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ESQUIMALT - REMEDIATION 

 
 
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Evaluation and Design of Marine Habitat Offsetting for Multiple Projects Near Esquimalt Harbour, British Columbia
Jessica Wilson1, John Readshaw1, Doug McMillan1, Jeff Lainsbury1, Scott Irwin2
1SNC-Lavalin
2Defense Construction Canada

The objective of this presentation is to discuss the coastal engineering aspects of three Department of National Defence projects, including the evaluation of offsetting options, design approach, and conceptual design.

Abstract

Multiple upgrade projects have been proposed by the Department of National Defense for coastal areas located on the southwestern tip of Vancouver Island, British Columbia. The upgrades included two projects in Esquimalt Harbour (Small Boat Float [SBF] and Fleet Dive Unit [FDU]) and one project in Pedder Bay (PB; Rocky Point Jetty). Each of the projects consisted of a large component of historically contaminated seabed sediments, and, without habitat offsetting, the proposed projects would further reduce habitat supply and diversity in the area.

The first portion of the project was completed by SNC-Lavalin Inc. for Defense Construction Canada in fiscal year 2015/2016, and included a marine habitat options analysis for the three proposed projects. As part of this analysis, SNC-Lavalin developed a framework to assess habitat offsetting options by using habitat offset criteria, reviewing the requirements of Fisheries and Oceans Canada (DFO) with respect to the production of commercial, recreational, and aboriginal (CRA) fisheries, and considering site-specific physical environments and coastal engineering requirements. The results of the habitat options analysis were then used to inform the selection of three engineering options for further study and design, including:

(1)        Small Boat Float – Enhanced revetment;

(2)        Fleet Dive Unit – Submerged rock reefs; and,

(3)        Rocky Point Jetty – Intertidal beach.

The ‘Marine Habitat Offsetting Conceptual Design’ and ‘Marine Habitat Offsetting Engineering Design Basis’ reports subsequently summarized the tasks required in developing the conceptual designs, feasibility, and cost-estimates for each project. The reports contained Class-C cost estimates to conduct investigative environmental studies of each area (e.g., dive surveys, geotechnical/environmental data desk-top review), as well as estimates for engineering/design and construction. This presentation will focus on the coastal engineering aspects of the three projects, including the evaluation of offsetting options, design approach, and conceptual design.

 
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Controlling Suspended Sediments During Phase 2 Sediment Remediation Dredging at the Esquimalt Graving Dock
Norm Healey1, Dan Berlin2, David Mckeown3, Christopher Major4, Andrew Mylly4, Dave Osguthorpe4, Matt Woltman2, Tom Wang2, Ryan Hill1, Dave Kettlewell5
1Azimuth Consulting Group Partnership
2Anchor QEA, LLC
3SLR Consulting (Canada) Ltd.
4Public Services and Procurement Canada
5SNC-Lavalin Inc.

The objective of this presentation is to describe the design of a temporary resuspension barrier to prevent the recontamination of previously remediated sediments surrounding the Phase 2 remediation area of the Esquimalt Graving Dock and the methods and results of performance water and sediment quality monitoring to assess its effectiveness.         

Abstract

The Esquimalt Graving Dock (EGD) is located in Esquimalt Harbour on Vancouver Island, British Columbia, and is managed by Public Services and Procurement Canada (PSPC). The EGD is the largest solid-bottom commercial dry dock on the West Coast of the Americas and has been used for the repair and maintenance of military and civilian vessels since 1927. Historic sediment contamination includes a broad range of chemicals, such as metals, polychlorinated biphenyls (PCBs), tributyltin (TBT), and polycyclic aromatic hydrocarbons (PAHs).

In support of objectives of the Federal Contaminated Sites Action Plan (FCSAP), PSPC developed a multi-phase remedial action plan and engineering design for cleaning up contaminated sediments in and adjacent to the EGD waterlot. Phase 1A was completed in 2013 and included installation of a sheet pile perimeter wall around the existing timber jetty structures to prevent re-contamination of remediated sediments during subsequent phases of the project. Phase 1B was completed in March 2014 and included 144,000 cubic metres (m3) of remedial dredging and off-site upland disposal of contaminated sediments. Phase 2 activities were conducted from October 2015 through December 2016 and consisted of demolition of the timber-piled South Jetty structures, re-driving of the perimeter sheet pile wall and construction of a temporary re-suspension barrier (TRB), remedial dredging and off-site upland disposal of 40,000 m3of contaminated sediments, placement of seabed capping materials, placement of slope armour, and modifications to the remaining concrete jetty structure. 

The EGD waterlot sediment remediation project is the largest sediment remediation dredging project ever carried out by the Government of Canada. This presentation describes the design and construction of the TRB and performance monitoring conducted during Phase 2 remediation to prevent and assess recontamination of the surrounding, previously remediated areas of the EGD waterlot.

The TRB design required the re-drive of the sheet pile perimeter wall and installation of a floating silt curtain to fully contain re-suspended sediment, with a unique system to seal the curtain to the sheet pile wall. Operational controls and monitoring were required to limit re-suspended sediments generated from several dredging methods in open water and limited access areas, and to avoid recontamination of capping material placed following dredging in each construction zone.

Project-specific water quality performance criteria were developed to protect aquatic life in the marine receiving environment and to ensure the effectiveness of the TRB in preventing recontamination of the previously remediated areas of the EGD waterlot. This resulted in relatively stringent water quality performance criteria that, for some parameters, were within the range of ambient variability previously observed in Esquimalt Harbour. The water quality monitoring plan relied extensively on in-situ measures of water quality to provide the spatial and temporal resolution necessary to adequately distinguish project-related changes in water quality from ambient variability and to enable timely response actions. Over 20,000 field measures of water quality were taken and approximately 400 samples were collected for laboratory measurement of TSS, metals, and PAHs. Measured water quality parameters met, with few exceptions, the water quality performance criteria.

Surface sediment samples were collected and diver surveys were conducted outside of the Phase 2 work boundaries to establish baseline conditions prior to the start of Phase 2 of the project. Upon substantial completion of the Phase 2 project, baseline and additional step-out sediment sample locations were re-sampled for comparison to the project numerical remedial action objectives (NRAOs) and baseline conditions. Some sample locations exhibited elevated concentrations of contaminants of concern (COCs) compared to baseline conditions and exceeded the NRAOs. The spatial extent of sediments with chemistry in excess of the NRAOs was limited and post-remediation diver surveys did not indicate significant deposits of dredge material or residuals outside of the TRB. Increases in COC concentrations in surface sediment samples outside of the TRB may be attributable to periodic release of suspended sediments from the Phase 2 work area beyond the TRB; however, influx of contaminated sediment from other adjacent areas of the Harbour may also have contributed to the elevated COC concentrations. In order to address the elevated concentrations of COCs observed in post-construction sediment samples, the contractor was required to place a residuals management sand cover in areas with higher concentrations to provide a clean surface at the end of construction. The cover is designed to mix with the underlying surficial sediments over time to maintain the remediation performance criteria and follow-up monitoring is planned to verify this. 

Data from the water quality and sediment chemistry performance monitoring provide evidence that the TRB system was generally very effective in preventing the escape of contaminated particulate matter to the water column and seabed in the previously dredged areas of the EGD waterlot that surround the Phase 2 remediation area. 

 
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Fish Habitat in the Balance: When Does the Remediation Dredging Scale Tip From Net-environmental Benefit to Serious Harm to Fish?
Derek Nishimura, Golder Associates Ltd.

The objective of this presentation is to discuss how the habitat values in Esquimalt Harbour were characterized, efforts made to avoid disruption of high value habitat, mitigation measures that could be applied to minimize changes to fish habitat, and finally, how these factors were brought together in an overall conclusion of whether serious harm to fish would result from remediation activities and facility upgrades and ultimately whether offsetting was needed.

Abstract

The Department of National Defence (DND) is implementing an aquatic contaminated site remediation program in Esquimalt Harbour, as part of a long-term strategy to address sediments that have been contaminated by historical industrial activities in the harbour dating back to the mid-1800s. The project area is currently under the ownership and management of DND and part of the Canadian Forces Base (CFB) Esquimalt. This remediation program is one of the largest being undertaken on the West Coast of Canada, and is being implemented in a phased approach that is initially targeting six areas of higher contaminant concentrations, and for some of the targeted areas coincides with facility upgrades. Longer-term remediation and management of other areas of the harbour will be based on the results of ongoing updates to a human health and ecological risk assessment. Overall, the remediation program is intended to result in a net environment benefit.

Despite the presence of contaminants, the area supports significant environmental resources and the permitting for the remediation project and associated infrastructure upgrades has had to address the habitat protection provisions of the federal Fisheries Act, which has in recent years shifted from an emphasis on productive capacity to productivity. To date, the focus of the Fisheries Act permitting has been for changes to fish habitat related to the facility upgrades rather than for the remediation dredging. 

The shoreline and nearshore areas around Esquimalt Harbour are mostly comprised of hard substrates such as boulders and bedrock, and the seafloor is mostly finer-grained unconsolidated sediments. This substrate gradation determines the habitat values that need to be considered in each remediation zone in terms of quantifying the potential for lost productivity as a result of remediation activities. In the harbour, harder substrates tend to support higher value habitat such as kelp beds and other macroalgae, which are important for species related commercial, recreational and Aboriginal fisheries, as well as protected species such as Northern Abalone (Haliotis kamtschatkana). In addition to being of higher value, these types of habitat also tend to take longer to re-establish once disrupted. Conversely, the softer substrates provide lower habitat value and will recolonize relatively rapidly following dredging. Changes to higher value habitat that takes longer to re-establish has a greater potential to affect productivity and thus a greater potential to result in serious harm to fish as defined by the Fisheries Act and thus a need to provide offsetting to replace the lost productivity.

To support the long-term program of remediation and facility upgrades in Esquimalt Harbour, DND has proactively established a habitat offsetting program that includes a “bank” of fish habitat constructed in advance of activities that might result in serious harm to fish. As each project component is addressed, the productivity loss is quantified and compared to the “credit” available in the bank. In some cases, the type of habitat being affected is different than the habitat in the bank and therefore different “currency conversions” have been applied.

This presentation will discuss how the habitat values in Esquimalt Harbour were characterized, efforts made to avoid disruption of high value habitat, mitigation measures that could be applied to minimize changes to fish habitat, and finally, how these factors were brought together in an overall conclusion of whether serious harm to fish would result from remediation activities and facility upgrades and ultimately whether offsetting was needed. 

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