Geotextiles: Installation

Backfill Granular, Utilities and Pipes: Geotextiles

Geotextiles are filter fabrics that can be installed to separate dissimilar soils and prevent the migration of materials. Geotextiles are recommended for installation at the bottom and side limits of the LID feature and should be implemented at the discretion of the engineer.

Construction Steps:

1. Roll out fabric on the flattened sub-grade surface.
2. Provide a minimum overlap of 300 mm between adjacent lengths of geotextile. If the manufacturer specifies a greater overlap, follow the manufacturer’s specification.
3. Secure fabric in place with stakes along the edge of the sub-grade surface and where lengths of fabric overlap.
4. Provide 500 mm of excess at the ends of each length of fabric. Fold excess materiel on top of the infiltration medium/choker course once installed.
5. Provide cuts for trees and shrubs where appropriate.
6. Assess on-site conditions to ensure that the tensile, tear, and puncture strength ratings of the geotextile are suitable for expected structural loads (e.g. traffic). If not properly considered, geotextiles can be adversely impacted by loading from adjacent infrastructure uses.

Key Inspection Points:

• Geotextile is clean and free of damage.
• Geotextile delivered to the site matches the design specifications and is approved by the engineer prior to installation.
• Sufficient overlap is provided between lengths of fabric.
• Geotextiles have been applied as per the manufacturer’s guidelines.
• Structural considerations for geotextiles have been made when applied adjacent to infrastructure and the geotextile can handle expected structural loads.
• Class II geotextiles conform to OPSS 1860.

Mistakes to Avoid:

• Wrinkles in the fabric – follow the manufacturer’s procedure for installation to ensure geotextiles lie smooth on sub-grade.
• Unnecessary application of geotextile – mixing of media is negligible where structural loads are not expected, so geotextile does not need to be applied. Also, geotextiles should not be used where root growth is encouraged to penetrate different layers of media.

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  The shape of the LID feature required the geotextile to be rolled out prior to being laid on the subgrade surface.

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  Excess fabric is draped over the edges of the LID practice, and backfilling with granular is taking place.

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  Footprint with geotextile, granular, and underdrain.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.

The total mass of a pollutant entering a waterbody over a defined time period.

The net amount of something (e.g. chemical, such as phosphorus), calculated as the product of concentration and volume in a given time. Some BMPs significantly reduce loading of pollutants to the environment by reducing volume more so than concentration.

Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

A perforated pipe used to assist the draining of soils.