Following federal guidance for assessment of contaminated water lots often requires examination of resident benthic communities as a line of evidence. This assessment of resident community health provides site-specific information against which chemical and toxicological lines of evidence can be compared. In many instances, grab sampling, sieving and taxonomic enumeration of organisms is adopted as a default method, with common measurement endpoints of community composition alteration and/or benthic indices. The context of many federal contaminated sediment sites is ill-suited to the application of these techniques, whereas in other cases the community structure tool proves highly effective. The goal of this presentation is to evaluate the site conditions that either favour or discourage taxonomic evaluation as a key line of evidence, including consideration of study objectives, scale of contamination, nature of contamination sources (gradients, point or non-point sources, type of chemical stressors), complexity of habitat, and potential confounding factors in the study design. Alternate methods, including sediment profile imaging and underwater video, are evaluated in terms of their advantages and disadvantages, using examples from sediment quality assessments conducted for public sector clients. Examples of criteria include statistical (ability to discern responses, confounding factors), ecological (biological and functional importance of various measurements), and practical (cost, logistics) considerations. Consideration of these factors prior to study design should increase the chance of picking the “right tool for the job” and better align the results with the decision rules for interpreting biological significance in the evaluation framework. 

Finfish are not commonly included in ecological risk assessments (ERA). Reasons offered for excluding finfish from ERA include their ability to avoid exposures; the relative insensitivity of fish, compared aquatic plants and invertebrates, to the toxic effects of some contaminants; and, the lack of guidance on ERA for finfish. However, fish are equally or more sensitive to the toxic effects of some contaminants (e.g., ammonia, nitrite, cadmium, selenium, some PAHs) than aquatic plants and invertebrates; some small-bodied fish species have small home ranges and high site fidelity; and, some species may have relatively high exposure to contaminants that bioaccumulate or biomagnify in aquatic food webs. Therefore, in some cases, finfish may be a relatively sensitive receptor that warrants inclusion in ERA as a receptor of concern.

This presentation provides a case example of an ERA for finfish that was conducted as part of a broader ERA of contaminated sediments managed by Transport Canada in Victoria Harbour, Victoria, B.C. First, a conceptual model of exposure and susceptibility was developed to identify candidate sentinel finfish species for detailed evaluation. Lines of investigation used to support the development of conceptual models included fish community surveys, a literature review of the biology and ecology of fish species known to occur in Victoria Harbour, and measurement of biomarkers of exposure (hepatic EROD and gill metallothionein expression) and stable carbon and nitrogen isotopes in fish species that were observed to be relatively abundant in exposure and reference areas. Second, risks to seven candidate sentinel species (tidepool sculpin, great sculpin, Pacific staghorn sculpin, ribbed sculpin, snake prickleback, English sole and three-spined stickleback) were assessed using direct measures of effect based on Environment Canada guidance for assessing potential impacts to fish community health under the Environmental Effects Monitoring (EEM) program; measurement endpoints included abundance, size, condition, liver weight and gross pathology. There were differences between exposure and reference areas for the following endpoints and species: (1) size distribution among Pacific staghorn sculpin, tidepool sculpin, and great sculpin; (2) abundance of tidepool sculpin; and, (3) liver weights of Pacific staghorn sculpin. The observed differences in population characteristics for tidepool sculpin and Pacific staghorn sculpin were consistent with contaminant-related adverse effects, but there were also plausible habitat-related explanations for the observed differences. 

The overall weight-of-evidence conclusions of the finfish ERA were that (1) tidepool sculpin had the highest risk of adverse effects, relative to other finfish species; (2) the risks of adverse effects to tidepool sculpin ranged from low to moderate; and, (3) uncertainty regarding the risk of adverse effects to tidepool sculpin was high. The finfish ERA for Lot 17 in Victoria Harbour identified the species most suitable for further assessment or monitoring and complimented the ERA conclusions for other aquatic receptors of concern. 

Following the discovery of gold in the Yellowknife area of the Northwest Territories, Giant Mine officially opened in 1948. After the mine closed in 2004 the care and control of the mine fell to Indigenous and Northern Affairs Canada (INAC), and attention focused on the environmental issues left behind, including the arsenic trioxide stored in underground chambers. The Giant Mine Remediation Project was created in 2005 with the overall goal to protect human health and safety, and the environment.

The site lies within the Mackenzie Valley watershed, and is regulated by the Mackenzie Valley Resource Management Act (MVRMA). The MVRMA is federal legislation aimed at creating an integrated system for protecting the lands and waters within the Mackenzie Valley watershed. Since the site is under the care and custodianship of INAC, it is also subject to other federal acts, such as the Canadian Environmental Protection Act, the Fisheries Act and the Migratory Birds Convention Act, among others. It is also situated within the municipal boundaries of the City of Yellowknife, and so is impacted by the City’s bylaws and permitting requirements.

The Project has recently completed a seven-year environmental assessment (EA) process under the MVRMA, which resulted in 26 legally binding measures being incorporated into the project scope.

The Project Team is now proceeding with a clearly defined list of requirements established through the process for the project. Specific components of the project require stakeholder input before being included in the updated consolidated project description. Two such components currently undergoing public consultation are the relocation of the treated effluent outfall and the remediation of Baker Creek.

Baker Creek is a small, intermittent stream that flows through the Giant Mine site and drains the general mine/mill complex area. Treated effluent is discharged into Baker Creek during the open-water season, usually a two to three month period between July and September. Water flow in Baker Creek is seasonal and limited to particular periods during the open water season; flows in the upper portions of the creek cease during the summer months, while the input of treated effluent sustains flows in the lower portions of the creek during the entire period of discharge. As part of the remediation plan, the current treated effluent discharge will be removed from Baker Creek and relocated, likely into Yellowknife Bay of Great Slave Lake.

There are two EA measures directly applicable to the remediation of Baker Creek. One EA measure requires that the water quality at the outlet of the creek channel must meet site-specific water quality objectives. The second EA measure requires that remediation of the creek ensures that water quality changes associated with Baker Creek will not adversely affect benthic invertebrates, plankton or fish in the vicinity of the creek outlet in Great Slave Lake. In addition, the outflow of Baker Creek must not increase arsenic concentrations in Great Slave Lake, must not affect traditional or recreational users, and must not adversely affect areas used as sources of drinking water. Meeting these EA measures will prove challenging as treatment of the Baker Creek water is not a feasible option.

Typically, water quality objectives are based on the Canadian Council of Ministers of the Environment’s (CCME) Canadian Water Quality Guideline (CWQG) for the Projection of Freshwater Aquatic Life. However, the CCME CWQGs are generic and designed to be protective of the most sensitive species on a national scale. Giant Mine is located within the Yellowknife Greenstone Belt and arsenic concentrations within this area are naturally elevated. As such, using the generic CCME CWQG for arsenic is not appropriate. Work is currently underway to develop site-specific water quality objectives for arsenic at the outlet of Baker Creek; additional parameters are also being screened and assessed and site-specific water quality objectives will be developed, as appropriate.

This presentation will describe the technical development of site-specific water quality objectives for Baker Creek. The public consultation and engagement requirements associated with this work will also be discussed.