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West Etobicoke Creek South of Britannia Road East Erosion Control Project

Toronto and Region Conservation Authority (TRCA) is preparing to undertake remedial erosion control and slope stabilization works along a localized section of the West Etobicoke Creek, South of Britannia Road East in the City of Mississauga, where slope instability and ongoing erosion are creating a risk to public safety and infrastructure.

 

Project Background

In 2007, TRCA erosion monitoring staff reported concerns of slope instability along the south bank and ravine wall of Etobicoke Creek immediately downstream of the Britannia Road East bridge, near the southwest corner of the Lester B. Pearson International Airport.  

Follow-up site inspections conducted by TRCA staff identified a significant erosion scar along the river bank immediately downstream of the Britannia Road East bridge (Erosion Site #1), and a section of river bank further downstream that has undergone erosion, leading to a series of progressive rotational failures up the valley slope (Erosion Site #2).

In 2008 TRCA retained the professional engineering firm Jacques Whitford Environment Ltd. to complete a geomorphic and slope stability assessment. The objective of the assessment was to examine the cause(s) and effect(s) of the riverbank erosion and slope instability based on existing and acquired geotechnical and topographical data. Specifically, the associated hazards in terms of property loss and the risk to existing structures and public safety were assessed and preliminary remedial options appropriate to the location were identified.

The final report submitted by Jacques Whitford Environment Ltd. to TRCA in April 2009 determined that the riverbank Erosion Site #1 does not currently threaten property or infrastructure. However, a preferred approach for bank stabilization was suggested by the consultant if TRCA chose to pursue such works. Erosion Site #2 was deemed to pose a threat to public safety and private property along the adjacent table lands. Jacques Whitford Environment Ltd. recommended slope restoration and channel bank stabilization works in combination with tableland drainage to mitigate the risk of slope failure.

Based on these findings, TRCA undertook a Class Environmental Assessment (Class EA) to identify a remedial solution for the West Etobicoke Creek South of Britannia Road East Erosion Control Site Project. The study proposal received approval to proceed at Authority Meeting #7/10 held on September 17, 2010, and a Notice of Intent was published in the January 20, 2011 and January 21, 2011 Editions of the Mississauga News to inform the public that a Class EA was commenced for the design and implementation of remedial works for the West Etobicoke Creek South of Britannia Road East Erosion Control Project.  TRCA also retained W.F. Baird and Associates to assist with geomorphic, geotechnical and engineering consultant services in support of the Class EA. 

 

Project Purpose

The purpose of the West Etobicoke Creek South of Britannia Road East Erosion Control Project (the Project) is to reduce the risk to public safety and infrastructure by providing long-term, low maintenance, protection against erosion and slope instability, which is compatible within the surrounding physical, biological, social, and cultural environment.

Given that the lands currently at risk are in private-ownership, and have been utilized for their on-going operations for years, preventative measures were deemed insufficient and impractical to address the observed risk. Instead, a risk-managed approach for the remedial works will be required to address the observed risk due to erosion.

 

Planning Mechanism for the Undertaking

TRCA must conduct its remedial flood and erosion control projects in accordance with the Environmental Assessment Act (EAA). Recognizing that common elements exist in addressing flood and erosion problems, a more efficient approach to environmental assessment was developed by Conservation Ontario for all conservation authorities known as the Class Environmental Assessment for Remedial Flood and Erosion Control Projects (Class EA). The Class EA approach is considered a suitable means for the planning of remedial flood and erosion control projects because it provides a consistent, streamlined process that ensures compliance with Environmental Assessment Act (EAA) requirements.

TRCA submitted the following Project Plan in support of the West Etobicoke Creek South of Britannia Road East Erosion Control Project for approval by the Ministry of the Environment under subsection 7(1) of the Environmental Assessment Act (EAA) on October 21, 2011.

 

The Project

As described in the Project Plan, a combination of vegetated rip-rap, stream barbs, and valley slope re-grade and drainage improvements were identified as the preferred alternative. These features are proposed for the right bank, with minor bank re-shaping proposed for the left bank to maintain channel width.

The stream barb structures are designed to be mostly emergent at base flow and submergent at bankfull and higher flows. The primary purpose of the stream barbs is to realign the main river flows away from the outer channel bank and promote sediment deposition along the outer bank upstream of the barbs. Additionally, the stream barbs may improve aquatic habitat conditions through the creation of scour pools, backwater refuge areas, etc. in the vicinity of the barb structures.

 

Public and Agency Consultation

The Class EA process provides that all views respecting a proposed remedial flood or erosion control project be taken into consideration during the planning and design of remedial flood and erosion control projects.

As part of Class EA process, a project contact list comprised of aboriginal communities, local community organizations, government agencies, and interested stakeholders was developed. In addition to keeping the contact list apprised of the Project through notices and project updates; consultation meetings were held with interested groups, agencies, and stakeholders, to obtain feedback on the evaluation of alternative options in determining the preferred remedial measure, as well as to address any concerns raised regarding the proposed works.

A Notice of Filing has been published in the October 21, 2011 edition of the Mississauga News to advise the public that the preferred measure of erosion control and slope stabilization has been identified, and that the Project Plan has been placed on public record for thirty (30) calendar days commencing on October 21, 2011.

Comments regarding the proposed works must be submitted in writing, or by email, to Kenneth Dion, Senior Project Manager, by November 20, 2011:

Kenneth Dion, Senior Project Manager
70 Canuck Avenue
Downsview, ON  M3K 2C5
Email: kdion@trca.on.ca

Subject to comments received as a result of this study and the receipt of necessary approvals and funding, TRCA intends to proceed with the construction of this project. If any individual feels that serious environmental concerns remain unresolved after consulting with TRCA staff, it is their right to request that the project be subject to a Part II order by the Minister of the Environment. Part II Order requests must be received by the Minister, with a copy to TRCA, at the following address by November 20, 2011:

Minister of the Environment
135 St. Clair Avenue West, 12th Floor
Toronto, ON  M4V 1P5