Reinforcing the shoreline
The Cordova Bay shoreline at Mount Douglas Park has been eroding for many years. Saanich has done a number of projects to try and stabilize it and has had a number of studies done since the 1980’s. The remedial projects worked to some extent, but none were completely successful. The shoreline continues to erode and the bank continues to slip.
In 2000 Thurber Consultants prepared a report [PDF - 13.6 MB] recommending horizontal drilling on the face of the slope to relieve groundwater pressure, bioengineering of the slope to stabilize the soils, and additional rock revetment on the shore to keep the toe from eroding.
Further review of the impact of the proposed rock revetment on the marine environment and habitat led to concerns and a push to consider alternatives.
- Marine Habitat Inventory and Impact Assessment Related to the Proposed Rock Revetment [PDF - 4.3 MB]
- Slope Stabilization Revetment Environmental Impact Assessment: Terrestrial [PDF - 4.2 MB]
As a result of the environmental review and the public consultation, a design concept was developed that was considered to be more sensitive to the marine environment.
The concept involved installing a number of headlands or groins along the beach and backfilling them with sand, all designed to have the material stay within the sphere of the headlands and not move along the beach, while providing energy dissipation for waves as they came ashore. As well, the project still involved drilling horizontal relief wells into the bank for groundwater movement, and implementing bioengineering for slope stabilization.
Saanich Council agreed to the concept. Over the next few years the consultants conducted studies on the wave action and sediment transport in Cordova Bay; did laboratory studies to determine the best material to use for the particular conditions in Cordova Bay and finalized the best layout of the headlands.
The design was completed in 2009 along with cost estimates:
- Shoreline Cliff Protection Drawings [PDF - 5.2 MB]
- Horizontal Drain and Bioremediation Conceptual Design Review and Cost Estimate [PDF - 3.5 MB]
- Mount Douglas Park Shoreline Protection - Design Update [PDF - 17 KB]
Slope Stability Reviews
While the design concepts were being prepared and while the detailed designs were underway, Thurber Engineering was retained to review the stability of the shoreline on an ongoing basis.
Their most recent report [PDF - 3.1 MB] is from May 2016.
As noted in the report, the bank north of Mount Douglas Park is affected similarly to that fronting the park, and Thurber recommended that property owners be advised to seek professional advice regarding the terrain hazard on their individual properties. Similar advice was provided to some property owners in 2014.