Erosion and Sediment Control

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Overview

Erosion and sediment controls (ESC) are technologies, practices and procedures that are applied to prevent the release of sediment from construction sites. Rapid urban expansion and associated construction activities are a significant source of stress to the natural environment. As construction processes involve the removal of vegetation and de-stabilization of soils, they can accelerate natural processes of erosion and sedimentation, mobilizing more sediment and associated contaminants that can ultimately end up in downstream receiving water systems. Erosion and Sediment Control (ESC) measures are essential to help reduce these sediment loads from active construction sites and protect downstream aquatic habitats from becoming impaired.

Effective ESC starts before topsoil stripping begins. This flow chart shows the ESC process from construction project start to finish. Scroll through the wiki to read about each step of the process.

Inadequate ESC during construction can cause:

• sediment-laden runoff to enter downstream and adjacent natural features, including streams, lakes, wetlands and woodlots;
• deposition of sediment on adjacent private property and roadways;
• clogging of onsite stormwater management systems and LIDs;
• expensive cleanup and restoration costs;
• delays or stop-work orders; and
• fines from regulatory agencies.

Implementing effective ESC practices throughout all stages of construction is essential to sustainable urban growth and ensuring regulatory compliance. The Toronto and Region Conservation Authority, through STEP, published the Erosion and Sediment Control Guide for Urban Construction in 2019. This wiki page summarizes key content from the guide and provides additional resources; however, readers should consult the full guide for comprehensive information.

Erosion risk assessments (ERA)

To manage the potential negative impacts of construction activities in the absence of effective ESC measures, Erosion Risk Assessments (ERAs) are conducted to guide the selection and placement of appropriate ESC practices on site. ERAs are recommended when:

• the extent of land disturbance is greater than 10 ha and duration is longer than 30 days, or
• construction activities are planned in or near natural water features, or
• the site drains to species at risk (SAR) habitat

The hybrid qualitative ERA approach is recommended in the above situations with the exception of instances where local regulatory agencies require a different approach. The hybrid qualitative ERA approach estimates erosion risk by dividing a site into areas based on soil, slope, and ground cover, then rating each area as low, moderate, or high erosion risk (link erosion potential subsection) to help choose the right erosion control practices for each stage of construction.

ESC plan design

An ESC plan should be created based on a given site’s ERA, with more controls used in the higher risk areas. An ESC plan should be designed for each stage of construction:

1. Topsoil stripping, and re-stabilization
2. Servicing
3. Building construction
4. Final stabilization/rehabilitation and ESC decommissioning

Types of ESC

• Erosion controls prevent exposed soils from being entrained by water or wind. Practices that prevent erosion are the most effective BMPs because they address sediment at its source.
• Sediment controls address the removal of sediment suspended in stormwater (reactive) through settling (link sedimentation page) and filtration (link filtration page).

The most effective way to apply ESC is to use a multi-barrier approach, which involves the installation of both types of controls in series, to create a resilient system capable of protecting the natural environment from sediment impacts. In a multi-barrier system there is redundancy so that if one control fails, there are still others in place to safeguard downstream features. Selecting the appropriate BMPs for each project stage requires an understanding of BMP function, intended use, expected performance, and maintenance required.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.

Deposition of material of varying size, both mineral and organic away from its site of origin by the action of water, wind, gravity or ice.

Settling-out or deposition of particulate matter suspended in runoff.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Land owned by private individuals or companies.

Soil particles with a diameter less than 0.050 mm.

Sustainable Technologies Evaluation Program

Includes the protection of soil from dislocation by water, wind or other agents.

The technique of removing pollutants from runoff as it infiltrates through the soil.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.