Saint-Édouard-De-Kent Containment Cell
Location: Saint-Édouard-De-Kent, New Brunswick
Client: Public Services and Procurement Canada/ DFO SCH
Timeframe: 2021-2022
Key Staff: Greg MacDonald, Stephen O’Brien, Vince Goreham, Nick Thibodeau
Project Description
Due to environmental requirements, a new containment cell for dredge spoils was needed at the Saint-Édouard-de-Kent Harbour in Kent County, New Brunswick. The existing containment cell was no longer suitable, requiring reconstruction with proper depth, elevation, liner, crushed sandstone and riprap. The reconstruction of the cell also had to be completed within the same footprint. Public Services and Procurement and the Department of Fisheries and Oceans, Small Craft Harbours, retained Harbourside Engineering for this project in 2021.
Harbourside’s Role
Harbourside Engineering Consultants first completed a site visit to inspect the existing cell. The initial work also included a topographic survey of the site, a geotechnical investigation inclusive of test pits, collection of soils samples, and the development of a tender package to replace the existing containment cell.
Existing dredge spoils had to be trucked and then disposed at a new facility until the completion of the new containment cell. A new permanent perimeter berm of crushed sandstone lined with rip rap was built to increase the cell’s total capacity and improve the cell’s ability to filter and drain water from cutter suction dredge operations.
The project was designed by Harbourside through a contract with DFO Small Craft Harbours and the design and construction management were completed by Public Services and Procurement Canada (PSPC).
Engineering Consultants
For this project, Harbourside was engaged as the prime consultant to complete the design of the containment cell reconstruction at the Saint-Édouard-de-Kent Harbour. Our scope of services for this project included pre-design services involving a field geotechnical investigation by means of soil test pits and testing the existing dredge spoils in the cell. A geotechnical report was developed based on the field and laboratory test results. In addition, a berm stability analysis for the new berm was completed which set the maximum slopes of the crushed sandstone and rip rap berm. Harbourside Engineering also coordinated a topographic survey of the existing facility and determined safe clearances from utilities for construction.
Engineering Design
Next, a conceptual design of the containment cell was engineered, which included the removal of existing dredge spoils in the cell and reconstruction of the cell to increase its storage capacity. This would have the added benefit of improving filtration and drainage of disposed material. The key part of this process was engineering a Civil 3D model which produced more accurate cut and fill quantities for all materials. In addition, it allowed us to estimate the impact of raising and lowering the height of the berm and rounding off the top of the cell. Upon reviewing the potential cell geometries, we presented these conceptual designs to PSPC and DFO-SCH.
Next, we completed the detailed design of the containment cell. Detailed engineering design included the development and review of the construction documents, such as drawings, specifications, schedule, and capital cost estimates. This was done at the 99% and 100% completion of the tender package. Part of the detailed design phase also included reviewing the constructability of the proposed containment cell with the Harbourside Geotechnical division. Design review meetings with the client were completed throughout the project in order to review the construction documents.
Tender and Construction Phase
Throughout the tender and construction phase, Harbourside provided support for the PSPC project manager by answering technical queries. As part of this project, Harbourside was involved in supporting DFO-SCH with their environmental submissions to obtain the environmental permits. Harbourside collected soil samples which DFO used to request these permits. In addition, Harbourside developed environmental impact drawings which outlined the existing conditions and new work that was used as part of the environmental review process.
This project was completed in March 2022.
Unique Challenges
One challenge with this project was dealing with environmental concern of removing and disposing of contaminated dredge spoils both offsite and within the cell. To mitigate these concerns, we provided clear requirements for disposal of existing and new dredge material. This was clearly outline within the project to ensure compliance with the provincial and federal regulations. Another challenge was ensuring slope stability of the containment cell berm while minimizing its overall footprint. During dredging operations, the cell fills with water which can lead to saturation of the perimeter berm and potential instability. By identifying the potential risk and impact of slope instability early in the design phase, we were able to work with DFO SCH to maximize the containment cell volume while mitigating the impact of this risk. This helped ensure we met DFO SCH’s project goals of maximizing the cell’s containment volume.
Social Impact
Routine dredging is essential for maintaining boat launches, docking sites and port facilities. This, however, can negatively impact the environment if not done correctly, and if dredge materials are not properly contained. Proper maintenance and usage of the containment cell at Saint-Édouard-de-Kent Harbour will help to preserve the harbour’s health and longevity. By preventing contaminants from leeching back into the water column, the new containment cell will play a vital role in protecting the environment, and local fish populations.
