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Project Details

Fabric 1

PROPEX Pyramattress
Producer/Manufacturer: Solmax International Inc.
Primary Use: Main Fabric

Fabric 2

Bentoliner GCL
Producer/Manufacturer: Solmax International Inc.
Primary Use: Secondary Fabric

Fabric 3

MIRAFI 160N
Producer/Manufacturer: Solmax International Inc.
Primary Use: Secondary Fabric

Engineer Company 1
McElhanney

Please describe the project specifications

The Town of Comox is located on the eastern coast of Vancouver Island, British Columbia. When a new residential community was planned for the neighborhood of Anderton, a stormwater pond was required for the development. The stormwater pond was planned to be built where an old gravel pit had been located, and the inlet channel at the pond needed to be armored.

Prior to construction, the inlet channel to the pond had a 12.5% longitudinal slope and a 2.20m bottom width with 2H:1V side slopes to the design depth of 1.0m deep, then 2.5H:1V above until daylighting. The subsurface soils were highly erodible compacted sand, and extreme erosion existed from previous rain events.

McElhanney, the project engineer, initially designed a solution using articulated concrete block to armor the channel, but this proved to be a very expensive solution. The project engineer contacted us for an alternative solution that would be more economical and more environmentally friendly.

This was a unique application due to the complex challenge of the highly erodible soil and limited site access. Our erosion control solutions were combined with its geosynthetic clay liners and nonwoven geotextiles to provide a long-term solution. Additionally, the solution had to be submitted and approved by the City of Comox.

The project team reengineered the inlet section to make the hydraulics of the channel compatible with PROPEX Pyramattress in a 100-year storm event. Pyramattress is an engineered mattress system that provides erosion control that resists potential scour and erosion caused by the constant flow of water or high hydraulic stresses. The system utilizes the durability and erosion resistance of PROPEX Pyramat 75 High-Performance Turf Reinforcement Mat (HPTRM) to construct a geosynthetic/soil/rock composite to protection of channel and slopes. Approximately 1,025 y2 (857 m2) of Pyramattress was installed on the bottom and the side slopes of the channel. To provide additional erosion control, 1,580 y2 (1321 m2) Pyramat 75 HPTRM was installed above the Pyramattress on both o the side slopes of the channel.

Due to the extremely erodible soils, BENTOLINER was installed under the Pyramattress system to isolate flows from the erodible soils. BENTOLINER is a geosynthetic clay liner that combines the dimensional stability and increased internal shear strength of reinforced geotextiles with the high swelling capacity and low permeability of sodium bentonite. In applications where increased internal shear strength is required BENTOLINER provides a high sealing effect. On the slopes of the inlet channel, 2,800 y2 (2,341 m2) of Bentoliner was installed.

Finally, MIRAFI 160N was used to wrap the drainage stone around pipes and drains within the design. MIRAFI 160N is a nonwoven geotextile that combines high water flow rates, high soil interaction and durability while providing excellent soil particle retention. Approximately 1,120 y2 (936 m2) was used to provide soil separation, filtration and drainage.

The City approved the solution and it was successfully installed in July 2023.

Selecting the combination of our solutions over articulated concrete block provided a 50% cost savings. Additionally, this solution provided a significant reduction in carbon emissions. We are the first company to verify the carbon footprint of its HPTRM, by an independent, third-party organization. From cradle to grave, Pyramat’s carbon footprint is 2.7 kgCO2e per 1m2 of material. Comparatively, concrete-based alternatives for erosion control, like articulated concrete block, are up to 10 times higher. Pyramat is the primary component in the Pyramattress system. Once installed, Pyramat helps to decrease sedimentation and pollutants and encourage infiltration of water back into the groundwater table. These are two reasons why the EPA has identified HPTRMs like PYRAMAT as a Best Management Practice for improving water quality.

Finally, both Pyramat and Pyramattress are designed to promote vegetation reinforcement, thus providing a more aesthetically pleasing solution.

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