Britannia Retaining Wall Rehabilitation, Phase 2

The Britannia retaining wall was originally built in the early 20th century to support a railway which ran partly along the Ottawa River.  It currently supports a pathway corridor that is part of the National Capital Commission's (NCC) multi-use pathway network.  The retaining wall and associated culverts have historically provided informal flood protection to the adjacent residential neighborhood from fluctuations in the water level of the Ottawa River.  However, the City of Ottawa is formally responsible for providing flood protection to the adjacent residential neighborhood.  The wall now requires rehabilitation, as it is showing signs of critical failure.


The retaining wall is built from stones of varying sizes and types, with unusually large joints.  There is no geotextile fabric behind the masonry wall, and erosion of smaller materials has occurredAt certain wall sections, mortar and concrete coping have disintegrated or are missing due to aging.  Phase 1 of the project rehabilitated certain wall sections (approximately 240 m in length).  However, some sections in poor condition that were assessed and approved under the Canadian Environmental Assessment Act, 2012, and could not be completed in 2019 and 2020 due to lack of funding, will be completed in 2022 - 2023 under Phase 2.  This notice of intent to make a determination under the Impact Assessment Act (IAA) is exclusively for Phase 2 of the Britannia retaining wall rehabilitation project, to be undertaken in 2022 - 2023.


The specific rehabilitation work to be undertaken on the wall sections will be determined after an assessment of the deterioration of the various wall sections.   The following are the options to rehabilitate the deteriorated wall sections:


  • re-pointing/re-mortaring the masonry joints
  • re-pointing/re-mortaring the masonry joints with some stone replacement
  • dismantling the masonry wall and re-building the wall to a higher elevation
  • dismantling small remnants of masonry wall and re-building the wall to a higher elevation


The retaining wall sections to be rehabilitated are within the Ottawa River's 100-year floodplain.


The project will consist of four stages, which are outlined below, along with a list of construction work to be undertaken during each stage.


  1. Site preparation

· Creation of a construction access point and staging area
· Grubbing and removal of vegetation, as required

· Installation of erosion and sediment control measures
· Installation of wildlife exclusion measures
· Installation of pedestrian and traffic exclusion measures


  1. Construction

· Operation of heavy machinery
· Excavation and movement of earth
· Dismantling/demolition of wall sections
· Construction of new foundation
· Re-building of wall sections
· Stone replacement
· Re-pointing/re-mortaring of masonry joints


  1. Post-construction and reclamation

· Revegetation of disturbed areas
· Removal of erosion/sediment control measures
· Removal of wildlife exclusion measures
· Removal of pedestrian and traffic exclusion measures
· Waste disposal
· Dismantling site access and staging area
· Reinstating of pedestrian access to pathway



· General maintenance of trails, staging area and the construction site, as required.


The new wall sections will consist of precast modular concrete blocks supplied by Redi-Rock with an uncolored (regular concrete grey) "Ledgestone" block texture that resembles the original rubble stonewall.  To address high water levels, such as those that occurred during the flood events in 2017 and 2019 when water flowed over the top of the wall, the new rehabilitated wall will be higher than the existing wall.


Throughout 2020, the site was in a state of construction. The project will continue to be coordinated with stakeholders identified throughout the project implementation phase.  This includes federal coordination with the Canadian Wildlife Service of Environment and Climate Change Canada.  The former will issue a permit under the Species at Risk Act to remove six Butternut trees and the latter will make a determination under the IAA to enable Phase 2 of the Britannia retaining wall rehabilitation project.


Latest update

Notice of Determination

Ottawa - September 28, 2022 – The National Capital Commission and Environment and Climate Change Canada have determined that the proposed Britannia Retaining Wall Rehabilitation, Phase 2 project is not likely to cause significant adverse environmental effects.



National Capital Commission
Environmental Assessment
40 Elgin Street
Ottawa, Ontario K1P 5A8

  • Location

    • Ottawa (Ontario)
  • Nature of Activity

    • Other, not otherwise specified
  • Assessment Status

  • Start Date

  • Proponent

    The National Capital Commission
  • Authorities

    • Environment and Climate Change Canada
    • National Capital Commission
  • Assessment Type

    Project on federal lands
  • Reference Number


This map is for illustrative purposes. The markers represent the approximate locations based on available data. More than one marker may be identified for a given assessment.


Nearby assessments

...within 200 kilometres
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