Recent seabed remediation work undertaken by Department of National Defence (DND), Public Services and Procurement Canada (PSPC), and Defence Construction Canada, has provided an opportunity for some exciting archaeological discoveries in Esquimalt Harbour, a federally administered harbour located in British Columbia. This presentation summarizes artifact recovery during remediation and how the analysis of artifacts and historical structural elements recovered from the seabed sediments reflects the previous land uses at Esquimalt Harbour.

Archaeological overview assessments conducted in advance of seabed remediation established archaeological potential based on known archaeological sites and documented historical use on the adjacent land, land form and sea level changes, and review of historical disturbances to the seabed due to the construction of infrastructure and dredging. Careful analysis of historical charts and the results of previous geotechnical and geo-environmental borehole testing programs revealed that while much of the original coastline has been altered by various development activities, intact intertidal and subtidal deposits remain in the harbour that have potential to contain significant archaeological deposits. In some locations, archaeological testing and underwater documentation was further conducted to better understand the archaeology of the seabed prior to remediation.

Where archaeological resources were identified in the seabed, the footprint for remediation could sometimes be modified to avoid impacts to the archaeological site. In other instances, potential archaeological impacts were mitigated as a result of sediments being screened for unexploded explosive ordnances (UXO). The UXO screening system used in Esquimalt Harbour was set up on a processing barge where dredgeate was subject to a high pressure water spray and sorted by size using a series of sieves as fine as 0.5 cm. The process enabled the detection and removal any UXO which might be contained within the dredgeate, a possibility owing to the harbour’s long use as a naval base. Observer personnel standing at five different ‘pick stations’ on three different conveyor belts between screens could also collect pre-historic and historic archaeological material as it moved along the conveyor belts. Collected material was then examined by an archaeologist on the barge.

During remediation, participants from the Esquimalt and Songhees Nations were often employed as observer personnel on the barge to spot and collect cultural material. This is an example of the full involvement and integration through archaeology of First Nations whose reserve lands border the harbour. Indigenous engagement is helping DND and PSPC build a strong, respectful relationship with their First Nations neighbours, for whom the past, present and future use of the harbour is a key issue and concern.

Esquimalt Harbour is rich in archaeological resources. The use of the harbour by the ancestors of First Nations extends minimally five thousand years into the past and likely longer. The harbour has seen industrial/commercial use for the last 170 years. The artifacts collected during remediation conducted at Canadian Forces Base Esquimalt reflect and provide considerable insight into the harbour’s use for millennia by First Nations, as well as its historical uses by the navy and civilian industries.

Parks Canada Agency (PCA) has identified 90 sites along the Trent Severn Waterway and the Rideau Canal that will require either replacement, upgrading or repairing of water management structures such as dams, locks and bridges. A number of these sites may have sediment contamination arising from historical and on-going activities along the waterways, such as mining, lumber, foundries, milling, manufacturing and commercial transport, as well as discharges from upland industrial sites.

In collaboration with Public Services and Procurement Canada (PSPC) on behalf of PCA, a screening tool was developed to prioritize the sites for sediment assessments in advance of construction activities. The objective of the screening exercise is to identify sites where mobilization of contaminated sediment may pose potential environmental risk. The prioritization matrix pre-screens sites according to the type of planned construction activities and presence of sediment in the work zone, and then evaluates potential risk through ranking factors in four subcategories: contaminant source; sediment transport pathway; potential impacts on human health; and, potential impacts on fish habitat. Information used to evaluate the categories is provided primarily through a land use analysis using a geographic information system, as well as simplified Phase I environmental site assessments (ESAs) including historical reviews, surveys of fish habitat type and sensitivity carried out for the sites in support of the environmental assessment, and a review of planned construction activities for each site. Prioritization factors in the “contaminant source” section of the matrix were weighted twice as high as the other factors for the following reasons: 1) there is good land use and historical information available to score these factors and high confidence in the evaluation; and, 2) the existence of past and present sources of contamination is a primary driver of potential risk.

The outcomes of the prioritization matrix are used to classify the sites into three categories: sites that do not require sediment assessment (no to low potential risk of contamination); the sites that do require sediment assessment (high potential risk); and, an intermediate category where further review by PCA is recommended to determine whether a sediment assessment is needed. A case study site prioritization exercise was used to calibrate the screening tool using information from nine sites in the Trent Severn Waterway. Group reviews of the outcomes concluded that the site rankings and classification boundaries appeared reasonable given PCA knowledge of the locations. The prioritization matrix represents a valuable management tool to guide decisions regarding the need for sediment assessments of sites in the Trent Severn Waterway and Rideau Canal systems prior to the onset of construction activities.

Food chain models are frequently used during risk assessments to evaluate ecological risks ranging from sediment contaminants to greater trophic level receptors. These models use tissue data and dietary intake models to estimate contaminant exposures to receptors of concern. Model use must consider the mobility and home range of the prey species, as well as the feeding behaviours and sensitivity of the receptors. In the case of a larger harbour site with different subareas and prey species that are both localized and wide-ranging, these models can be complex. However, when properly used, the models can directly support good remediation planning.

Remediation planning was recently conducted within a 2.5-square-kilometre area of Victoria Harbour, British Columbia. Early risk evaluations demonstrated potentially significant risks (defined as a hazard quotient greater than 1.0) from exposure to polychlorinated biphenyls (PCBs) and dioxins/furans for two birds, the cormorant and great blue heron. Initial modeling outputs were insufficient to determine what portions of the harbour caused this elevated risk. To support remediation planning, additional tissue data were collected to quantify localized risk levels within each harbour subarea, each with different levels of sediment and stormwater pollutants. Supplemental tissue sampling focused on certain species exhibiting high site fidelity – small sculpin and shore crabs – that were more likely to vary in tissue PCB and dioxin/furan levels than other species. Testing data confirmed large differences in sculpin and crab tissue pollutant levels between the different subareas. Refined risk estimates incorporating the localized species mentioned and wide-ranging prey species demonstrated that elevated risks to birds were only present within a single subarea of the harbour. That area was targeted for further remedial evaluation. The refined food chain model was used during development of the options evaluation and remedial action plan to quantify the risk reductions achievable under different remedial scenarios. Dredging and clean sediment backfill were ultimately selected for final remediation of this sediment hotspot area.

The inner harbour of the Kingston urban core (KIH) has a legacy of historical and active sources (e.g., former municipal landfill, municipal storm sewers, former lead/zinc smelter, former tannery, former coal gasification plant, active marina and shipyard sources) which led to sediment contamination by chromium, PAHs, PCBs, mercury and other constituents. Multiple tiers of past investigations, multiple federal custodians and stakeholders, and multiple groups providing interpretative reports and technical advice, made it challenging to discern a clear, comprehensive, and systematic approach to risk management. Therefore Public Services and Procurement Canada (PSPC), on behalf of Transport Canada and Parks Canada, issued a contract to integrate historical information with recent targeted investigations in the harbour, and direct the project toward risk management and remedial strategies.

Over the last decade, a wealth of information has been collected in KIH, both in terms of characterizing the spatial extent and magnitude of contamination and in characterizing the effects of contaminants to organisms. Multiple rounds of field studies and desktop evaluations of risks to humans and aquatic life have been conducted. These studies have been reviewed at milestone reporting stages by the Federal Contaminated Sites Action Plan (FCSAP) expert support departments, which provide oversight of the technical competency of environmental investigations. Most of the investigations have followed the Canada-Ontario Decision-Making Framework for assessment of Great Lakes Contaminated Sediment, which uses an ecosystem approach to sediment assessment; this framework is intended to standardize the decision-making process while also being flexible enough to account for site-specific considerations.

This presentation summarizes the results of the risk refinement and synthesis stage, which drew together available risk assessment findings, addressed FCSAP expert support concerns, and provided the final scientific analysis for input to the conceptual remedial options analysis and stakeholder consultation stages of the project, which are ongoing under the direction of PSPC.

The risk synthesis addressed information gaps from the detailed quantitative assessment (DQA) stage, and included a sediment gap analysis for the Parks Canada property, a literature assessment of potential causes of bottom fish deformities in KIH, a review of potential sources of contaminants in the southwest portion of the Transport Canada water lot, and a refined sediment investigation in the southwest portion of the Transport Canada water lot (including surface grabs and core profiling). The deliverable also evaluated management areas within the KIH for which multiple risk pathways (human health, wildlife health, fish health, and benthic community health) and multiple contaminant types indicated potential risks, in order to identify areas for which the management priority was greatest.

Public Services Procurement Canada (PSPC) Environmental Services, in coordination with the Department of National Defence (DND), designed and implemented a sediment remediation project during 2016 and 2017 at DND Colwood in Esquimalt Harbour on Vancouver Island, British Columbia. The primary remediation methods were dredging (removal of approximately 21,500 cubic metres of contaminated sediment) and off-site disposal of contaminated materials at an upland disposal facility, backfilling, and management of dredge residuals via placement of residuals management cover material. In addition to contaminated sediment removal, backfilling, and residuals management, it was anticipated that the dredged material could contain suspected unexploded ordnance (UXO), and PSPC included dredge material processing/screening be completed to remove any encountered UXO. Dredge material processing was also performed to help identify and segregate historically, archaeologically, architecturally, or paleontologically significant structures, sites, or other items. Furthermore, multiple remediation projects were scheduled to occur at other DND facilities in the harbour, resulting in a reduction of contractor or equipment availability and berthing space for DND vessels. These factors resulted in operational constraints at the Colwood Jetties facility and required a firm schedule be developed for implementation of the planned remediation activities.

This presentation provides a summary of work completed and focuses on discussion of key construction challenges and lessons learned following implementation of the project. Key challenges included processing dredged sediment and debris to screen for and segregate UXO prior to transporting sediments to the offloading facility for disposal, coordinating remediation activities with evolving operational requirements at the facility, and addressing water quality considerations regarding placement of backfill and residuals management cover material. Additional challenges included placing backfill material in under-pier areas and managing dredging and material processing production rates to meet schedule requirements for the project.

Following completion of construction activities and during closeout of the project, PSPC completed a detailed analysis of lessons learned to inform and revise the design and implementation approach for future projects. The presentation will also provide a discussion of those lessons learned and how they may be applied to other sediment remediation projects throughout Canada that are in their planning and design phases.

Ecological risks assessments for contaminated sites utilize either published toxicity reference values (TRVs) or TRVs that are specifically developed for a particular site. The Federal Contaminated Sites Action Plan (FCSAP) encourages the development of site-specific TRVs and has developed guidance on scientifically defensible methods for TRV development applicable to metals and other contaminants. However, for many federally managed sites, developing site-specific TRVs is beyond the scope of the remediation or risk management project. Instead, risk assessors often choose an existing published TRV to assess the risk to ecological receptors. Published TRVs vary widely in their numeric values, derivation methods, uncertainties, and in the level of protection they provide. Subsequently, the outcome of the risk assessment can vary depending on which published TRV is applied. This leads to inconsistencies when similar sites are assessed by different practitioners, organizations or regions.

To streamline risk assessments where development of site-specific TRVs is not feasible, FCSAP has developed an approach to evaluate published TRVs and identify those which are best suited for use as standard default TRVs. This approach evaluates available TRVs based on how well they align with existing FCSAP guidance. A set of ten criteria to identify TRVs’ merits, limitations and uncertainties was used, including the use of dose-response data or point estimate effects data, uncertainty factors, allometric scaling, biological endpoints, test species, and protection levels. FCSAP has applied these criteria to select recommended default wildlife TRVs for fourteen metals and nine organic compounds, presented in FCSAP ERA Module 7. Federal contaminated sites managers and practitioners can also use these detailed evaluations to prioritize where further site-specific TRV development work may be warranted.