Industry, government mark successful conclusion of $20-million cleanup in Thunder Bay Harbour
Completion of the $20-million, seven-year cleanup of severely contaminated sediment at the Northern Wood Preservers site has moved Thunder Bay Harbour a significant step closer to being removed from the list of Canadian Areas of Concern (AOCs).
Representatives from the federal and Ontario governments as well as industry and local organizations gathered in Thunder Bay last week to tour the cleanup site and mark the official end of the project, known as Northern Wood Preservers Alternative Remediation concept, or NOWPARC.
The project, whose final cost was more than double the original estimate of $9.3 million, persevered through unexpected surprises, stumbling blocks and occasional tensions among the five parties involved to become what all, by consensus, consider a case study in commitment as well as expertise and technological innovation.
"By being able to draw upon the diverse skills and technical abilities of our member parties, the team was able to bring a complex environmental project to completion," said Francine Dorion, vice-president of environment and sustainability for Abitibi-Consolidated, the project management lead. "It was a powerful example of how synergy can be created through commitment, perseverance, goodwill, knowledge and effort," she added.
Cleaning up what residents referred to as the "Thunder Bay blob" involved isolating the source of the contamination, removing and treating sediment with the highest concentrations and containing the remainder, and creating five hectares of new, high-quality fish habitat.
The project centred around the Northern Wood Preservers (NWP) facility. Over the past century the property has been used by various owners as an industrial site; wood preserving activities were carried out there for more than 60 years.
The creosote used for this purpose resulted in contamination of the harbour sediment with levels of polycyclic aromatic hydrocarbons (PAH), chlorophenols, dioxins and furans high enough to warrant the site's inclusion on the AOC list. Of the original 17 Canadian sites on the International Joint Comission (IJC) list, Thunder Bay Harbour is ranked second only to Hamilton Harbour.
Discussions about how to clean up the site began in 1993; a subsequent site assessment study defined four zones of contamination: Zone 1, consisting of a creosote pool (the "blob"); Zone 2, an area of acute toxicity (over 150 parts per million (ppm) of PAH), where sediment removal was required; Zone 3, an area of chronic toxicity requiring isolation (30-150 ppm PAH); and Zone 4, an area of no measurable effects (less than 30 ppm PAH).
NOWPARC, developed by NWP, Abitibi-Consolidated and Canadian National Railway (CN) outlined a three-stage strategy for dealing with these zones. It was submitted to Environment Canada (DOE) and the Ontario Ministry of Environment (MOE) for funding assistance.
The original projected cost of $9.3 million for the cleanup more than doubled, to $20 million. DOE's Ontario region contributed $5.5 million, with the companies and the MOE together providing the remaining $14.5 million.
For Zones 1 and 2, the strategy called for dredging and treating approximately 11,000 cubic metres (m3) of highly contaminated sediment. Zone 3A work would include building a rockfill berm to contain some 21,000 m3 of less contaminated sediment and capping it with clean fill to isolate it from the aquatic environment. In the fourth zone, designated 3B, approximately 28,000 m3 of marginally contaminated sediment would be left outside the berm to recover naturally.
The actual work began in the latter half of 1997 and was substantially completed by late 2004, with finishing touches carried out through early 2005.
Two of the major stumbling blocks during the project related to treatment and isolation of the contaminated sediment. NOWPARC initially proposed biological remediation of the sediment, but the process was found unable to bring contaminant levels down to meet the required criteria. Consequently, some 11,000 m3 (17,000 tonnes) of highly contaminated sediment were shipped to Envirogreen Technologies' treatment facility near Princeton, BC for thermal processing. The treated material will be used for backfill at a mine site.
The extra remedial work increased the treatment costs from the budgeted $2.3 million to $4.3 million.
Isolation costs mushroomed from $500,000 to $3.6 million when it was determined that NOWPARC's originally specified low-permeability clay barrier, to be built around the NWP pier, would not be adequate to ensure consistent containment of remaining contaminants on the site. The clay barrier was intended to operate in conjunction with a groundwater control system which would direct groundwater toward the pier and away from Lake Superior (this system was built and has been functioning effectively).
As a result, a steel sheet pile wall-a Waterloo Barrier(r)-was constructed to supplement the clay barrier and compensate for any possible permeability. The barrier, installed in 2001, covers an area of approximately 6,000 square metres (m2), placed along a 660-metre section around the NWP pier.
The challenges associated with NOWPARC also provided a showcase for technical and engineering expertise. A portion of the environmental dredging involved in the project, for example, made use of the Cable Arm(tm) clamshell bucket, whose unique design minimizes water column disturbance as the dredged material is being lifted. Other design features also serve to control environmental impacts.
As part of the stormwater and groundwater control portion of the project, NWP had a new wastewater treatment plant built on-site. Incorporating granular activated carbon (GAC) filtration, the facility releases effluent of near drinking water quality.
The dredging and infilling operations that were part of NOWPARC consumed an area of the lake approximately 150,000 m2 in size. To compensate for this, about 48,000 m2 of new or altered aquatic habitat were created, including 11,000 m2 of reclaimed land adjacent to an existing NWP marsh site. This has included site treatments along the rockfill containment berm to create a variety of fish habitats, and planting of vegetation in newly-created buffer zones.
Monitoring of these areas has so far indicated that fish and wildlife are moving into the prepared areas and vegetation is thriving. Monitoring of the harbour sediment as well as the fish habitat and buffer zone is being conducted and will continue for the long term.
More information is available from Roger Santiago at Environment Canada, 416/739-5876, E-mail firstname.lastname@example.org, or Patricia Inch at the MOE's northern region office, 807/475-1723, E-mail email@example.com.