In 1997 the residence of Winnipeg experienced the “Flood of the Century” due to Red River swelling as a result of abundant snowfall and extreme temperatures that spring. Winnipeg was tasked with finding a solution to provide permanent flood protection for the residential areas along the riverbank and Kilkenny Drive North Community was one such area. A segmental retaining wall design that created a dike - walls on two sides - was chosen to provide flood protection with a pleasing aesthetic while preserving the existing trees and minimizing the environmental impact.

The design by J. Bert Smith of KGS Group, consisted of terraced walls, access ramps and landscaping as a way to maximize the useable back yards while still providing an appealing visual. The riverbank walls incorporated free draining granular zones for stability, while the yard drainage was regulated with gate valves, culverts, watertight caps and clay plugs to keep the flood waters from impacting the residents.

Check out the full case study here or on our website.

We’ve all dealt with managing water after a retaining wall has been built and we have covered this topic in multiple places such as Best Practices and our Retaining Wall Tech Sheets. How though, do you handle water during the construction? Have you ever had a project delayed due to water being in your work area? Put together a water management plan so your projects will not be affected by inclement weather and the crews will be able to complete their work on time.

Check out the Allan Block Commercial Installation Manual for tips on what should be accounted for as the wall designer.

• Identify Concentrated Sources of Water, i.e. irrigation systems, parking lots, etc.
• Site soils
• Grading at top and toe of wall

Identifying potential sources of water is important; especially if they will be concentrated by surfaces such as parking lots or even downspouts and other stormwater capture systems. These can deliver large amounts of water during a rain event and temporary berms may be needed to direct water away from the construction site.

Additionally, intimate knowledge of the soils is required to achieve the design level of compaction. Along that line, the type of soil you are working with may hold water longer, and delay the restart to construction. Consider covering the work area to maintain relatively dry conditions in the construction area to limit delays due to soil saturation.

Finally, temporary grading both at the top and toe of the wall is important to provide a path for water to move away from the construction area. Surface runoff must be diverted so it does not drain over the top of the cut and into the work zone, either through temporary berms or surface drainage swales.

If you have further questions about water management during the wall construction or want to ask a question specific to your project, please contact our engineering department at engineering@allanblock.com or 800-899-5309 x3.

Did you know that Segmental Retaining Walls can be used for applications where water will always be present? Allan Block has a wealth of literature that cover the additional considerations that should be taken when working on these types of projects. Of the considerations noted in Allan Block’s published Best Practices for Retaining Wall Design document , we are going to focus our Hot Topic discussion on embankment protection fabric.

We often get this question and decided we should address why embankment protection fabric should be used for water applications. First let’s address what specifications the fabric needs to meet. Table 1 to the right provides minimum specifications for strength and permeability. We can see that the fabric’s opening size and permeability are small/low, which creates an effective barrier between the infill and existing site soils.

With water applications Allan Block recommends removing existing site soils from the reinforced area and extending the wall rock used in the cores of the blocks to the depth of the geogrid reinforcement. This provides a quick drainage path for water getting into the area behind the wall facing due to the lack of fine particles. We want to prevent the existing site soils from migrating into this area and clogging the wall rock by using embankment protection fabric. Wrap the fabric both under the infill mass and up the back of the reinforced area to a height 12” taller than the predetermined high-water level as shown in the cross section to the left.

For more information on using embankment protection fabric in water-based retaining wall applications please contact our engineering department at engineering@allanblock.com or 800-899-5309 x3.