

The framework described herein is also a 10-step process, which begins with Information Gathering (Steps 1-2), during which suspect aquatic sites are identified for further assessment and aquatic sites that are not suspected of being contaminated are eliminated from further consideration. Steps 3-4 involve Screening Level Assessment, during which contaminated aquatic sites are classified as either:

  • Requiring risk management (e.g., remediation);
  • Requiring further assessment; or,
  • Eliminated from further consideration.

Steps 5-6 involve Detailed Level Assessment of sites classified for further assessment, following which these aquatic sites are either prioritized for further management action(s) or eliminated from further consideration. Risk Management strategies are developed and implemented for prioritized contaminated aquatic sites in Steps 7 and 8. Risk Management monitoring (confirmatory sampling and long-term monitoring) is conducted in Steps 9 and 10 to ensure that remedial objectives are met.

The framework is iterative and sequential in both scope and decision points (the latter comprise simple “yes” or “no” criteria). It is intended to be sufficiently prescriptive to standardize the decision-making process while still allowing for necessary site-specific flexibility.

Detailed guidance regarding Steps 1-3 and 5 is provided by the Canada-Ontario Decision-Making Framework for Assessment of Great Lakes Contaminated Sediment (Environment Canada and Ontario Ministry of the Environment 2008, the COA), and in the five appendices. Guidance for completing Steps 4 and 6 is included with the Aquatic Sites Classification System (CSMWG 2009) and detailed guidance for Steps 7-10 is provided in the text, in key references cited in the text, and in Appendix A.

Aquatic sites entering the process can be eliminated from further consideration at three decision points or can be prioritized for management action(s). Contaminated aquatic sites where management action(s) are necessary remain within the process until successful remediation has been achieved and confirmed. Successful remediation is defined as a condition where there are negligible risks to human health or the environment.

Glossary of Terms

Acute toxicity - Toxicity having a sudden onset, lasting a short time and severe enough to induce a rapid response. The duration of an acute aquatic toxicity test is generally on the order of days and mortality is the response typically measured.

Adaptive management - Management approach that: considers uncertainty; involves iterative decision-making (evaluating results and adjusting on the basis of what has been learned); and, emphasizes continual improvement to optimize decision-making.

Adverse effect - An undesirable or harmful effect to an organism, indicated by some result such as mortality, reduced growth, reduced fecundity, behavioural or visible pathological changes.

Aquatic site - A water lot, or land or part of land, completely or occasionally submerged by water. Aquatic sites include freshwater and marine sites, and the hyporheic zone (where shallow groundwater and surface water mix; Boulton et al. 2010), but exclude deep-seated groundwater.

Area use - The extent to which an area is used (e.g., for feeding, rearing) by organisms such as fish.

Assessment endpoint - The explicit expression of the environmental value that is to be protected; the undesired effect whose probability of occurrence is estimated in a risk assessment. Examples include extinction of an endangered species, eutrophication of a lake, or loss of a fishery.

Authorization - Section 35 of the Fisheries Act prohibits the harmful alteration, disruption or destruction of fish habitat, but also provides for terms and conditions which would allow for works or undertakings to proceed in compliance with the Fisheries Act.

Background - An area not influenced by chemicals released from the site under evaluation; conditions prior to contamination (i.e., anthropogenic influences responsible for elevated sediment contaminant concentrations are absent but natural influences are present). Background will vary depending on site-specific conditions. For example, naturally mineralized areas will have elevated background concentrations of metals.

Benthic - Referring to organisms living in, or on, the sediments of aquatic habitats.

Benthos - The sum total of organisms (including plants and animals) living in, or on, the sediments of aquatic habitats.

Bioaccumulation - The accumulation of a substance in the tissues of a living organism via water and food.

Bioaccumulation factor (BAF) - The concentration of a chemical in tissue divided by its concentration in the diet.

Bioassay - The use of an organism or part of an organism as a method for measuring or assessing the presence or biological effects of one or more substances under defined conditions. A bioassay test is used to measure a degree of response (e.g., growth or death) produced by exposure to a physical, chemical or biological variable (a toxicity test) or uptake of a chemical into an organism (a bioaccumulation test).

Bioavailability - Refers to the fraction of the total chemical in the surrounding environment which can be taken up by organisms (US National Research Council 2003). The environment may include water, sediment, suspended particles, and food items.

Bioconcentration - The accumulation of a substance in the tissues of a living organism via water only.

Biomagnification - Uptake of one or more of certain organic contaminants (e.g., methyl mercury, PCBs - not all organic contaminants biomagnify) via dietary uptake through a food chain resulting in increasing concentrations through three or more trophic levels. Inorganic substances such as metals (e.g., inorganic mercury) and metalloids do not biomagnify.

Biota sediment accumulation factor (BSAF) - A parameter describing bioaccumulation of chemicals from sediments into tissues of ecological receptors.

Blank - The measured value obtained when a specific component of a sample is not present.

Chronic toxicity - A biological response of relatively slow progress and long continuance usually associated with lower concentrations of a stressor (e.g., a chemical) than would cause an acute toxicity response.

Concentration - The amount of a substance (e.g., a chemical) in a given environmental medium.

Conceptual site model (CSM) - A diagrammatic representation of a site and its environment that represents what is known or suspected about contaminant sources as well as the physical, chemical and biological processes that affect contaminant transport to potential environmental receptors (Appendix C).

Contaminant - Any physical, chemical, biological or radiological substance in air, soil, sediment or water whose concentration exceeds guideline and/or background concentrations or which is not naturally occurring in the environment.

Contaminant of concern (COC) - A contaminant at a site that adversely affects a human or non-human biological receptor.

Contaminant of potential concern (COPC) - A contaminant at a site that has the potential to adversely affect a human or non-human biological receptor.

Contaminated site - A site at which substances (e.g., chemicals) occur at concentrations above background levels and may pose an immediate or long-term hazard to human health or the environment, or exceed concentrations specified in policies or regulations.

Data quality objectives (DQO) - Qualitative and quantitative statements of the overall level of uncertainty that a decision-maker will accept in results or decisions based on environmental data. DQO provide the statistical framework for planning and managing environmental data operations consistent with user needs (Appendix B).

Ecological risk assessment (ERA) - The process of defining and quantifying risks to non-human biota, i.e., the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. This definition recognizes that a risk does not exist unless: (1) the stressor has an inherent ability to cause adverse effects; and (2) it is coincident with or in contact with the ecological component long enough and at sufficient intensity to elicit the identified adverse effect(s). A screening level assessment (SLA) is less site-specific and thus more uncertain than a detailed level assessment (DLA).

Empirical - Derived from or depending on experience or observation/experimentation rather than theory or logic.

Environmental management plan (EMP) - Outlines the regulatory and permitting requirements specific to the site management / remediation project and identifies the potential environmental effects and how they can be mitigated. It also identifies environmental performance criteria (e.g., turbidity criteria) that should not be exceeded during the work as well as the actions that should be taken in the event that they are exceeded.

Environmental protection plan (EPP) - A project-specific plan that outlines roles and responsibilities of the custodial organization, the contractor's staff, the location of spill response equipment, and the specific measures that they will use to meet environmental protection requirements. Should be consistent with the CEAA EA.

Epifauna - Animals that live on the surface of sediment, rocks, vegetation or other substrates on the bottom of water bodies (e.g., some shrimp-like organisms, some insect larvae).

Expert Support - Technical advice, training and guidance provided by Environment Canada, Health Canada, and Fisheries and Oceans Canada; regionally they assist in determining health and environmental impacts related to contaminated aquatic sites. They establish and maintain links with provincial or territorial governments, review risk assessments and risk scoring of sites to enable the development of government-wide Priority Lists of Projects and assist custodians with the development of remediation, risk-management, and/or care-and-maintenance plans for highest risk sites. Public Works and Government Services Canada also provides Expert Support for the development of project management tools, the dissemination of information on innovative technologies, and industry liaison. For further information, consult the Federal Contaminated Sites Action Plan - Guidance Manual (Jacques Whitford 2008).

Exposure - The contact between a contaminant and a biological receptor (i.e., an individual or population). Even the most toxic material does not pose risk if there is no exposure pathway.

Fish - Fish, shellfish, crustaceans, marine animals and their eggs, sperm, spawn, larvae, spat and juvenile stages (Fisheries Act, Section 1).

Fish habitat - The spawning grounds, nursery, rearing, food supply and migration areas on which fish depend directly or indirectly in order to carry out their life processes (Fisheries Act, Section 34).

Foraging - The act of searching for food and provisions.

Generic - Applicable to a broad range of receptors, site conditions and regions.

Groundwater - All subsurface water that occurs beneath the water table in rocks and geologic formations that are fully saturated.

Guideline - A generic threshold below which adverse effects of contaminants are unlikely to occur and above which adverse effects may occur. Refer to the definition of Sediment Quality Guideline, below.

Habitat compensation- An option when residual impacts of works or undertakings on habitat productive capacity are deemed to still be harmful after relocation, redesign, or mitigation options have been implemented. Compensation for loss of critical habitats should only be considered where full compensation for loss of those habitats is achievable. Compensation is not an option for loss of habitat productive capacity due to the deposition of deleterious substances in any type of habitat.

Hazard - The possibility of an adverse effect, e.g., a measure of the toxic potential of a substance.

Human health risk assessment (HHRA) - The process of defining and quantifying risks to human health: evaluates the likelihood that adverse human health effects may occur or are occurring as a result of exposure to one or more stressors. This definition recognizes that a risk does not exist unless: (1) the stressor has an inherent ability to cause adverse effects; and (2) it is coincident with or in contact with the one or more humans long enough and at sufficient intensity to elicit the identified adverse effect(s).

Hyporheic zone - Where shallow groundwater and surface water mix (Boulton et al. 2010).

Hypotheses- Assumptions made in order to evaluate logical or empirical consequences, or suppositions tentatively accepted to provide a basis for evaluation.

Infauna - Invertebrate organisms living within the bottom sediment of fresh, estuarine or marine waters (e.g., aquatic worms, some insect larvae).

Institutional controls - Non-engineered instruments, such as administrative and legal controls, that help minimize the potential for exposure to contamination and/or protect the integrity of a remedy. They play an important role in site remedies because they reduce exposure to contamination by limiting aquatic site or resource use and guide human behaviour at a site. For instance, zoning restrictions can prevent aquatic site uses such as dock construction, which could affect the integrity of an engineered cap.

Invertebrate - Animal lacking a dorsal column of vertebrae or a notochord.

Letter of Advice - Letter issued, when an Authorization is not required, indicating whether or not there are implications of the proposed work under the Fisheries Act. If there are implications, the letter may contain proactive advice (e.g., information on mitigation measures that would help to minimize effects on fish and fish habitat).

Line of evidence (LOE) - A component of weight of evidence determinations (e.g., toxicity, benthos alteration, biomagnification, chemical contamination).

Measurement endpoint - An expression of an observed or measured response to a hazard; a measurable environmental characteristic that is related to the valued characteristic chosen as the assessment endpoint.

Media - The fundamental components of the aquatic environment including air, water, sediment, soil and biota.

Migration - Movement of substances or biota.

Mitigation - Actions taken to alleviate potential or actual adverse effects to humans or the environment.

Monitoring - Determining changes or trends in measured parameters (e.g., contaminant concentrations in different media, the status of resident populations of biota).

Pathway - The route along which a chemical substance or hazardous material moves in the environment.

Pollution - Contamination resulting in adverse biological effects.

Problem formulation - A preliminary step when initiating a risk assessment, which develops and communicates the risk assessor's understanding of a suspect site. It defines the nature of the contaminants (stressors) involved, the pathway(s) by which these contaminants interact with aquatic organisms, the suite of aquatic organisms that will be considered in the risk assessment, and explicit identification of what needs to be protected and how that will be measured. Equivalent to Data Gathering (Steps 1-2) in this document.

Receptor - The entity (e.g., organism, population, community, ecosystem, humans) that might be adversely affected by contact with or exposure to a substance of concern.

Receptor of concern (ROC) - Human or non-human biota that are exposed to and may be adversely affected by contaminants or other stressors.

Receptor of potential concern (ROPC) - Human or non-human biota that may be exposed to and adversely affected by contaminants or other stressors.

Reference area - An area that is similar to the contaminated site(s) being investigated but which has minimal or low levels of contamination. Identification of a reference area (or site) will depend on: physical, chemical and biological parameters being evaluated; historical and existing conditions; and remedial goals and options. Reference areas serve for comparison to contaminated sites as part of the assessment of potential human or ecological risk.

Remediation - Improvement of a contaminated aquatic site to prevent, minimize or mitigate damage to human health or the environment; an activity undertaken to correct an unacceptable existing condition (e.g., treating or moving polluted sediment). Remediation involves the development and application of a planned approach that removes, destroys, contains, or otherwise reduces the availability of contaminants to receptors of concern.

Residuals - The quantity of material remaining after a process (e.g., the amount of contaminated sediment remaining after remedial activities such as dredging have been undertaken).

Risk - The probability of an adverse effect as measured by exposure of receptors of potential concern to contaminants of potential concern.

Risk assessment (RA) - A scientific examination of the probability that contaminants will adversely affect humans or the environment.

Risk hypotheses - Specific assumptions about potential risk to assessment endpoints; may be based on theory and logic, empirical data, mathematical models, or probability models (Appendix D).

Risk management - Selection and implementation of a strategy to control (e.g., reduce or eliminate) risk followed by monitoring and evaluation of the effectiveness of the chosen strategy; incorporates both scientific (risk assessment) and non-scientific (e.g., social, economic) considerations.

Screening - A rapid analysis to determine if further action (e.g., detailed analysis or remediation) is necessary.

Sediment - Material, such as sand or mud, suspended in or settling to the bottom of a liquid. Sediment input to a body of water comes from natural sources, such as erosion of soils and weathering of rock, or as the result of anthropogenic activities, such as forest or agricultural practices, or construction activities.

Sediment quality guideline (SeQG) - Numerical concentrations or narrative statements that are set with the intent to protect all forms of aquatic life and all aspects of aquatic life cycles during an indefinite period of exposure to substances associated with bed sediments. Adverse effects are expected to occur rarely at levels below an SeQG. At levels above an SeQG, there is an increased probability of an adverse effect. Refer to the definition of Guideline, above.

Site-specific - Specific to a particular site, taking into consideration the site's unique physical, chemical and biological characteristics. A site-specific guideline considers site-specific science-based factors (physical, chemical and biological), while a site-specific objective considers science and/or socio-economic and/or technological factors and/or policy factors (e.g., management goals).

Stressor - Any physical, chemical or biological factor that causes stress to an organism.

Surface water - Water in direct contact with the atmosphere (e.g., rivers, streams, lakes, wetlands, estuaries, artificial water courses such as canals).

Surficial - On the surface.

Tiered assessment - An iterative process in which the initial assessment is the simplest (e.g., minimal site-specific data) and most conservative, and thus will not always provide sufficient certainty for decision-making. The initial assessment will serve to determine three possibilities: (1) no pollution; (2) pollution; (3) there is too much uncertainty for a determination without further investigation. Management decisions can reasonably be made for possibilities 1 and 2 without further assessment. However, possibility 3, which typically will comprise more cases than possibilities 1 and 2, will require further assessment (i.e., further tiers). Successive tiers will involve more focused (e.g., site-specific) investigations, informed and focused based on the results of the previous tier. Data needs are relatively low at the initial tier, but increase at successive tiers; however, uncertainty also reduces at successive tiers. Weight of evidence typically determines the tier at which uncertainty has been reduced sufficiently for informed management decision-making.

Toxicity - Any type of damage, permanent or temporary, to the functioning of a human or non-human organism; the inherent potential or capacity of a substance to cause adverse effects in a living organism. Defined by the Canadian Environmental Protection Act, Part 5, S.64: “have or may have an immediate or long-term harmful effect on the environment or its biological diversity; constitute or may constitute a danger to the environment on which life depends; or constitute or may constitute a danger in Canada to human life or human health.”

Trophic level - Functional classification of organisms in a community according to feeding relationships - e.g., the first trophic level includes green plants, the second level includes herbivores (plant eaters), etc.

Weight of evidence (WOE) - A determination related to possible ecological impacts based on multiple Lines of Evidence.

List of Acronyms

ASWG - Aquatic Sites Working Group

BAF - Bioaccumulation factor

BSAF - Biota sediment accumulation factor

CAD - Confined aquatic disposal

CALA - Canadian Association for Laboratory Accreditation

CCME - Canadian Council of Ministers of the Environment

CDF - Confined disposal facility

CEAA - Canadian Environmental Assessment Act

CEPA - Canadian Environmental Protection Act

COA - The Canada-Ontario Decision-Making Framework (Environment Canada and Ontario Ministry of the Environment 2008; the COA)

COC - Contaminant of concern

COPC - Contaminant of potential concern

CSM - Conceptual site model

CSMWG - Contaminated Sites Management Working Group

DFO - Fisheries and Oceans Canada

DLA - Detailed level assessment

DQO - Data quality objectives

EA - Environmental assessment

EC - Environment Canada

EMP - Environmental management plan

EPP - Environmental protection plan

ERA - Ecological risk assessment

FA - Fisheries Act

FCSAP - Federal Contaminated Sites Action Plan

HHRA - Human health risk assessment

LOE - Line of evidence

MNR - Monitored natural recovery

NAPL - Non-aqueous phase liquids

PEL - Probable efect level

POM - Particulate organic matter

QA/QC - Quality assurance/quality control

RAP - Remedial action plan

ROC - Receptor of concern

ROPC - Receptor of potential concern

SAP - Sampling and analysis plan

SARA - Species at Risk Act

SLA - Screening level assessment

SeQO - Sediment quality objective

SeQG - Sediment quality guideline

TEL - Threshold effect level - equivalent to a SeQO-low

WOE - Weight of evidence

1.0 Introduction

1.1 Background

The inter-departmental Contaminated Sites Management Working Group (CSMWG) coordinates the management of the thousands of contaminated sites on federal lands for which the Canadian federal government has accepted responsibility, and that require attention. The Aquatic Sites Working Group (ASWG) is a subcommittee of the CSMWG, charged with developing guidance for assessing, classifying, and managing federal aquatic sites funded by the Federal Contaminated Sites Action Plan (FCSAP). Aquatic sites are defined as a water lot, or land or part of land, completely or occasionally submerged by water; they include freshwater and marine sites, and the hyporheic zone (where shallow groundwater and surface water mix; Boulton et al. 2010), but exclude deep-seated groundwater.

The CSMWG (1999) established a common, risk-based approach to the management of contaminated sites under federal custody. This approach incorporates a 10-step process that has proven to be an effective management tool for terrestrial contaminated sites, but which does not provide adequate guidance for aquatic contaminated sites. Aquatic sites differ from terrestrial sites in terms of more difficult access, different receptors and food chains, dominated by hydrology, and more limited interaction with aerial sources. The present guidance document was developed to address this need. It is based on the CSMWG (1999) 10-step process with suitable modifications and updates, combining relevant aspects of human health risk assessment (HHRA) and ecological risk assessment (ERA) approaches. It is also based on the weight of evidence (WOE) approach in the Canada-Ontario Decision-Making Framework (Environment Canada and Ontario Ministry of the Environment 2008), the COA, which is being widely used (e.g., in Europe: Choueri et al. 2010) and includes guidance regarding data quality objectives (DQOs: USEPA 2000, 2006) and contaminated sediment management options. Additional relevant and useful guidance documents include Nikl (2006), CCME (2008) and the references provided in Appendix A.

1.2 Purpose

The purpose of this document is to provide an objective, transparent, consistent and scientifically rigorous framework for identifying and addressing contaminated aquatic sites under the FCSAP. This framework is intended to provide the CSMWG with an efficient, consistent and uniform government-wide approach to the adaptive management of contaminated aquatic sites, but is not intended as detailed guidance for conducting a risk assessment or for preparing a risk management strategy. The primary guidance for implementation of the framework is identical to that of the COA (Section 2.1, p 3) - it shall be applied within the context of common sense. In other words, it will not be applied inflexibly.

There are four other guidance “rules” for the use of this Framework (the COA, Section 2.1, p3):

Sediment chemistry data (e.g., sediment quality guidelines [SeQGs]) will not be used alone for remediation decisions except for two cases. The first case involves “simple contamination where adverse biological effects are likely… when the costs of further investigation outweigh the costs of remediation, and there is agreement to act instead of conducting further investigations.” (Wenning et al. 2005). This first case is intended to apply to small sites with a limited number of contaminants present at extremely elevated concentrations (e.g., well above predicted effects levels). The second case involves sites subject to regulatory action.

Accordingly, any remediation decisions will be based primarily on biology, not chemistry since chemical SeQGs are not clean-up numbers by themselves, and need to be used in a risk assessment framework.

LOE (lines of evidence, e.g., laboratory toxicity tests, models) that contradict the results of properly conducted field surveys with appropriate power to detect changes (e.g., Environment Canada 2002) “are clearly incorrect” (Suter 1996) to the extent that other LOE are not indicative of adverse biological effects in the field.

If the impacts of a remedial alternative will “cause more environmental harm than leaving the contaminants in place”, that alternative should not be implemented (USEPA 1998).

Although the basic framework is not expected to change over time, new knowledge is expected to change and improve the tools available for use within the framework. For example, Environment Canada, in collaboration from Fisheries and Oceans Canada, will soon publish FCSAP supplementary guidance for assessing risk to higher-level receptors including birds and mammals (e.g., from sediment ingestion: Heinz et al. 2010).

The best available science should be used in applying the framework. This will require suitable state-of-the-art expertise in the various disciplines comprising the framework.

1.3 Intended Audience

This document is intended for both scientists and non-scientists, specifically for those conducting investigations of contaminated aquatic sites, and for those making decisions based on those investigations.

2.0 Approach for Addressing Contaminated Aquatic Sites

While this guidance document provides useful information for scientists and non-scientists alike, the implementation of this approach requires sound technical expertise and professional judgement. Initial steps provide for the gathering of aquatic site information necessary for effective management decision-making. At some aquatic sites it may not be necessary to complete all of Steps 1-5 before making a final management decision (i.e., aquatic sites that are clearly not contaminated; or aquatic sites that are clearly heavily contaminated and that, with minimal uncertainty, pose an unacceptable toxic risk to humans or the environment; Figure 1). However, for most aquatic sites all of Steps 1-5 will be necessary for final management decision-making.

Each aquatic site will, to some extent, be unique. Thus, generic approaches, techniques and/or prioritizations may have to be adapted site-specifically to properly characterize and, if necessary, manage different aquatic sites. Dual terrestrial-aquatic sites may require application of both the CSMWG (1999) terrestrial framework and the present aquatic framework; the present aquatic framework applies whenever there is an impacted aquatic portion to any contaminated site.

2.1 Overview

The framework follows the 10 steps of CSMWG (1999) organized into problem formulation, screening level assessment (SLA), detailed level assessment (DLA), and risk management including monitoring (Figure 1). Additional detail is provided in the COA as noted below. Although developed specifically for use in the Great Lakes, the technical foundations contained in the latter document have been widely applied. For example, the Province of Ontario has adapted that framework for assessing contaminated sediments province-wide (Fletcher et al. 2008) and found it to be a useful tool, although Welsh et al. (2009) recommend that the following additional future guidance be developed: minimum data requirements for each line of evidence (LOE); the use and application of best professional judgement (e.g., Bay et al. 2007); appropriate consideration of foraging (i.e., feeding) areas for mobile organisms relative to risks within their foraging areas; and, possible human health risks related to incidental sediment ingestion while swimming/wading and to exposure resulting from the use of contaminated sediments to amend gardens.

Although such additional guidance would be useful and should be incorporated when available, the COA is presently suitable for and should be used for assessing contaminated aquatic sites under the FCSAP as an integral part of Steps 1-5, below. The recommendations of Welsh et al. (2009) as noted above should be considered by the technical professionals implementing the approach. LOE for determining whether aquatic sites are suspect or contaminated under that decision-making framework, and for subsequent risk management and monitoring, fall into three general categories: assessing direct exposure or effects in the water column; assessing direct exposure or effects in the sediments; and assessing indirect exposure and effects through contaminant transfer - in particular through biomagnification - which may affect higher trophic levels including humans. As with the COA, the present document is primarily focused on ecological risk and does not address situations where potential human health concerns are associated with dermal contact to contaminated sediment (e.g., swimming, wading), or by other exposure routes (e.g., flooding resulting in aquatic sediments contaminating residential soils or gardens). Nor does it address the issue of unacceptable levels of contaminants that do not biomagnify, such as Cd, Pb, PAHs, in fish or shellfish. In such situations, a screening level HHRA should be considered to assess potential risks and inform the public.

As noted by Jaagumagi and Persaud (1996) “Due to the complexity involved in evaluating contaminated sediment, it is essential that scientists with strong expertise in sediment chemistry (chemical fate, transport and speciation), sediment toxicity testing, benthic community assessment, food chain effects and environmental statistics assist stakeholder groups in the interpretation of the data. This is especially important in determining differences or effects of sediment contamination compared to reference conditions.”

Useful documents specific to each of the 10-steps shown in Figure 1, and available on-line, are listed in Appendix A. An overview of the 10-step approach is outlined below:

Information Gathering:

The following two steps correspond to initial Screening as specified under Step 1 and the initial part of Step 2 of the COA (pp 7-8):

Step1: Identification of Suspect Aquatic Sites - Aquatic sites suspected of being contaminated are identified based on past or current activities related to the site, including a preliminary review of readily available historical information. Suspect aquatic sites are identified for further assessment and sites identified at this step as not contaminated are eliminated from further consideration; and,

Step 2: Historical Review - All available and relevant historical information pertaining to the suspect aquatic site is assembled and reviewed in detail. This step, corresponding to a Phase I Environmental Site Assessment, comprises a desk-top exercise together with a site visit, whereas Steps 3 and 5 involve intrusive sampling. An initial conceptual site model (CSM; Appendix C) is developed along with a sampling and analysis plan (SAP), which should be reviewed by stakeholders and, where appropriate, also by Aboriginal peoples.

Screening Level Assessment (SLA):

The following two steps correspond to final Screening and Preliminary Quantitative Assessment as specified under the latter part of Step 2 and all of Step 3 of the COA; Steps 4 and 5 of the COA can be considered as part of the information used for site classification (COA, pp 7-18 [Appendix E for Decision Matrix shown on pp 16-17 of that publication]):

Step 3: Initial Testing Program - The SAP is implemented, and provides information additional to that contained in the Historical Review (Step 2, above) to characterize the suspect aquatic site in terms of contaminants of potential concern (COPCs) and receptors of potential concern (ROPCs). The CSM is updated based on these findings. This information, which is equivalent to a Phase II Environmental Site Assessment, is used together with Expert Support (i.e., from Environment Canada, Health Canada, and Fisheries and Oceans Canada) to conduct a preliminary identification of contaminated aquatic sites and of aquatic sites believed not to be contaminated; and,

Figure 1: Steps for Addressing and Managing Contaminated Aquatic Sites

Source: Golder Associates Ltd. As shown, not all steps are required nor do all steps have to be completed in sequence.

Figure 1: Steps for Addressing and Managing Contaminated Aquatic Sites
Text version of Figure 1

In the FCSAP, aquatic sites under federal custody are addressed and managed according to a 10-step approach. The management of these sites begins with an information gathering phase where suspected contaminated aquatic sites are identified (Step 1) and a historical review is conducted (Step 2). During Step 1, if the aquatic site is not suspect, no management actions are needed. However, if the aquatic site is suspect, it is listed on the Federal Contaminated Sites Inventory and a historical review (Step 2) is conducted. Following Step 2, if the aquatic site is no longer suspect, no management actions are needed. If the site is suspected to be contaminated, a screening level assessment is conducted where an initial testing program is developed and implemented (Step 3) and the aquatic site is classified (Step 4). If after Step 3 or 4 the aquatic site is determined not contaminated, no management actions are needed. (It should be noted here that while contaminated sites generally proceed to Step 5 at this point, some contaminated sites classified as Class 1 go directly from Step 4 to Step 7.) If after Step 3 or 4 the aquatic site is contaminated, a detailed level assessment is conducted where a detailed testing program is developed and implemented (Step 5); the aquatic site is then reclassified (Step 6). If after Step 5 or 6 the aquatic site is no longer determined to be contaminated, no management actions are needed. If the aquatic site is determined to be contaminated, the final phase involves risk management of these sites. A risk management strategy is developed (Step 7) and implemented (Step 8; this may include remediation). Confirmatory sampling (Step 9) and long-term monitoring (Step 10) then occurs to confirm that the management and remediation objectives have been met. If the remedial goals have not been met, go back to Step 7 where the risk management strategy was developed, and proceed through the subsequent steps until the remedial goals have been met. Once met, the contaminated aquatic site has been addressed and managed. It should be noted that not all steps are required nor do all steps have to be completed in sequence.

Step 4: Classify Contaminated Site - Based on information contained in Steps 1-3, above, the suspect aquatic site is classified using the FCSAP Aquatic Sites Classification System (CSMWG 2009) and prioritized for either further investigations (i.e., DLA - Step 5, below), risk management actions, or is eliminated from further consideration under FCSAP.

Detailed Level Assessment (DLA):

The following two steps are equivalent to Detailed Quantitative Assessment as specified under Step 6, and assessment of deeper sediments if necessary as specified under Step 7 of the COA (pp 20-22):

Step 5: Detailed Testing Program - Detailed testing is conducted based on the previous steps to reduce uncertainties and allow for informed decision-making regarding the need for remediation/risk management actions. The CSM is updated based on these findings. This information, which is equivalent to a Phase III Environmental Site Assessment, is used together with Expert Support (i.e., from Environment Canada, Health Canada, and Fisheries and Oceans Canada) to conduct a further preliminary identification of contaminated aquatic sites and of aquatic sites believed not to be contaminated; and,

Step 6: Reclassify Contaminated Site - The aquatic site classification in Step 4 is revisited and updated based on the findings of Step 5, above, using the FCSAP Aquatic Sites Classification System (CSMWG 2009). Aquatic sites are either prioritized for management action(s) or eliminated from further consideration.

The above steps comprise a tiered approach to determining whether suspect aquatic sites are contaminated and, if so, whether they require risk management and subsequent monitoring (below). Uncertainty is highest initially (i.e., during problem formulation) and is lowest following Detailed Level Risk Assessment; however, data needs and thus costs increase when going from Step 1 to Step 6 (Figure 2).

Figure 2: Tiered Approach To Risk Assessment (Steps 1-6)

Source: Golder Associates Ltd. (Information Gathering = Steps 1-2; Screening Level Assessment = Steps 3-4; Detailed Level Assessment = Steps 5-6)

Figure 2: Tiered Approach To Risk Assessment (Steps 1-6)
Text version of Figure 2

Figure 2: Steps 1-6 in the 10-step approach to addressing and managing contaminated aquatic sites comprises a tiered approach to risk assessment. Proceeding from Information Gathering (Steps 1-2) to the Screening Level Assessment (Steps 3-4) to the Detailed Level Assessment (Steps 5-6), the degree of uncertainty decreases while the data needs increase.

Risk Management (Strategy):

Step 7: Develop Risk Management Strategy - A site-specific plan, usually including remediation, is developed based on information generated in the previous Steps including risk assessment as an approach to develop remediation objectives; and,

Step 8: Implement Risk Management Strategy - The site-specific plan developed in Step 7 is implemented.

Risk Management (Monitoring):

Step 9: Confirmatory Sampling - Appropriate sampling and analyses are conducted to verify and document the immediate success of the risk management strategy devised in Step 7 and implemented in Step 8. Additional risk management actions may be required dependant on the findings of this sampling (e.g., to deal with dredging residuals, which may involve revisiting Step 7 or earlier steps); and,

Step 10: Long-Term Monitoring - Appropriate sampling and analyses are conducted to verify and document the long-term success of the risk management strategy devised in Step 7, implemented in Step 8 and assessed in Step 9. Additional risk management actions may be required dependant on the findings of this long-term monitoring (e.g., revisiting Step 7 or earlier steps). However, if the long-term monitoring indicates that remedial goals will be met into the foreseeable future, monitoring can be terminated and the contaminated aquatic site can be declared successfully remediated.

The steps outlined above are described in further detail below.

2.2 Information Gathering

Information gathering steps are illustrated in Figure 3, below. Step 3 is the Initial Testing Program.

Figure 3: Steps 1-2 for Addressing and Managing Contaminated Aquatic Sites
Figure 3: Steps 1-2 for Addressing and Managing Contaminated Aquatic Sites
Text version of Figure 3

The information gathering phase contains the first 2 steps in the 10-step approach to addressing and managing contaminated aquatic sites. In Step 1, suspected contaminated aquatic sites are identified. After Step 1, if the aquatic site is not suspect, no management actions are needed. However, if the aquatic site is suspect, it is listed on the Federal Contaminated Sites Inventory and a historical review (Step 2) is conducted. Following Step 2, if the aquatic site is no longer suspect, no management actions are needed. If the site is suspected to be contaminated, proceed to the subsequent step.

2.2.1 Step 1: Identify Suspect Aquatic Sites

Rationale: Make use of readily available information to identify suspect aquatic sites for further investigation and screen out aquatic sites that, with a reasonable level of certainty, are not contaminated to levels of potential concern. Where there is insufficient information to make a determination, further investigation (Step 2) is required.

Aquatic contaminated sites are typically adjacent to active or historical commercial, industrial or waste disposal activities and have received or are receiving contaminants via direct discharges, leaks or spills. They can also be downstream of immediate sources of contaminants to the aquatic environment (e.g., a downstream depositional area). Hydrological factors that govern sediment movement within a watershed (e.g., flow rates, channel morphology, gradient, and stream order) should be considered. Identification of suspect aquatic sites can be based on factors including, but not necessarily restricted to: location (e.g., past or current activities at or near the aquatic site) as noted above; historical and present environmental or other records (e.g., newspaper records of beach closures, fish kills, fishing restrictions); complaints by citizens (e.g., olfactory or visual evidence of contamination in the waters overlying the sediments); information from local anglers (e.g., fish absent from certain areas, fish tumours or deformities); or, property transfer/divestment arrangements that may initiate site investigations as part of a business due diligence initiative.

This step serves to screen aquatic sites into two categories:

  1. Aquatic sites that do not represent a potential risk to human health or the environment (e.g., sites with no evident or suspected contamination above background or reference levels); and,
  2. Aquatic sites that may represent a potential risk to human health or the environment (e.g., sites with evidence of contamination above background or reference levels, or for which insufficient information is available to make a final determination).

Aquatic sites that fall under category ‘a' do not require further investigation. Aquatic sites that fall under category ‘b', which should be placed on the Federal Contaminated Sites Inventory, require further investigation. Such investigation begins with a Historical Review (Step 2, Section 2.2.2, below).

2.2.2 Step 2: Historical Review

Rationale: Make use of historic information to appropriately guide subsequent sampling and analysis (i.e., new data collection), and to avoid generating new data where data already exist.

As much available historical and current information pertaining to the suspect aquatic site as possible should be assembled and reviewed. The review of available information should include, but not necessarily be restricted to: available reports; aerial photographs; regulatory agency records (e.g., Letters of Advice or Authorizations, inspections, Inspector's Directions, provincial or other discharge permits, spill reports, enforcement actions, any habitat compensation or restoration at the site or in the immediate area); information from adjacent industrial or other sources including environmental reports and company records. In addition, a site visit should be conducted and, if possible and appropriate, informed individuals (e.g., local residents, former or retired employees of adjacent facilities) should be interviewed. Federal regulatory agencies (Fisheries and Oceans Canada (DFO) and Environment Canada) and provincial regulatory agencies should be consulted at this step and should be appropriately involved in subsequent steps. A site history should be compiled from the above information. The site history will characterize the activities and chemicals that were or may have been used, or a list of such chemicals associated with known activities can be compiled from reference sources.

Current or past site uses should also be identified. This information can often be obtained from online databases, information obtained from individuals noted above, or by obtaining traditional ecological knowledge from Aboriginal or non-Aboriginal resource users. With specific reference to aquatic sites, the local resource management agency enforcement staff are likely aware of harvesting activities and areas that are in current or intermittent use.

The Historical Review, together with information from Step 1, will provide information for initial decision-making and, if required, further assessment. Specifically, this Review will serve, where possible, to:

  • Identify contaminants of potential concern (COPCs) and, if possible from available information, their concentrations at the sediment surface (e.g., <10cm) and at depth (e.g., >10cm);
  • Identify possible historic and continuing sources of contamination (e.g., discharge such as storm water or off-site migration);
  • Identify ecological receptors of potential concern (ROPCs) that may be affected by COPCs; e.g., fish species and fish habitat; (SARA (Species at Risk Act)-listed species) or provincially-listed species; commercial, subsistence or recreational fisheries for any species, and other receptors upon which such species might depend);
  • Identify human use of the site (including consumption of biota harvested at or near the site and use of sediments to amend garden soil) and potential human receptors of concern;
  • Determine exposure pathways by which COPCs may reach and thus potentially affect ROPCs;
  • Provide information to determine appropriate assessment endpoints (what is to be protected, e.g., organisms living in the sediments, fish feeding on those organisms), and measures of effects and the level of any effects determined (what is actually measured, e.g., for benthos: species diversity, abundance, dominance; for fish: bioaccumulation and/or biomagnification of contaminants, species diversity and abundance, any tumours or lesions);
  • Determine any human health consumption advisories;
  • Determine physico-chemical site characteristics (e.g., sediment grain size, organic carbon content, factors that could modify contaminant bioavailability), including sediment stability (the latter evaluated in more detail in Step 5);
  • Determine water type (marine, fresh, brackish) and physical dynamics (e.g., deposition, erosion, tidal cycles, wave action, ice scour);
  • Determine if there is mixing of shallow groundwater and surface water within the aquatic site (i.e., the hyporheic zone), the location(s) of such and the ecological use made of that mixing zone;
  • Determine whether the site has a high level of environmental sensitivity (based on habitat, not land use), and whether contamination is only from off-site sources; and,
  • Determine appropriate background / reference sample locations as and if required for further assessment.

The above information is used to construct an initial conceptual site model (CSM - Appendix C; examples are provided in Figure 4 for bioaccumulation, an indicator of exposure, and in Figure 5 for biomagnification). The CSM should include potential sources, and the nature and location of contamination incorporating spatial and temporal information as appropriate. The CSM should also capture indicators of adverse effects compared to reference site(s) such as reduced recruitment, incidence of tumours or lesions, reduced species abundance and richness.

The CSM is used as the basis for determining a Sampling and Analysis Plan (SAP) outlining which samples and tests of which environmental matrices are necessary, together with data quality objectives (DQOs - Appendix B), based on risk hypotheses (Appendix D) for further investigation across the suspect aquatic site or at specific locations within the suspect aquatic site under Step 3 (Section 2.3.1, below).

The SAP should establish appropriate sampling techniques and equipment, sample density, sampling media (e.g., water, sediments, pore water, biota), and analytical parameters (i.e., the COPCs and factors that may modify their bioavailability and toxicity). It should include both “hot spots” and reference areas, and should be directed to reducing uncertainties precluding informed management decision-making. It is important that a sufficient number of samples from both the suspect aquatic site and from reference areas are collected to reduce uncertainties and improve management decision-making. Where field studies are involved, it is unrealistic to expect that an actual “control station” exists; multiple reference sites are needed to aid in defining an unpolluted condition. It is anticipated that CCME will publish a document comprising two components relevant to development of the SAP: a framework to aid in collection of representative and reliable surface water, sediment, and biological data; and, guidance on general and media-specific factors to consider in sampling (Leigh et al. 2009).

Information gathered should consider not only surficial sediments (to about 10 cm depth), which are the initial focus, as this is where the majority of sediment-dwelling organisms live, but also deeper sediments and their contamination level and likelihood of being uncovered or even possibly moved such that they could affect surrounding areas. The status of deeper sediments should be reconsidered as additional information becomes available.

Both the CSM and the SAP should be reviewed by regulatory agencies and opportunity for comment should be provided to other stakeholders and, where appropriate, to Aboriginal peoples prior to moving to Step 3. Revisions to the SAP would be expected based on such review. The CSM should be reviewed and updated following Step 3 (Section 2.3.1) and Step 5 (Section 2.4.1) as more information becomes available and as uncertainties regarding CSM components are reduced.

Figure 4: Example of a Pictoral Conceptual Site Model (CSM) for Bioaccumulation of Sediment Contaminants along a Freshwater Aquatic Food Chain.
Figure 4: Example of a Pictoral Conceptual Site Model (CSM) for Bioaccumulation of Sediment Contaminants along a Freshwater Aquatic Food Chain.

Source Golder Associates Ltd. POM = particulate organic matter.

Text version of Figure 4

The displayed pictoral conceptual site model of a freshwater aquatic food chain contains the following features: quiescent water (e.g., Reach 5D, 6), aquatic vegetation (e.g., Canada waterweed, Eurasian water milfoil, and curly pondweed), and silty sediment. The bioaccumulation of sediment contaminants through several different pathways is detailed. These pathways proceed as follows: (i) sediment organic carbon or particulate organic matter to epifaunal invertebrates to forage fish (e.g., sunfish) to predator fish (e.g., largemouth bass), (ii) sediment organic carbon or particulate organic matter to epifaunal invertebrates to juvenile fish to predator fish (e.g., largemouth bass), (iii) sediment organic carbon or particulate organic matter to epifaunal invertebrates to predator fish (e.g., largemouth bass) and bottom fish (e.g., brown bullhead), (iv) sediment organic carbon to infaunal invertebrates to bottom fish (e.g., brown bullhead), and (v) particulate organic matter to zooplankton/water column invertebrates (cladocerans, epiphytic crustaceans, damselfly nymphs) to juvenile fish to predator fish (e.g., largemouth bass).

Figure 5: Example of a Simplified Diagrammatic Conceptual Site Model (CSM) for Biomagnification of Methyl Hg from Sediment through an Aquatic Food Chain to Fish, Birds, and Humans.
Figure 5: Example of a Simplified Diagrammatic Conceptual Site Model (CSM) for Biomagnification of Methyl Hg from Sediment through an Aquatic Food Chain to Fish, Birds, and Humans.

Source: Golder Associates Ltd.

Text version of Figure 5

The displayed diagrammatic conceptual site model is of an aquatic food chain. It is a simplified example for the biomagnification of methyl mercury from sediment to fish, birds, and humans. The biomagnification occurs through several different pathways, which proceed as follows: (i) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to benthic invertebrates through uptake or ingestion to birds and to fish to humans and birds, all through ingestion, (ii) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to vascular plants to fish to humans and birds through ingestion, (iii) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to fish through uptake to humans and birds through ingestion, (iv) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to plankton/periphyton through uptake to benthic invertebrates to birds and fish to humans and birds, all through ingestion, (v) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to plankton/periphyton to fish to humans and birds through ingestion, and (vi) sediments (mercury or methyl mercury) to surface water (mercury; and vice versa) to plankton/periphyton, which is followed by conversion to elemental mercury and volatized to the atmosphere. Finally, the sediments can be buried or diluted.

2.2.3 Information Gathering Summary

Rationale: Readily available information is used to identify suspect aquatic sites for further investigation and screen out aquatic sites that, with a reasonable level of certainty, are not contaminated to levels of potential concern. Where there is insufficient information to make a determination, further investigation (Step 2) is required including a site visit, compiling and assessing all available and relevant historical information, and the development of both a conceptual site model (CSM) and a sampling and analysis plan (SAP).

The initial two steps of the framework comprise a desk-top exercise to identify suspect aquatic sites for further assessment, and to eliminate from further consideration any sites that can be identified with reasonable certainty as not contaminated. An initial CSM is developed for suspect aquatic sites, as is a SAP (COA, pp 7-8 and 25-26). The SAP is implemented in Step 3 (Section 2.3.1) at suspect aquatic sites to address data gaps identified in the historical information review and to enable an update of the CSM.

The size of aquatic sites evaluated in Step 1 will vary widely. Assessment approaches and remedial strategies should take into account the spatial extent as well as the magnitude of contamination. Identifying the initial scope of an assessment depends to some extent on best professional judgement on the likely spatial bounds of contamination, reflected in the SAP, which are confirmed when the vertical and lateral bounds of that contamination have been delineated. The probability that “hot spots” exist, whether or not they have been captured in the data set and whether or not they are likely to influence the characterization of risk is often addressed on the basis of professional judgment. Where a more rigorous and quantitative analysis of “hot spot” delineation is warranted, some approaches to such evaluation can be found in Gilbert (1987).

It is expected that case studies developed through the use of this framework will provide additional guidance in improving procedures for the identification of suspect aquatic sites. Such additional guidance would assist in classification of aquatic sites, in more clearly defining the scope of the SAP, and in subsequent prioritization of suspect and contaminated aquatic sites. The PF would also benefit from case studies regarding delineation of specific reference conditions for different water bodies and from guidance for selecting appropriate reference area(s) within those water bodies.

2.3 Screening Level Assessment (SLA)

SLA steps are illustrated in Figure 6, below. Next steps are either DLA (Step 5) or Risk Management (Step 7).

Figure 6: SLA: Steps 3-4 for Addressing and Managing Contaminated Aquatic Sites

Figure 6: SLA: Steps 3-4 for Addressing and Managing Contaminated Aquatic Sites

Text version of Figure 6

The screening level assessment phase contains Steps 3 and 4 in the 10-step approach to addressing and managing contaminated aquatic sites. In Step 3, an initial testing program is developed and implemented, while in Step 4, the aquatic site is classified. If after Step 3 or 4 the aquatic site is not suspect, no management actions are needed. However, if the aquatic site is suspected to be contaminated, proceed to the subsequent step.

2.3.1 Step 3: Initial Testing Program

Rationale: Conduct sampling guided by and building upon historic information to provide necessary information to determine whether or not the suspect aquatic site may pose a potential risk to the environment and/or to human health.

The Initial Testing Program will provide additional, necessary information to augment the Historical Review (Step 2, Section 2.2.2, above) and reduce uncertainties such that initial suspect aquatic site classification can be conducted (Step 4, Section 2.3.2, below). It consists of the following components and is intended to produce data that are representative of the suspect aquatic site being investigated:

  • Field and/or laboratory investigation and sampling including appropriate quality assurance/quality control (QA/QC) procedures;
  • Sample analyses by accredited laboratories (e.g., Canadian Association for Laboratory Accreditation) including appropriate QA/QC procedures;
  • Data interpretation and evaluation;
  • CSM refinement based on the above components (e.g., refining the COPCs, ROPCs and the exposure links between them); and,
  • Screening level assessment (SLA) based on the degree, nature (e.g., bioavailability), extent and significance of contamination.

The SLA should provide answers to the following questions to allow for classification in Step 4 (Section 2.3.2):

  1. Is sediment toxicity possible (based on comparison to generic sediment quality guidelines (SeQGs))? This comparison should involve the most recent, relevant CCME SeQGs or, in their absence for specific parameters, the most recent, appropriate provincial/territorial guidelines. However, if no Canadian guidelines are available for a parameter, the most recent guidelines from international jurisdictions (e.g., USEPA) can be used. Where guidelines from another jurisdiction are used, a narrative justification for their use should be provided;
  2. Is biomagnification likely (based on the presence of elevated concentrations of those few organic chemicals that biomagnify)?; and,
  3. Are these or other COPC present at concentrations above reference and/or background concentrations?

A suspect aquatic site is considered contaminated if the answers to questions 1 or 2 are ‘yes', and the answer to question 3 is also ‘yes' - for one or more COPCs. If the answers are ‘no', no further action is required. In other words, the suspect aquatic site is not considered contaminated and can probably be classified ‘N' in Step 4 (Section 2.3.2); however, Step 4 still needs to be conducted.

Specifically, the following comparisons and decisions (Table 1) based on the COA (pp 8-9) are made in this step using Expert Support (i.e., from Environment Canada, Health Canada, and Fisheries and Oceans Canada). Two comparisons are made. The initial comparison is a determination of any exceedances of conservative sediment quality guidelines (i.e., Theshold Effects Level (TEL) or SeQG-low; e.g., CCME Environmental Quality Guidelines) and a determination as to whether or not substances that can biomagnify are present. Where exceedances of the conservative SeQG occur and/or substances that can biomagnify are present, a subsequent comparison is to reference conditions (selection of appropriate reference sites / conditions will require expert judgment). The rationale for this second comparison includes both the fact that inorganic and some organic substances occur naturally and may be naturally enriched in some areas (e.g., naturally mineralized areas, oil seeps), and the fact that reference conditions are not totally pristine. Only if concentrations of COPC including substances that can biomagnify are greater than reference conditions, is there potential risk requiring further assessment. The results of both comparisons are considered as part of the more extensive Initial Site Classification conducted in Step 4 (Section 2.3.2), which also considers other concerns (e.g., unexploded ordnance, non-aqueous phase liquids (NAPL), documented impacts to human health).

Table 1: SLA Comparisons and Decisions
Comparison Decision
All sediment COPC < SeQG-low, and no substances present that can biomagnify No further assessment or remediation required
One or more sediment COPC > SeQG-low, and/or one or more substances present that can biomagnify Potential risk; further assessment required as detailed below
Table 1: SLA Comparisons and Decisions
Comparison Decision
[Concentrations of all sediment COPC > SeQG-low and substances present that can biomagnify] ≤ reference conditions and statistically no different than reference No further assessment or remediation required
[Concentrations of one or more sediment COPC > SeQG-low and/or one or more substances present that can biomagnify] > reference conditions and statistically higher than reference Potential risk; further assessment required

2.3.2 Step 4: Initial Site Classification

Rationale: A uniform approach is used to determine whether suspect aquatic sites are in fact contaminated aquatic sites. Sites that are determined not to be contaminated are not a priority for further action. Those that are contaminated but for which there is uncertainty as to whether or not they pose a risk to human health or the environment, will require further assessment (Step 5) before an updated classification is determined (Step 6); those that pose a risk to human health or the environment will typically require further assessment to develop a Risk Management Strategy (Step 7).

This step serves to initially screen aquatic sites determined to be contaminated into one of five classes outlined below for the FCSAP Aquatic Sites Classification System (CSMWG 2009):

The FCSAP Aquatic Sites Classification System (CSMWG 2009) was developed to aid in evaluating the level of concern for aquatic contaminated sites. It provides a uniform approach to classifying such sites by providing a tool designed to screen a contaminated aquatic site with respect to the need for further action (risk management or further investigation) to protect human health and the environment, and considers physical impacts and other [non-chemical] disturbances.

The FCSAP Aquatic Sites Classification System (CSMWG 2009) includes a pre-screening checklist, a site description page, a summary score sheet, and three worksheet pages for the user to complete. Completeness of information for classification is determined and assigned a letter grade (from A to F). Then a contaminated aquatic site is assigned to one of the following five classes:

  • Class 1 - High Priority for Action: The available information indicates that action (further site characterization or risk management) is required to address existing concerns. Typically, Class 1 contaminated aquatic sites indicate high concern for several factors, and measured or observed impacts have been documented. Depending on site-specific information, Step 5 (adequate certainty regarding sources or causation is lacking) or Step 7 (certainty is adequate for management decision-making) would be initiated for these contaminated aquatic sites;
  • Class 2 - Medium Priority for Action: The available information indicates that there is potential for adverse impacts, although the threat to human health and the environment is generally not imminent. Additional investigative work may be carried out to confirm the site classification, and some form of action may be required.
  • Class 3 - Low Priority for Action: The available information indicates that these contaminated aquatic sites are currently not a high concern. However, additional investigative work may be carried out to confirm the site classification, and some form of action may be required. Contaminated aquatic sites classified under Class 3 may or may not be further assessed under Step 5 depending on available resources; they are clearly not the contaminated aquatic sites of highest potential concern;
  • Class N - Not a Priority for Action: The available information indicates that there is probably no significant environmental impact or human health threats. There is likely no need for action unless new information becomes available indicating greater concerns, in which case the aquatic site should be re-examined. Note that Class N sites can exceed CCME or other guidelines if there is no chemical bioavailability resulting in toxicity or there are no receptors or pathways from chemical contaminants to receptors.
  • Class INS - Insufficient Information: There is insufficient information to classify these contaminated aquatic sites. In this instance, additional information is required to address data gaps. Step 5 would be initiated dependant on available resources and other priorities.

2.3.3 SLA Summary

Rationale: Sampling, guided by and building upon historic information, is conducted to provide necessary information to determine whether or not the suspect aquatic site may pose a potential risk to the environment and/or to human health. This information is used to classify aquatic sites as: not contaminated and thus not requiring further investigation; contaminated and requiring risk management and probably treatment (Step 7); and too uncertain to classify without further investigation (Step 5) and an updated classification (Step 6).

The third and fourth steps of the framework comprise initial testing of suspect aquatic sites followed by initial classification. Suspect aquatic sites are then either identified as contaminated aquatic sites or eliminated from further consideration. Contaminated aquatic sites are prioritized for either further investigations or management actions.

Initial testing (Step 3) is conducted as outlined in the COA (pp 11-14). However, the SLA would benefit from additional future guidance (i.e., based on directed research and/or case studies) regarding different water bodies: lotic and lentic freshwaters; estuarine waters; and, marine waters.

2.4 Detailed Level Assessment (DLA)

DLA steps are illustrated in Figure 7, below (COA; pp 20-22). A determination that an aquatic site is contaminated (Step 6) results in risk management (Steps 7 and 8) and subsequent confirmatory sampling and monitoring (Steps 9 and 10) for that aquatic site.

Figure 7: DLA: Steps 5-6 for Addressing and Managing Contaminated Aquatic Sites
Figure 7: DLA: Steps 5-6 for Addressing and Managing Contaminated Aquatic Sites
Text version

The detailed level assessment phase contains Steps 5 and 6 in the 10-step approach to addressing and managing contaminated aquatic sites. In Step 5, a detailed testing program is developed and implemented, while in Step 6, the aquatic site is reclassified.

2.4.1 Step 5: Detailed Testing Program

Rationale: Aquatic sites that have initially been determined as contaminated in Step 4, but for which additional information is required before they can be confirmed as contaminated aquatic sites and appropriate Risk Management Strategies developed (Step 7), are further assessed. The results of these assessments and the above comparisons are considered as part of the more extensive Site Reclassification conducted in Step 6 (Section 2.4.2), below.

The Detailed Testing Program is, effectively, a detailed level assessment (DLA). It is applied, on a high priority basis, to those contaminated aquatic sites classed as Class 1 in Step 4 that will be subject to management actions, but for which further information is required before specific management actions can be determined (e.g., causation for measured or observed impacts remains to be determined). The DLA may also be applied on a prioritized basis, to contaminated aquatic sites classed as 2 and INS in Step 4 (Section 2.3.2) above.

This step further defines the nature of the aquatic site contamination and measured/observed or suspected impacts to allow for re-classification in Step 6 (Section 2.4.2). The Detailed Testing Program generally will focus only on those areas of concern identified in the Initial Testing Program (Step 3, Section 2.3.1). Specific objectives of this step are to:

  • Address key information gaps and data deficiencies identified in Step 3, the Initial Testing Program (i.e., reduce identified uncertainties). For instance, while a smaller suite of chemicals may be analyzed than in Step 3, a greater number of samples are usually collected to quantify the extent of contamination. Natural background levels may also be better defined;
  • Refine the CSM;
  • Provide information necessary to provide an updated site classification (Step 6); and,
  • Provide information necessary to develop a Remediation Plan (Step 7), if required, including input to specifications and tender documents.

The data collected during the Detailed Testing Program should be sufficiently representative of the contaminated aquatic site conditions to refine the CSM and to provide adequate information for site management decision-making. The Detailed Testing Program consists of the following components and is intended to produce data that are reliable and representative of the contaminated aquatic site being investigated:

  • Field and/or laboratory investigation and sampling including appropriate quality assurance/quality control (QA/QC) procedures;
  • Sample analyses by accredited laboratories (e.g., CALA) including appropriate QA/QC procedures; and,
  • Data interpretation and evaluation.

A DLA differs from an SLA in that the measures used will often include biological testing (e.g., toxicity tests or tissue sampling) or ecological community data (e.g., benthic macroinvertebrates, quantitative plant community surveys, etc.), whereas an SLA will be limited to comparisons with established environmental quality guidelines. As discussed further in Section 2.5.1, more emphasis should be placed upon biological/ecological methods as these have greater relevance to resource management policy (DFO 1987) and thus site management objectives.

The outputs of the above components should be used to refine the CSM by re-examining, in light of the more informative data expected from a DLA, the COPCs, ROPCs and the exposure links between them. The scope of a DLA should be based on the SLA and will be dictated by the degree, nature (e.g.,bioavailability), extent and significance of contamination.

The DLA should answer the following question to allow for final classification in Step 6 (Section 2.4.2):

  • Does the contaminated aquatic site pose an unacceptable human or ecological risk such that management action is required?

In a DLA, the specifics of the site under study will, to a greater extent than in an SLA, dictate what information is needed to answer this question. A defensible CSM provides the necessary understanding of the site for a reliable answer. The horizontal and vertical extent of sediment contamination and associated human or ecological risks need to be adequately addressed as a starting point and both surficial sediments (about 10 cm depth) and deeper sediments assessed if exposure to deeper sediments could occur in future due to natural (e.g., a 100-year flood) or anthropogenic factors (e.g., dredging, construction, anchoring). The possibility of contaminant migration via groundwater inputs (i.e., via the hyporheic zone) and/or from surface water bodies or sediments to groundwater during periods of groundwater recharge (e.g., a dry summer) also needs to be addressed. The answer to the above question and the information gathered in this and previous steps should provide a sound basis not only for decisions as to whether or not management actions are required, but also the form that such management actions should take.

The following comparisons and decisions (Table 2) based on the COA (pp 12-14) are made in this step with input from Expert Support (i.e., from Environment Canada, Health Canada, and Fisheries and Oceans Canada), including development of a Decision Matrix for WOE evaluation, as detailed in pages 14-18 of that document and exampled in Appendix E. Human health risks associated with direct contact with contaminated sediments and/or surface water also need to be considered.

Sediment toxicity testing should be applied, using professional judgment, to contaminated sites containing both organic and inorganic contaminants. Bioavailability and toxicity cannot be reliably predicted for either type of contaminant solely based on chemical measurements (Hamers et al. 2010); for example, site-specific conditions will determine whether or not organic contaminants are bioavailable and toxic (Cui et al. 2010; McDonough et al. 2010).

Table 2: DLA Comparisons and Decisions
Comparison Decision
There is no potential for contaminant biomagnification from the sediments through aquatic food chains No further assessment or remediation required relative to biomagnifications
There is potential for contaminant biomagnification from the sediments through aquatic food chains Potential risk; further assessment of biomagnification potential required
Table 2a: DLA Comparisons and Decisions
Comparison1 Decision
All sediment toxicity endpoints < 20% difference from reference No further assessment required relative to laboratory toxicity
One or more sediment endpoints ≥ 20% difference from reference and statistically significantly different than reference Potential risk; further assessment required
Table 2b: DLA Comparisons and Decisions
Comparison Decision
Benthic community assessments appropriate/possible? Yes; conduct such assessments (the COA; pp 13-14) and evaluate the results
Benthic community assessments not appropriate/possible? Do not conduct or include benthic community assessments in the WOE evaluation
Table 2c: DLA Comparisons and Decisions
Comparison Decision
Levels of COPC in deeper sediments below SeQG-low and no substances present that can biomagnify, or deeper sediments very unlikely to be uncovered under any reasonably possible set of circumstances No further assessment or remediation required; management options for polluted surficial sediments should be determined
Levels of COPC in deeper sediments above SeQG-low and/or one or more substances present that can biomagnify, and these sediments may be uncovered under one or more reasonably possible set of circumstances Potential risk; further assessment may be required

1 Note two key differences from the COA (p 13): the first comparison does not include the term “not statistically significantly different than reference” and is less than not less than or equal to 20%; the second comparison is greater than or equal to 20%, not just greater than. Note also that the possibility of future toxicity (e.g., from deep groundwater emerging) needs to be considered.

2.4.2 Step 6: Site Reclassification

Rationale: New information developed in Step 5 is applied to the uniform approach used initially in Step 4 to classify aquatic sites as contaminated or not contaminated. Contaminated aquatic sites will require a Risk Management Strategy (Step 7).

This step repeats Step 4 (Section 2.3.2) using new information generated in Step 5 (Section 2.4.1), above. The FCSAP Aquatic Sites Classification System (CSMWG 2009) is again applied and the contaminated aquatic sites reclassified, or initial classifications are confirmed. There should be no sites classified as INS; sufficient information should now have been generated to adequately classify and prioritize all of the contaminated aquatic sites.

2.4.3 DLA Summary

Rationale: Aquatic sites that could not be classified in Step 4 without further information are subject to further investigations to obtain this necessary information (Step 5), after which a final classification is derived (Step 6).

The fifth and sixth steps of the framework comprise detailed testing of contaminated aquatic sites followed by reclassification. Contaminated aquatic sites are then either prioritized for management action(s) or eliminated from further consideration.

Detailed testing (Step 5) is conducted as outlined in the COA (pp 19-22). However, although that document can be used generically for fresh and marine waters, it specifically applies to fresh waters. The DLA would benefit from more specific guidance regarding estuarine and marine waters (e.g., Choueri et al. 2010).

2.5 Risk Management

Risk management steps are illustrated in Figure 8. The following 11 risk management principles based on USEPA (2002a) should be followed:

  1. Control sources early;
  2. Involve the community early and often;
  3. Coordinate with provinces, territories, local governments, and Aboriginal peoples;
  4. Develop and refine a CSM that considers sediment stability;
  5. Use an iterative approach in a risk-based framework;
  6. Carefully evaluate the assumptions and uncertainties associated with the site characterization data and site models;
  7. Select site-specific, project-specific, and sediment-specific risk management approaches that will achieve risk-based goals;
  8. Use sediment cleanup levels that are clearly tied to risk management goals;
  9. Maximise the effectiveness of institutional controls and recognize their limitations;
  10. Design remedies to minimize short-term risks while achieving long-term protection; and,
  11. Monitor appropriate media (water, sediment, tissue) during and after source control and/or sediment remediation to assess and document remedy effectiveness.

Sparrevik and Breedveld (2009) describe the Norwegian approach for sediment management decisions based on site-specific risk assessment. Note that remediation of some aquatic contaminated sites can be complex. For example, in some cases in order to evaluate the feasibility of certain remedial options, specialized site-specific geotechnical and/or bench-scale testing may be required.

Figure 8: Risk Management Strategy (Steps 7-8) and Monitoring (Steps 7-10) for Addressing and Managing Contaminated Aquatic Sites

These steps follow from the SLA and DLA.

Figure 8: Risk Management Strategy (Steps 7-8) and Monitoring (Steps 7-10) for Addressing and Managing Contaminated Aquatic Sites - These steps follow from the SLA and DLA.

Text version of Figure 8

If after Step 5 or 6 the aquatic site is not suspect, no management actions are needed. If the aquatic site is determined to be contaminated, the final phase in the 10-step approach to addressing and managing contaminated aquatic sites involves the risk management of these sites. A risk management strategy is developed (Step 7) and implemented (Step 8; this may include remediation). Confirmatory sampling (Step 9) and long-term monitoring (Step 10) then occurs to confirm that the management and remediation objectives have been met. If the remedial goals have not been met, go back to Step 7 where the risk management strategy was developed, and proceed through the subsequent steps until the remedial goals have been met. Once met, the contaminated aquatic site has been addressed and managed.

2.5.1 Step 7: Develop Risk Management Strategy Including Remediation

Rationale: Information developed as part of the process that classified contaminated aquatic sites is used to assist in developing a site-specific Risk Management Strategy which typically, but not always, includes remediation, and that is then implemented in Step 8.

This step takes the information generated previously to establish a risk management strategy for contaminated aquatic sites that will typically, but not always, involve some form of remediation. The goal is to develop an adaptive environmental site management strategy in which the levels of, and exposure to, bioavailable and toxic contaminants are reduced so that existing or potential risks to humans and the environment are rendered acceptable. Typically sites considered in Step 7 are well-characterized in terms of contaminant distribution, fate and transport, and in terms of human health and environmental risks.

2.5.1.1 Risk Management Considerations

Rationale: Certain components are common to and need to be included / considered in developing risk management strategies, and there are three pre-requisites to remedial planning: determine causation; control on-going sources of contamination; and, ensure that remedial actions do not cause more environmental damage than they remedy.

Risk management involves a combination of one or both of: contaminant removal or reduction; exposure (i.e., links between receptors of concern [ROCs] and contaminants of concern [COCs]) removal or reduction. Key components in any risk management strategy include, but are not necessarily restricted to:

  • Compliance with standards, criteria and guidance;
  • Long-term effectiveness and permanence;
  • Constraints on implementation (e.g., navigation dredging will obviate capping);
  • Capital and operating costs;
  • Opportunities (e.g., future uses);
  • Overall protection of public health and the environment;
  • Risk tolerance (by the public, regulators and the proponent);
  • Community acceptance; and,
  • The risk management strategy needs to be based upon a clear statement of the problem requiring further action and the goals for site management. The effectiveness of any risk management decisions must then be judged against these goals for site management.

There are three additional points that should be viewed as pre-requisites to remedial planning:

  • It is important to determine causation before taking remedial action(s) involving physical works. If causation is not determined, proposed remedies may not be appropriate and risks may not be reduced. Methods for determining causation are outlined in Chapman and Hollert (2006) and the COA (p 18).
  • It is important that on-going sources of contamination are controlled before taking remedial action(s) involving physical works. Remedial actions are usually ecologically invasive and financially expensive. Source removal or control is a pre-requisite to remediation of the aquatic environment so that the disturbance associated with remedial measures will not need to be repeated. In FCSAP, FCSAP R/RM funding is only available for contaminated sites where the activity that caused the contamination took place prior to April 1st, 1998 and where on-going sources of contamination are deactivated.
  • It is important that remedial actions not cause more environmental damage than they remedy. Remedial actions that offer relatively little environmental benefit compared with their associated environmental damage and costs should be avoided.

Depending on the characteristics of the contaminants and the site, remediation may involve only the termination of ongoing sources and then allowing natural recovery processes to remediate the aquatic site. The remainder of the discussion in this section is predicated on sources having been controlled.

2.5.1.2 Aquatic Remediation Considerations

Rationale: Risk management and remediation are based not on generic environmental quality guidelines but rather on site-specific numeric remediation objectives developed by adapting generic guidelines to reflect site-specific conditions and/or based on risk assessment.

Generic environmental quality guidelines alone should generally not guide decision-making because generic guidelines provide no information on bioavailability, toxicity or effects/impacts to humans or the environment (Wenning et al. 2005). They should not be used as pass/fail values, but rather as triggers for further investigation (i.e., during risk assessment problem formulation [Desrosiers et al. 2009]) or, where conservative guidelines are not exceeded, to screen out non-contaminated sites or as a decision point that further remediation is not required. In general, there should be sound biological information that significant impairment of the aquatic ecosystem is resulting from the COPCs at the site or there should be evidence to support the potential for unacceptable human health risks. Remediation based on simple, numeric exceedance of generic environmental quality guidelines could result in more disturbance to aquatic habitats from the remedial decision than is occurring from the COPCs. For this reason, active remediation would usually be based on the outcome of a DLA. An exception would be a relatively small, highly contaminated aquatic site classified as ‘a' (i.e., Class 1) in Step 4 (i.e., a ‘hot spot'), where all stakeholders agree that management/remediation should occur without further investigation (e.g., the costs of remediation are less than those of further investigations and remedial actions will not cause more environmental damage than they remedy).

Other than the above-noted special case, site-specific numeric remediation objectives should be developed to protect both human health and the environment to the same level that generic guidelines are intended to protect human health and the environment. However, as previously noted, site-specific objectives should not be based on generic environmental quality guidelines which, because of their method of derivation, are typically overly conservative (e.g., are based on total chemical concentrations without considering site-specific bioavailability). Such guidelines serve well for SLA (Step 3, Section 2.3.1) where conservative assumptions are acceptable, but are generally not appropriate for risk management purposes as noted above. Rather, site-specific sediment quality guidelines (SeQGs) or objectives (SeQOs) should be developed (where sediment is the component of interest) based on the information generated previously, adapting generic guidelines to reflect site-specific conditions, and/or based on a risk assessment (CCME 2007; Figure 9).

Figure 9: Steps in the Development of a Risk Management Strategy including Remediation (Steps 7 and 8)

Source: Golder Associates Ltd. The assessment conducted in Step 5 is used to develop site-specific, risk-based remediation objectives

Figure 9: Steps in the Development of a Risk Management Strategy including Remediation (Steps 7 and 8)
Text version of Figure 9

There are several steps that occur between developing a risk management and remediation strategy (Step 7) and implementing it (Step 8). When developing the remediation strategy, site-specific guidelines or objectives along with human health and ecological risk assessments are used to establish the remediation objectives, while in developing the risk management strategy, risk management objectives need to be established. The remediation and risk management objectives are then used to develop a site management strategy. This risk management and remediation strategy is then implemented (Step 8).

SeQOs should ideally be based on ERA and HHRA, which incorporate both chemical and biological data (laboratory and field). In other words, they should be based on information generated previously with the proviso that, for ERA, the results of resident benthic community analyses (if such can be conducted) outweigh the results of laboratory toxicity testing if done with sufficient power to detect change (Suter et al. 2002; Chapman 2007; McPherson et al. 2008; the COA; Fletcher et al. 2008).

Once site-specific SeQOs have been established, a risk management strategy can be determined. This strategy will determine what specific action(s) or remedies are required to meet SeQOs (e.g., to reduce or minimize exposure of ROCs to COCs). Appropriate actions or remedies are influenced not only by risk reduction but also by technical, economic, and social needs specific to the contaminated aquatic site and to potentially affected stakeholders and Aboriginal peoples using that site.

In some cases site management may comprise monitoring rather than physical actions (e.g., monitored natural recovery (MNR; Magar et al. 2009)). Some possible management actions are depicted in Figure 10, relative to both cost and site-specific risk reduction; additional information is provided in Table 3. Risk reduction at a contaminated aquatic site can, without proper planning and controls, result in increased risk off-site (e.g., contaminated water leaching from dredged material placed on land and flowing into groundwaters or surface waters). For this reason, an adaptive environmental management plan (Section 2.5.2) should be considered an integral component of any environmental remediation activity.

There are no zero-risk options for managing contaminated sediments. Both monetary cost-benefit analysis and environmental cost-benefit analysis (i.e., comparative risk:risk analysis) should be undertaken to assist in determining the optimum risk management strategy and, where there are a number of contaminated aquatic sites, prioritizing those sites for remediation. Key questions to consider are:

  • What will change as a result of the proposed management action(s)?
  • Will such management action(s) be of overall benefit to human health and the environment?
  • Are the proposed management action(s) the best one(s) to take or are there better alternatives?

Research may be required to assess the applicability and effectiveness of different possible remedial actions at the contaminated aquatic site. Applicable technologies should be reviewed in detail for the selected remedial action(s).

Figure 10: Possible Management Actions for Contaminated Aquatic Sites Following Source Control: Relative Cost and Relative Immediate Site-Specific Risk Reduction

Source: Golder Associates Ltd. (Site-specific plans often combine these options; however, Site-Specific Risk-Reduction may increase risk elsewhere (e.g. dredged material disposal))

Figure 10: Possible Management Actions for Contaminated Aquatic Sites Following Source Control: Relative Cost and Relative Immediate Site-Specific Risk Reduction
Text version of Figure 10

Possible management actions for contaminated sites are displayed in an order where the first action listed offers the least immediate, site-specific risk reduction, along with the lowest cost. The actions listed then progress towards those with the greatest immediate, site-specific risk reduction and the highest cost. The order of the actions is as follows: (i) no action, (ii) monitored natural recovery, (iii) cap (simple or complex), (iv) shallow removal (dredge/excavate and cap), (v) in situ treatment (biological, chemical, immobilization), (vi) confined disposal facility (or contained aquatic disposal), and (vii) full removal (dredging, excavation, treatment, disposal).

Table 3: Possible Management Actions for Contaminated Aquatic Sites: Suitability, Requirements and Implications
Useful references are provided in Appendix A. Monitoring is a required component of all of these possible management actions.
Constraints Monitored Natural Recovery¹ In Situ Treatment Capping Dredging and Disposal²
Suitable for sediment with the following characteristics Low: toxicity; benthic community impact; biomagnification potential; negligible human health risk Acute toxicity; biomagnifying substances; human health risk Acute toxicity; biomagnifying substances; possibility of future sediment disturbance and exposure of contaminated deeper sediments; human health risk
Not suitable for sediment with the following characteristics Acute toxicity, highly biomagnifying substances Unstable bottom conditions; untreatable chemicals; need for rapid removal/isolation; possibility of future sediment disturbance/ exposure of contaminated deeper sediments Unstable bottom conditions; need for rapid removal/isolation [suitable for all sediments]
Requirements Depositional/stable area; sufficiently high depositional rate; low potential for disturbance (i.e., conditions that progressively reduce exposure of ROCs to COCs) Contaminants amenable to treatment within reasonable time frame Relatively level bottom; low energy; short haulage distance for capping material; possible long-term maintenance plan Minimization of sediment turbidity/ losses during removal/ handling; site engineering; disposal facility
Implications Area use may be restricted with potential economic impact; however, no sediment resuspension, loss or disposal issues Use of area may be restricted; treats only surface of sediment deposits; however, no sediment disposal issues Use of area may be restricted with potential economic impact; may affect navigation (altered water depth); short-term impact on aquatic habitat Short-term impact on aquatic habitat and navigation

1 For information on thin-layer capping to enhance natural recovery: Merritt et al. (2010). Monitored natural recovery should be considered for sensitive, unique environments that could be irreversibly damaged by intrusive management actions such as capping (other than possibly thin-layer capping) or dredging,

2 For information on dredging processes and remedy effectiveness: Bridges et al. (2010).

2.5.2 Step 8: Implement Risk Management Strategy Including Remediation

Rationale: The Risk Management Strategy developed in Step 7 is implemented, including a Remedial Action Plan, an Environmental Management Plan, and selection of appropriate contractor(s) for the remedial works.

The risk management strategy developed in Step 7 (Section 2.5.1) is implemented in this step. Depending on the specific contaminated aquatic site, its sensitivity or proximity to sensitive areas, and the complexity of contamination issues, remediation can range from a straightforward remedy implemented over a relatively short time-frame to a complex remedy or combination of remedies implemented over a relatively long time-frame. Comprehensive evaluation of alternatives, careful planning of remediation and controlled yet adaptable implementation (i.e., adaptive management) will facilitate effective, efficient and economical restoration of a contaminated aquatic site.

2.5.2.1 Preparation of a Remedial Action Plan

Rationale: Certain components are common to and need to be included / considered in Remedial Action Plans.

Once a remedial option has been chosen, a Remedial Action Plan (RAP) is prepared with the assistance of Expert Support (e.g., Environment Canada, Health Canada, Fisheries and Oceans Canada, and Public Works and Government Services Canada). The RAP should include a separate worker health and safety plan and contractor tender documents. A qualified contractor is selected and, depending on the level of experience and capabilities of the contracting team, tasked to provide proper documentation, QA/QC, and communication with stakeholders (and with Aboriginal peoples if appropriate) during implementation of the RAP. Where local contractors may not have the background, expertise or experience to successfully conduct highly specialized work elements, these elements should be subcontracted.

The RAP should include:

  • A summary of the findings of previous site investigations (i.e., of Steps 1-6);
  • COCs;
  • ROCs;
  • Identification, quantification and characterization of the sediments to be remediated;
  • A summary of the remedial options evaluated and of the methodology used to select the preferred strategy;
  • A detailed description of the selected remedial option and its application;
  • A detailed Implementation Plan including schedule and associated costs;
  • Control measures to minimize human and environmental risks during application of the remedial option, including worker health and safety;
  • A contingency plan in the event of unexpected events (e.g., fuel oil spills, release of contaminants from the sediments into the water column to levels of potential concern);
  • Identification of the fate of residual contaminants; and,
  • A description of plans for risk management confirmatory sampling (Step 9) and long-term monitoring (Step 10).

Depending upon the complexity and size of the project, an independent technical review of the RAP may be desirable along with input from stakeholders, and from Aboriginal peoples as appropriate. Regulatory agencies should also be consulted regarding regulatory acceptability, the need for further assessments, and regulatory requirements during implementation.

2.5.2.2 Environmental Management Plan

Rationale: Certain components are common to and need to be included / considered in Environmental Management Plans.

An environmental management plan (EMP) should be prepared as part of the remedial planning with the assistance of Expert Support (e.g., Environment Canada, Health Canada, Fisheries and Oceans Canada, and Public Works and Government Services Canada). The EMP outlines the regulatory and permitting requirements specific to the remediation project and identifies the potential environmental effects and how they can be mitigated. The EMP also identifies environmental performance criteria (e.g., turbidity criteria) that should not be exceeded during the work as well as the actions that should be taken in the event that they are exceeded.

Legislative requirements will vary by province. Federal legislative requirements include the:

  • Canadian Environmental Assessment Act (CEAA, which requires that federal departments, agencies and Crown corporations conduct environmental assessments for proposed projects where the federal government is the proponent);
  • Canadian Environmental Protection Act, 1999 (which provides for the regulation of federal works, undertakings, and federal lands and waters, where existing legislation normally administered under provincial statutes does not apply);
  • Migratory Birds Convention Act, 1994 (which protects and conserves migratory birds, and their nests);
  • Fisheries Act (which regulates activities that can harmfully alter, disrupt, or destroy fish or fish habitat and which prohibits the deposit of a deleterious substance);
    • Appropriate documentation is required before undertaking any work in waters containing fish or fish habitat (e.g., Letter of Advice, Authorization under the Fisheries Act subsection 35(2));
    • Physical works can result in the release of deleterious substances (e.g., sediment-laden water, contaminant release during dredging) and these substances need to be controlled at their source during the remedial works;
    • Restriction on the timing of work is one common management tool to minimize potential impacts to fish or fish habitat, and may have significant impacts to the scheduling of work proposed to be carried out at a contaminated aquatic site;
  • Navigable Waters Protection Act (which requires an approval before any work can be conducted on, in, upon, under, through or across a navigable waterway); and,
  • Canada Water Act (which in Part II deals specifically with water quality management and water pollution), where it applies.

There are a number of best management practices (BMP) documents that are available and that would provide some form of guidance for most types of work in and around water (Appendix A). The EMP should identify which of these BMPs applies to the project.

As the contractor prepares to implement the remedial works, they should prepare a specific task analysis document for health, safety and environmental management. With respect to environmental management, many proponents require their contractor to submit a task-specific Environmental Protection Plan (EPP). The EPP is based on the EMP but is specific to the project and outlines roles and responsibilities of the contractor's staff, the location of spill response equipment, the specific measures that they will use to meet the trigger levels in the EMP, etc.

2.5.2.3 Considerations for Contracting

Rationale: Certain components are common to and need to be included / considered when selecting a suitable contractor for any remedial works.

Selection of a suitable contractor for remedial works will involve preparing detailed specifications and tender documents and checking that both the primary contractor and subcontractors are knowledgeable and experienced at using the recommended remediation technology under similar site conditions and have an effective safety and environmental management program. The specification and tender documents should contain:

  • Concise descriptions and specifications outlining each component of the Implementation Plan;
  • A clear statement of the RAP objectives;
  • Pertinent information regarding the contaminated aquatic site including:
    • Extent and volume of materials (COCs; intervention/remediation SeQOs; horizontal and vertical footprint);
    • Site bathymetry/hydrology/hydrogeology; and,
    • Site physical/geotechnical properties (e.g. deposition/scouring; extreme events such as ice thaw/scour, storms, floods; anthropogenic factors such as navigational dredging, propeller wash, future uses);
  • Clearly defined reporting and documentation requirements;
  • Pre-determined methods for verifying volumes of material removed (e.g., bathymetry, volumes shipped by truck, etc.); and,
  • A request for detailed cost information and for unit rates for possible unforeseen additional work.

The bidders should be able to visit the contaminated aquatic site and should be provided with site reports and the opportunity to ask questions/request clarification. Responses to such questions/requests for clarification must be provided equally to all bidders to provide a ‘level playing field'.

Projects where approvals are in place will generally attract more competitive bids. Package prices where a contractor must obtain agency approvals are viewed as being high risk by most contractors and that risk, usually with a premium attached, will be factored into the bids received or will decrease the numbers of bidders and thus the competitive nature of the bidding.

Proposals developed in response to the specification and tender documents should include:

  • A concise description outlining each component of the Implementation Plan;
  • A detailed work schedule;
  • A health, safety and environmental protection plan or outline how that will be developed if awarded the contract;
  • Identification of any proposed feasibility studies including bench scale tests;
  • A site monitoring plan (addressing Steps 9 and 10, below);
  • A QA/QC plan including an organized, comprehensive record-keeping and documentation system;
  • Deliverables such as environmental monitoring reports, confirmation of remediation reports, etc.;
  • A contingency plan; and,
  • Detailed cost information.

It is important to provide the contractor with as much information as possible so that the contractor is well aware of site conditions. Changes in site conditions from those conditions expected as part of the bid process are the source of many contracting claims.

2.5.3 Risk Management Summary

Rationale: A site-specific Risk Management Strategy, which typically includes remediation, is developed for aquatic sites classified as contaminated in Step 7, and then implemented in Step 8.

The seventh and eighth steps of the framework develop and implement a risk management strategy for contaminated aquatic sites prioritized for management action(s). Site-specific considerations and biological analyses form the basis for developing remedial goals at a contaminated aquatic site. Generally, site-specific numeric remediation objectives need to be developed. Implementation of risk management measures should include consideration of the contracting strategy and how the contractor will, on behalf of the proponent agency, manage health, safety, and environmental risks. Risk management activities would benefit from case studies regarding development, application and implementation of site-specific numeric remediation objectives.

2.6 Risk Management and Remediation Monitoring

Monitoring steps are illustrated in Figure 8.

2.6.1 Step 9: Confirmatory Sampling

Rationale: Confirmatory sampling is conducted to ensure that remedial objectives have been met during and immediately following implementation of the RAP.

Confirmatory sampling is required to demonstrate that the contamination risk to humans and the environment is negligible following remediation. In other words, either contamination has been removed (i.e., dredging), or exposure to contamination has been eliminated (e.g., MNR, in situ treatment, capping).

The remediated areas need to be sampled to verify that the remedial objectives have been met (e.g., residuals from dredging activities do not exceed the SeQOs). If remedial objectives have not been met, additional remedial activities followed by confirmatory sampling will be required. Such additional remedial activities may involve a change in remediation technology. When the objectives have been met, remediation activities and resulting site conditions are documented in a report. Information on site conditions following remediation and acceptable confirmatory sampling will form the basis for subsequent Long-Term Monitoring (Step 10, Section 2.6.2).

Confirmatory sampling should preferably, but not necessarily, be conducted by an independent third party qualified to carry out such work, using standardized and consistent sampling methods. Confirmatory sampling consists of the following components:

  • Field sampling and/or laboratory testing including appropriate quality assurance/quality control (QA/QC) procedures;
  • Sample analyses by accredited laboratories (e.g., CALA) including appropriate QA/QC procedures;
  • Data interpretation and evaluation; and,
  • A clear answer to the question “Does the contaminated aquatic site still pose an unacceptable human or ecological risk such that further management action is required?”

The answer to the above question will be based on site-specific guidelines or objectives to ensure that the remediation objectives are met. (Expert Support will be required to provide guidance (e.g., does one exceedance of a guideline equate to non-compliance?). The FCSAP secretariat is currently developing a site closure process that will include a risk reduction indicator tool. The intent of this tool is to assess whether risk at the site has been reduced to an acceptable level through implementation of the remediation or risk management actions on the site.

2.6.2 Step 10: Long-Term Monitoring

Rationale: Long-term monitoring of all remedial works is conducted to verify that the remedial objectives will be met for the foreseeable future; monitoring is terminated when this has been verified.

The US National Research Council (2007) attempted to answer the question whether dredging alone was capable of long-term risk reduction at US Superfund Megasites. Surprisingly, they could not answer this question because they concluded that monitoring was inadequate. They emphasized that environmental monitoring is an integral part of any remedial option, not an “add-on” or optional activity. Long-term monitoring is thus a requirement for all remedial options.

The objective of long-term monitoring is to confirm that remediation activities will continue to meet the remedial goals for the foreseeable future. Generic guidance on monitoring is provided in Michaud (2000); however, monitoring components will be site- and situation-specific in design, frequency and duration (Appendix A). Such monitoring should be adaptive, based on principles outlined in Lindermayer and Likes (2009) to avoid the three major problems hindering monitoring effectiveness: the wrong drivers (e.g., politics rather than good science); poor initial design; and, lack of clarity regarding goals and components. Doing so will not only avoid unnecessary data collection and miscommunication with stakeholders (e.g., “what should be monitored”?), but will also promote the assessment of the long-term effectiveness of remedial action(s).

Assessment and measurement endpoints forming the basis for the long-term monitoring will be site- and situation-specific based on the finalized CSM (Step 5, Section 2.4.1; Appendix C). The long-term monitoring should:

  • Have clear management relevance and necessity (i.e., there is no point to doing monitoring for its own sake);
  • Be transparent (e.g., repeatable, with all data freely available) and technically defensible (e.g., appropriate QA/QC);
  • Be integrative (internally, using measurement endpoints in a WOE assessment; externally, linking individual source monitoring and regional monitoring);
  • Be agreed on a priori by all stakeholders, and by Aboriginal peoples if appropriate; and,
  • Be conducted by qualified professionals.

Other necessary long-term monitoring components include good a priori statistical design, and adaptation as new knowledge becomes available (e.g., iterative revisions while maintaining the integrity of the long-term data record). In addition to comparing the long-term monitoring results with the remedial goals (e.g., site-specific SeQOs), trends in contaminant concentrations and other trends (e.g., changes in site conditions) should be identified. Changes in site conditions could result in an additional ROPC or exposure pathway that must be considered. A steady increase in concentrations of a contaminant over time could be indicative of contaminant migration (e.g., capping or in situ treatment losing their effectiveness over time), or of new contamination from other sources. Guidance for non-compliance with the remedial goals should be prepared.

Long-term monitoring can be terminated when there is a clear ‘no' answer to the question “Will the contaminated aquatic site pose an unacceptable human or ecological risk in the foreseeable future, such that further management action is required?” At this point the contaminated aquatic site can be declared successfully remediated. However, if remedial goals are exceeded, the RAP must be re-evaluated, which may necessitate revisiting Step 7 (Section 2.5.1) and undertaking appropriate contingency measures. Note that guidance regarding the site-closure process, including elements of both Steps 9 and 10, is currently under development by Public Works and Government Services Canada. Further, the FCSAP Secretariat is currently implementing a risk reduction process for risk management that is based on risk assessment.

2.6.3 Monitoring Summary

Rationale: Confirmatory sampling (Step 9) ensures that remedial objectives have been met during and immediately following implementation of the RAP, while long-term monitoring (Step 10) verifies that the remedial objectives will be met for the foreseeable future.

The final two steps of the framework comprise confirmatory sampling to verify and document the immediate success of the previously determined (Step 7) risk management strategy. Additional risk management actions may be required. If not, or following such actions, long-term monitoring is initiated. Such monitoring terminates once it is clear that the contaminated aquatic site has been successfully remediated. Although generic guidance regarding monitoring is available (Appendix A), case studies would provide useful site-specific examples of monitoring components and of when and why the decision was made to terminate monitoring and declare the contaminated aquatic site successfully remediated such that closure had been reached on future liability.

3.0 References

ASTSWMO (Association of State and Territorial Solid Waste Management Officials). 2009. Framework for long-term monitoring of hazardous substances at sediment sites [PDF 775 KB]. The Sediments Focus Group.

Bay S, Berry W, Chapman PM, Fairey R, Gries T, Long E, MacDonald D, Weisberg SB. 2007. Evaluating consistency of best professional judgment in the application of a multiple lines of evidence Sediment Quality Triad. Integr Environ Assess Manage 3: 491-497.

Boulton AJ, Thibault D, Kasahara T, Mutz M, Stanford JA. 2010. Ecology and management of the hyporheic zone: stream-groundwater interactions of running waters and their floodplains. J N Am Benthol Soc 29: 26-40.

Bridges TS, Gustavson KE, Schroeder P, Ells SJ, Hayes D, Nadeau SC, Palermo MR, Patmot C. 2010. Dredging processes and remedy effectiveness: relation to the 4 Rs of environmental dredging. Integr Environ Assess Manage 6: 619-630 (DOI 10.1002/ieam.71).

CCME (Canadian Council of Ministers of the Environment). 1996. A framework for ecological risk assessment: General guidance [PDF 2.40 MB]. Winnipeg (MN), Canada.

CCME. 1997. A framework for ecological risk assessment: Technical appendices [PDF 3.91 MB]. Winnipeg (MN), Canada.

CCME. 2007. Canadian environmental quality guidelines. Winnipeg (MN), Canada.

CCME. 2008. National classification system for contaminated sites, guidance document [PDF 567 KB]. Winnipeg (MN), Canada.

Chapman PM. 2007. Don't disregard the benthos in sediment quality assessments! Mar Pollut Bull 54: 633-635.

Chapman PM, Hollert H. 2006. Should the sediment quality triad become a tetrad, a pentad, or possibly even a hexad? J Soil Sed 6: 4-8.

Choueri RB, Cesar A, Abessa DMS, Torres RJ, Riba I, Pereira CDS, Nascimento MRL, Morais RD, Mozeto AA, DelValls TA. 2010. Harmonized framework for ecological risk assessment of sediments from ports and estuarine zones of North and South Atlantic. Ecotoxicology 19: 678-696.

CSMWG (Contaminated Sites Management Working Group). 1999. A federal approach to contaminated sites. Ottawa (ON), Canada: Dillon Consulting Ltd.

CSMWG. 2009. FCSAP Aquatic sites classification system. Ottawa (ON), Canada.

Cui X, Hunter W, Yang Y, Chen Y, Gan J. 2010. Bioavailability of sorbed phenanthrene and permethrin in sediments to Chironomus tentans. Aquat Toxicol 98: 83-90.

DFO (Fisheries and Oceans). 1987. Policy for the management of fish habitat. Ottawa (ON), Canada: Fish Habitat Management Branch.

Desrosiers M, Babut MP, Pelletier M, Bélanger C, Thibodeau S, Martel L. 2009. Efficiency of sediment quality guidelines for predicting toxicity: the case of the St. Lawrence River. Integr Environ Assess Manage 6: 225-239.

Environment Canada. 2002. Metal mining guidance document for aquatic environmental effects monitoring. Ottawa (ON), Canada.

Environment Canada and Ministère du Développement durable, de l'Environnement et des Parcs du Québec. 2007. Criteria for the assessment of sediment quality in Quebec and application frameworks: prevention, dredging and remediation [PDF 1.13 MB].

Environment Canada and Ontario Ministry of the Environment. 2008. Canada-Ontario decision-making framework for assessment of Great Lakes contaminated sediment [PDF 1.20 MB]. Ottawa (ON), Canada.

Fletcher R, Welsh P, Fletcher T. 2008. Guidelines for identifying, assessing and managing contaminated sediments in Ontario: An integrated approach. Toronto (ON), Canada: Ontario Ministry of Environment.

Gilbert RO. 1987. Statistical methods for environmental pollution monitoring. New York (NY), USA: Van Rostrand Reinhold.

Hamers T, Leonards PEG, Legler J, Vethaak AD, Schipper CA. 2010. Toxicity profiling: an integrated effect-based tool for site-specific sediment quality assessment. Integr Environ Assess Manage 6: 761-773.

Heinz GH, Beyer WN, Hoffman DJ, Audet DJ. 2010. Relating the ability of mallards to ingest high levels of sediment to potential contaminant exposure in waterfowl. Environ Toxicol Chem 29: 1621-1624.

Jaagumagi R, Persaud D. 1996. An integrated approach to the evaluation and management of contaminated sediments. Ontario Ministry of the Environment, Standards Development Branch, Environmental Standards Section, Toronto (ON), Canada.

Jacques Whitford. 2008. Federal contaminated sites action plan (FCSAP) - guidance manual. Gatineau (PQ), Canada.

Leigh K, Suedkamp-Wells K, Fogg A, Henning M, Hall S, Allaway C. 2009. Development of contaminated site characterization guidance for sampling in support of human health and environmental risk assessments within Canada. Poster presented at 30th Annual North American Meeting of the Society of Environmental Toxicology and Chemistry. New Orleans (LA), USA: November 19-23, 2009.

Lindermayer DB, Likes GE. 2009. Adaptive monitoring: A new paradigm for long-term research and monitoring. TREE 24: 482-486.

Magar VS, Chadwick DB, Bridges TS, Fuchsman PS, Conder JM, Dekker TJ, Steevens JA, Gustavson KE, Mills MA. 2009. Technical guide: Monitored natural recovery at contaminated sediment sites. Environmental Technology Security Certification Program Project ER-0622.

McDonough KM, Azzolina NA, Hawthorne SB, Nakles DV, Neuhauser EF. 2010. An evaluation of the ability of chemical measurements to predict polycyclic aromatic hydrocarbon-contaminated sediment toxicity to Hyalella azteca. Environ Toxicol Chem 29: 1545-1550.

McPherson C, Chapman PM, de Bruyn A, Cooper L. 2008. The importance of benthos in weight of evidence (WOE) sediment assessments - a case study. Sci Total Environ 394: 252-264.

Merritt KA, Conder J, Kirtay V, Chadwick DB, Magar V. 2010. A review of thin-layer placement applications to enhance natural recovery of contaminated sediment. Integr Environ Assess Manage 6: 749-760.

Michaud J-R. 2000. Environmental surveillance and monitoring program for dredging and sediment management projects. Montreal (PQ), Canada: Environment Canada.

Michaud J-R. 2009. Useful references for the development of frameworks for addressing, assessment and management of contaminated sediments and dredged materials: frameworks and useful guidance documents and resources at each step. Montreal (PQ), Canada: Environment Canada.

Nikl L. 2006. Guidance for DFO staff on the review of ecological risk assessments at federal contaminated sites. Burnaby (BC), Canada: Golder Associates Ltd.

Sparrevik M, Breedveld GD. 2009. From ecological risk assessments to risk governance: evaluation of the Norwegian management system for contaminated sediments. Integr Environ Assess Manage 6: 240-248.

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US Army Corps of Engineers, Environmental Protection Agency Region 10, Washington Department of Ecology, Washington Department of Natural Resources, Oregon Department of Environmental Quality, Idaho Department of Environmental Quality, National Marine Fisheries Service, US Fish and Wildlife Service. 2006. Sediment evaluation framework for the Pacific Northwest [PDF 2.13 MB]. Interim Final. Seattle (WA), USA.

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Appendix A - Useful On-Line References for the Framework Steps

References to websites without titles of specific documents contain multiple relevant documents which will be added to periodically. Additional references are provided in Michaud (2009)
Reference Data Gathering (Steps 1-2) Screening Level Assessment (Step 3) Detailed Level Assessment (Steps 5) Risk Management (Steps 7-8) Monitoring (Steps 9-10) Comments

Environment Canada and Ontario Ministry of the Environment (2008) Assessment of Great Lakes contaminated sediment [PDF 1.20 MB]

    Primary guidance document. Steps 4 and 6 involve the FCSAP Aquatic Sites Classification System (CSMWG 2009)
US Army Corps of Engineers et al. (2006) Sediment evaluation framework for the Pacific Northwest [PDF 2.13 MB].     Information on sediment sampling, testing techniques, and interpretation
CCME (1996,1997) Ecological risk assessment (ERA): General guidance [PDF 2.40 MB], ERA: Technical appendices [PDF 3.91 MB]     General guidance for conducting risk assessments in Canada
USEPA Contaminated Sediments in Superfund Guidance documents and fact sheets for assessing and remediating contaminated aquatic sediments
Environment Canada and Ministère du Développement durable, de l’Environnement et des Parcs du Québec (2007) Sediment Quality in Quebec [PDF 1.13 MB]       Quebec sediment quality criteria and application frameworks
Magar et al. (2009) Monitored Natural Recovery     Technical guide for contaminated aquatic sediment monitored natural recovery
Environment Canada (in press) FCSAP Supplemental Guidance for Ecological Risk Assessment       Supplemental Guidance to CCME (1997) with Modules on toxicity test selection, TRV derivation and causality
US Army Corps of Engineers Technical Notes and Technical Reports       Dredged material management, operations technologies, risk assessment and management
USEPA Contaminated Site Clean-Up Information: Sediments       Remediation of contaminated aquatic sediments
Sediment Management Work Group       Sediment assessment and management technical papers
ASTSWMO (2009)  Monitoring [PDF 775 KB]         Framework for long-term sediment monitoring

Appendix B - Data Quality Objectives (DQO)

The USEPA (2000, 2006) Data Quality Objective (DQO) process provides a useful tool toward assessing what decisions must be made, what information is available toward making those decisions, what additional information is needed, and how that information will be used in decision-making. Developing a conceptual site model (CSM; Appendix C) is one component of the first step of the DQO process.

The DQO process is a systematic planning process applicable when data are being used to select between two alternative conditions (e.g., compliance or non-compliance with a guideline, determining whether or to what extent management action is needed). The process begins with a problem statement, which requires identification of the project manager/decision makers, technical team members, and stakeholders; description of the specific problem to be investigated; assessment of this problem in terms of the CSM; and determination of resources available including limitations (budget, personnel and schedule).

The principal study questions are then identified, and possible alternative actions including potential operational options are defined. A decision statement is developed and possible multiple decisions are organized.

The information needed to reach a decision is identified. Sources for this information are determined, and an Action Level above which a management action will be taken is determined (e.g., the 95% confidence limits of a data distribution). Sampling and data analysis methods required to meet the data requirements are identified.

Target populations of interest are defined relative to the smallest subpopulation, area, volume, or time for which separate decisions must be made. As part of this component, the spatial boundaries of the study are specified. The time frames for collecting data and making a decision are also determined. Practical constraints on data collection are identified.

An appropriate population parameter (mean, median, percentile) is specified. Any exceedances of the Action Level are confirmed. A decision rule is developed (an “If…then” statement).

The following components of the DQO process should particularly be followed:

  • Specify tolerable limits on decision errors: The range of the parameter of interest is determined, and a null hypothesis is chosen. The consequences of an incorrect decision (Type I vs. Type II error) are examined. A range of values where the consequences are relatively minor (a “gray area”) is specified. Probability values are assigned to points above and below the Action Level that reflect tolerable probabilities for potential decision errors; and,
  • Optimize the design for obtaining data: The DQO outputs are reviewed and data collection design alternatives are developed. Mathematical expressions are formulated for each design. The sample size that satisfies the DQOs is selected.

Appendix C - Conceptual Site Model (CSM)

A conceptual site model (CSM) is a written description and visual representation of predicted relationships between ecological receptors and the stressors to which they may be exposed (CCME 1996, 1997; USEPA 1998, 2002b). CSMs represent many relationships. They may include ecosystem processes that influence receptor responses, or exposure scenarios that qualitatively link land-use activities to stressors. They may describe primary, secondary, and tertiary exposure pathways or co-occurrence among exposure pathways, ecological effects, and ecological receptors.

CSMs are integral to the problem formulation phase of HHRAs and ERAs - problem formulation is equivalent to Data Gathering (Steps 1 and 2 in this document). Reviews of ERA case studies have indicated many deficiencies that might have been avoided had more attention been paid to CSMs within the problem formulation (USEPA 1993). A well-constructed problem formulation (Steps 1 and 2, Sections 2.2.1 and 2.2.2) reduces the likelihood that significant pathways and receptors are incorrectly excluded, improves the alignment of the technical methods with appropriate measurement and assessment endpoints, and generally improves the consistency and transparency of the risk assessment. Effort spent on the CSM is particularly important for contaminated aquatic site risk assessments given that these assessments rely on weight of evidence (WOE) approaches and robust multi-media sampling programs, and generally require considerable effort to build consensus among stakeholders regarding appropriate decision criteria.

The CSM for aquatic sites should emphasize the type and magnitude of sediment contamination and define the pathways for contaminants to reach ROPCs. It is developed early in the Approach (Step 2, Section 2.2.2), provides the foundation upon which to obtain relevant and necessary new information (i.e., to address critical data gaps) about a suspect aquatic site, and is refined as new information becomes available (e.g., in Steps 3 and 5). Establishing the CSM early in the process (i.e., at Step 2) allows resources and subsequent efforts to focus appropriately on COPCs, ROPCs, and the exposure pathways between them.

Conceptual models are easily modified as knowledge increases; they highlight what is and what is not known, and they can be used to plan future work. They can be a powerful communication tool, because they provide an explicit expression of the assumptions and understanding of an aquatic site for others to evaluate. They also provide a framework for prediction and are the template for generating risk hypotheses (Appendix C).

CSMs for HHRAs and ERAs are developed from information about stressors, potential exposure, and predicted effects on an ecological entity (the assessment endpoint). Depending on why a risk assessment is initiated, one or more of these categories of information are known at the outset. The process of creating a CSM helps identify the unknown elements.

The complexity of the CSM depends on the complexity of the problem including, for example, the number of stressors, number of assessment endpoints, nature of effects, and characteristics of the aquatic site. For single stressors and single assessment endpoints, CSMs may be simple. However, when CSMs are used to describe multiple pathways and the interaction of multiple and diverse stressors and assessment endpoints (e.g., assessments initiated to protect ecological values), more complex models and several submodels will often be needed.

CSMs consist of two principal components: a set of risk hypotheses (Appendix D) that describe predicted relationships among stressor, exposure, and assessment measurement components, along with the rationale for their selection. The conceptual model also illustrates the relationships presented in the risk hypotheses (e.g., Figures 4 and 5).

Appendix D - Risk Hypotheses

Hypotheses are assumptions made in order to evaluate logical or empirical consequences, or suppositions tentatively accepted to provide a basis for evaluation. Risk hypotheses are specific assumptions about potential risk to assessment endpoints and may be based on theory and logic, empirical data, mathematical models, or probability models. They are formulated using a combination of professional judgment and available information on the aquatic site, potential sources of stressors, stressor characteristics, and observed or predicted ecological effects on selected or potential assessment endpoints.

Risk hypotheses may predict the effects of a stressor before they occur, or they may postulate why observed ecological effects occurred and ultimately what caused the effect. Depending on the scope of the risk assessment, risk hypotheses may be simple or complex.

Risk hypotheses represent relationships in the CSM and are not designed to statistically test null and alternative hypotheses. However, they can be used to generate questions appropriate for investigation, and predictions generated from risk hypotheses can be tested in a variety of ways, including standard statistical approaches. Risk hypotheses clarify and articulate relationships that are posited through the consideration of available data, information from scientific literature, and the best professional judgment of risk assessors developing the CSMs. This explicit process opens the risk assessment to peer review and evaluation to ensure the scientific validity of the work.

Although risk hypotheses are valuable even when information is limited, the amount and quality of data and information will affect the specificity and level of uncertainty associated with risk hypotheses and the CSMs. When preliminary information is conflicting, risk hypotheses can be constructed specifically to differentiate between competing predictions. The predictions can then be evaluated systematically either by using available data during the analysis phase or by collecting new data before proceeding with the risk assessment. Hypotheses and predictions set a framework for using data to evaluate functional relationships (e.g., stressor-response curves).

Early CSMs (Step 2) are normally broad, identifying as many potential relationships as possible. As more information is incorporated, the plausibility of specific hypotheses helps risk assessors sort through potentially large numbers of stressor-effect relationships, and the ecosystem processes that influence them, to identify those risk hypotheses most appropriate for the analysis phase. It is then that justifications for selecting and omitting hypotheses are documented. Examples of risk hypotheses (information that sets the problem in perspective and the proposed relationships that need evaluation) are provided below relative to contaminated aquatic sites:

  • Stressor-Initiated: Total Hg measured in sediments is converted to methyl Hg (meHg) and biomagnifies up the food chain. Hypothesis: Hg biomagnification may be occurring in fish feeding on invertebrates living in Hg-contaminated sediments;
  • Effects-Initiated: Benthic community structure is different for contaminated sediments than for reference sediments. Hypothesis: Differences in benthic community structure between contaminated and reference areas are due to toxic effects of one or more sediment contaminants; and,
  • Ecological Value-Initiated: Trout are important ecological, recreational, and economic species. The effects of heavily contaminated sediments on trout populations in areas where they breed and rear are not clearly defined. Hypothesis: Contaminants released to the water column from heavily contaminated sediments may adversely affect exposed trout populations.

Appendix E - Decision Matrix

Adapted from the COA (Tables 1 and 2, pp 16-18)

The table E1 provides guidance on how to determine the relative significance of results from Bulk Sediment Chemistry, Toxicity, Benthos Alteration and Biomagnification Potential analyses. The findings from each of these lines of evidence are classified into to a low, medium or high category and susquently entered into a decision matrix (Table E2) in order to determine a course of action.

Table E1: Ordinal Ranking for WOE Categorizations for Chemistry, Toxicity, Benthos and Biomagnification Potential
  Major Minor Negligible
Bulk Chemistry (compared to SeQG) Adverse Effects Likely:
One or more exceedances of SeQG-high
Adverse Effects May or May not Occur:
One or more exceedances of SeQG-low
Adverse Effects Unlikely:
All contaminant concentrations below SeQG-low
Toxicity Endpoints (relative to reference) Major: Statistically significant reduction of more than 50% in one or more toxicological endpoints Minor: Statistically significant reduction of more than 20% in one or more toxicological endpoints Negligible: Reduction of 20% or less in all toxicological endpoints
Overall Toxicity Significant: Multiple tests/endpoints exhibit major toxicological effects Potential: Multiple tests/endpoints exhibit minor toxicological effects and/or one test/endpoint exhibits major effect Negligible: Minor toxicological effects observed in no more than one endpoint
Benthos Alteration (multivariate assessment, e.g., ordination) “different” or “very different” from reference stations “possibly different” from reference stations “equivalent” to reference stations
Biomagnification Potential (relative to reference) Significant Possible Negligible
Overall WOE assessment Significant adverse effects:

elevated chemistry;

greater than a 50% reduction in one or more toxicological endpoints;

benthic community structure different (from reference); and/or

significant potential for biomagnification

Potential adverse effects:

elevated chemistry;

greater than a 20% reduction in two or more toxicological endpoints;

benthic community structure possibly different (from reference); and/or

possible biomagnification potential

No significant adverse effects:

minor reduction in no more than one toxicological endpoint;

benthic community structure not different from reference; and

negligible biomagnification potential

SeQG = Sediment Quality Guideline; EC = Effective Concentration.
Note that the overall definition of “no significant adverse effects” is independent of sediment chemistry.

The table E2 provides a decision matrix and suggested course of management action for 16 different combinations of test results arising from Bulk Sediment Chemistry, Toxicity, Benthos Alteration and Biomagnification Potential analyses.

Table E2: Decision Matrix for WOE Categorization
Based on Table 1; a dash means “or”. Separate endpoints can be included within each LOE (e.g. metals, PAHs, PCBs for Chemistry; survival, growth, reproduction for Toxicity; abundance, diversity, dominance for Benthos).
Scenario Bulk Sediment Chemistry Toxicity¹ Benthos Alteration² Biomagnification Potential³ Assessment
1 Negligible Negligible Negligible Negligible No further actions needed
2 Major-Minor Negligible Negligible Negligible No further actions needed
3 Negligible Negligible Major-Minor Negligible Determine reason(s) for benthos alteration
4 Negligible Major-Minor Negligible Negligible Determine reason(s) for sediment toxicity
5 Negligible Negligible Negligible Minor Fully assess risk of biomagnification
6 Major-Minor Major-Minor Negligible Negligible Determine reason(s) for sediment toxicity
7 Negligible Negligible Major-Minor Minor Determine reason(s) for benthos alteration and fully assess risk of biomagnification
8 Major-Minor Negligible Major-Minor Negligible Determine reason(s) for benthos alteration
9 Major-Minor Negligible Negligible Minor Fully assess risk of biomagnification
10 Major-Minor Major-Minor Negligible Minor Determine reason(s) for sediment toxicity and fully assess risk of biomagnification
11 Major-Minor Negligible Major-Minor Minor Determine reason(s) for benthos alteration and fully assess risk of biomagnification
12 Negligible Major-Minor Negligible Minor Determine reason(s) for sediment toxicity and fully assess risk of biomagnification
13 Negligible Major-Minor Major-Minor Negligible Determine reason(s) for sediment toxicity and benthos alteration
14 Negligible Major-Minor Major-Minor Minor Determine reason(s) for sediment toxicity and benthos alteration, and fully assess risk of biomagnification
15 Major-Minor Major-Minor Major-Minor Negligible Management actions required
16 Major-Minor Major-Minor Major-Minor Minor Management actions required

¹ Toxicity refers to the results of laboratory sediment toxicity tests conducted with a range of test organisms and toxicity endpoints. A positive finding of sediment toxicity may suggest that elevated concentrations of COPC are adversely affecting test organisms. However, toxicity may also occur that is not related to sediment contamination as a result of laboratory error, problems with the testing protocol, or with the test organisms used.

² Benthos alteration may be due to other factors, either natural (e.g., competition/predation, habitat differences) or human-related (e.g., water column contamination). Benthos alteration may also be related to sediment toxicity if a substance is present that was not measured in the sediment or for which no SeQG exist, or due to toxicity associated with combined exposure to multiple substances.

³ Per Table 1, significant biomagnification (Major) can typically only be determined in Step 6 of the COA (p 20); Step 3 of that same document only (pp 9-10) allows a determination that there either is negligible biomagnification potential or that there is possible biomagnification potential. However, there may be site-specific situations where sufficient evidence is already available from fish advisories and prior research to consider biomagnification at a site significant; this would be determined in Step 1 (examination of available data) of the COA (p 7). Thus, for example, if significant biomagnification were indicated in Scenario 5, above, management actions would be required. The other three LOE do allow for definitive determinations in prior Steps of this Framework.

Definitive determination possible. Ideally elevated chemistry should be shown to in fact be linked to observed biological effects (i.e., is causal), to ensure management actions address the problem(s). For example, there is no point in removing contaminated sediment if the source of contamination has not been addressed. Ensuring causality may require additional investigations (Section 5.3 of the COA [pp 29-30]). If bulk sediment chemistry, toxicity and benthos alteration all indicate that adverse effects are occurring, further assessments of biomagnification should await management actions dealing with the clearly identified problem of contaminated and toxic sediments adversely affecting the organisms living in those sediments. In other words, deal with the obvious problem, which may obviate the possible problem (e.g., dredging to deal with unacceptable contaminant-induced alterations to the benthos will effectively also address possible biomagnification issues).