Contaminated Sediment: A Better Assessment Approach
Background
In May 2008, the Ministry of the Environment (MOE) posted its decision to adopt the Canada-Ontario Decision-Making Framework for Assessment of Great Lakes Contaminated Sediment (“COA Framework”). Contaminated sediment is one of the critical factors contributing to degraded environmental conditions and the impairment of beneficial uses of many Areas of Concern (AOCs). Contaminants originate from industrial, municipal and non-point sources, and enter the Great Lakes via rivers, streams, pipes, discharge outlets and atmospheric deposition, accumulating in bottom sediments.
Contaminants can degrade water quality and adversely affect benthic (bottom-dwelling) organisms and the predators that consume them. Although some contaminants readily break down, others are persistent and can accumulate in the fatty tissues of organisms, and concentrate up the food chain in a process called biomagnification.
The decision to remediate should be driven by the magnitude of health risks to humans and wildlife from continued exposure to the contaminated environment. The selection of the appropriate remediation approach should consider whether the removal, treatment and disposal of the contaminated sediments would cause greater harm than leaving them in place.
In 1998, while MOE and Environment Canada (EC) were jointly involved in a sediment assessment and remediation project in the Cornwall area, staff noticed that contaminated sediments were assessed differently by the public and private sector, resulting in inconsistencies in clean-up decisions. This prompted EC and MOE to commit to developing a harmonized science-based sediment assessment framework. Description
The COA Framework is designed to identify and assess contaminated sediment. It harmonizes federal and provincial approaches on sediment assessment and builds upon MOE’s 1993 and 1996 provincial sediment guidelines. The COA Framework uses an ecosystem approach to assess sediments and considers possible effects on benthic and other aquatic organisms, including the potential for contaminants to biomagnify up the food chain. For a detailed review, see Section 4.4 of the Supplement to this Annual Report.
The COA Framework is intended to standardize the decision-making process province-wide while maintaining enough flexibility for site-specific considerations. The COA Framework process is outlined in a step-by-step flowchart and a decision-making matrix that are used to determine appropriate remedial actions or the necessity for additional assessments. The analysis used in the decision-making process incorporates data from four “lines of evidence” (LOE): sediment chemistry, sediment toxicity, benthos community alteration, and the contaminant’s biomagnification potential. It also relies on four “guidance rules,” which generally emphasize that decisions will be based on biological data, and not solely on chemical analysis.
The COA Framework, along with the 1993 and 1996 sediment guidelines, were integrated into the Guidelines for Identifying, Assessing and Managing Contaminated Sediments in Ontario: An Integrated Approach, May 2008 (“2008 MOE Guideline”). This document is intended to present all MOE’s guidance on managing contaminated sediments in Ontario in a clear and transparent package.
Implications of the Decision
The COA Framework empowers decision-makers to evaluate what levels of contamination are acceptable in the short-term and how to proceed when sediments are considered clean; and when contamination is severe enough to warrant significant remedial action. These are key decisions for determining whether a site needs to be remediated.
The COA Framework, which is embedded in the 2008 MOE Guideline, can be applied to contaminated sediments across the province. Using an ecological risk assessment, the COA Framework standardizes the decision-making process while recognizing site-specific conditions and including input from professional judgment. The matrix helps ensure consistency and transparency by deriving appropriate actions based on the data from the four LOE entered into the matrix. Furthermore, MOE will rely on the sound science and transparent process to issue provincial clean-up orders that are more likely to withstand a legal challenge.
One key challenge when dealing with contaminated sediments is the cost required to assess and remediate a site. By identifying priority sites, the assessment process aims to ensure that limited resources are properly allocated. Otherwise, the COA Framework does not address social and economic considerations. However, these matters are acknowledged as important in the risk management section of the 2008 MOE Guideline.
MOE relies on the 2008 MOE Guideline for all its assessments and remediation projects. Where consultants, for example, use a different approach than the 2008 MOE Guideline, MOE will require them to provide the requisite information specified in the 2008 MOE Guideline and to obtain any outstanding information.
ECO Comment
By developing an integrated and harmonized contaminated sediment assessment and decision-making framework Ontario has met a commitment it made in the 2002 COA. The ECO is hopeful that the COA Framework will result in a more effective assessment process that assists in the identification and remediation of polluted waterbodies in Ontario.
The ECO commends MOE for creating a province-wide framework that enhances the scientific assessment process for contaminated sediments, and for carrying out comprehensive public consultation and national and international peer-review.
Scientists and decision-makers need to understand the ecological impairments resulting from contaminated sediments because this information informs the extent and scope of any necessary remedial and rehabilitative actions. In order to maintain policies that are up-to-date and current, the ECO urges MOE to regularly review the 2008 Framework and 2008 MOE Guideline to ensure that scientific advancements are integrated into these documents.
Ultimately, the effectiveness of the COA Framework will depend on factors beyond its scope, including government leadership, the actual use of the 2008 MOE Guideline, and adequate funding to carry out the assessments and remediation. Complementary provincial efforts are also required to curb the sources of contaminants that make their way into the environment.
The ECO will continue to follow developments on Great Lakes protection and the renewal of the Canada-Ontario Agreement Respecting the Great Lakes Basin in 2010. We will monitor whether AOC remediation
remains a priority for Ontario, and whether adequate goals and commitments are made to address that priority.
| This is an article from the 2008/09 Annual Report to the Legislature from the Environmental Commissioner of Ontario. |
Citing This Article:
Environmental Commissioner of Ontario. 2009. "Contaminated Sediment: A Better Assessment Approach." Building Resilience, ECO Annual Report, 2008-09. Toronto, ON : Environmental Commissioner of Ontario. 74-76.
