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In 2012, storms caused extensive surface flooding, damaged homes, vehicles and property and caused sewage backup into basements throughout Tweddle Place. This neighbourhood was identified as a high priority for drainage upgrades.

The upgrades in Tweddle Place will provide the community with a 1:100 year level of flood protection that is consistent with standards in newly developed neighbourhoods.

Project details

Planned uprades for Tweddle Place include storm sewer upgrades, sanitary storage pipes, construction of drainage swales to relieve stormwater trapped in low areas and expansion of the existing dry pond along 91 Street. The sewers will carry stormwater flows to the downstream sewer system and eventually out to the river. When capacity is not available in the downstream system, the stormwater will be temporarily stored in the dry pond.

Two residential lots in low lying areas of the community have been purchased. These lots will be converted to drainage swales that will route stormwater on the ground into the 91 Street dry pond. Since catch basins can become obstructed with leaves and other debris, and pipes can fill up, the surface drainage swales through the 2 empty lots will provide an alternate flow path for stormwater unable to enter the pipe system.

Impacts to residents

Construction of the project is staged over 7 years and will invove open excavation construction methods. The upgraded pipes are very large so residents can expect that the full width of the roadway will be cut open in some areas. During construction, residents will temporarily lose access to their driveways and street parking, and areas adjacent to construction zones may be more congested as street parking shifts to these areas.


Millbourne Flood Mitigation Task Force monthly reports


​2018 ​2019
Construction details

How we'll communicate about construction

During the construction stage, an update of the construction status and planned work for the next season is mailed out each fall. Residents are notified of upcoming construction in their area 1 to 2 months prior to construction beginning through mailouts and door to door visits, and a pre-construction open house is held at least 2 weeks prior to the start of construction each year.

Residents affected directly by construction have an opportunity to ask the contractor construction-specific questions at these events. Prior to the construction, a notice is delivered to residents in the community. Residents should keep this notice handy, as it contains key contact information if you have concerns or questions.

Periodic updates about construction progress will be distributed to directly affected residents. Updates to the community league and North Millbourne Flood Mitigation Task Force are also provided.

What residents can expect

During construction, residents in some areas will lose access to their driveways and street parking, and areas adjacent to construction zones may be more congested as street parking shifts to these areas. The project team works to limit the duration of closures, but wet weather can significantly impact the construction schedule, access and site conditions. Residents with special mobility concerns can contact the project manager to discuss accommodation during construction.

Portion of yard along roadway may be removed: The road right of way typically extends into front yards, sometimes as much as 5 metres. Utilities and services such as cable are located within this right of way. These utilities sometimes have to be exposed for construction work. In cases where large or multiple pipes are being constructed and located deeper in the ground, the excavated trench may need to extend close to a resident’s property line to maintain a safe excavation. The contractor is required to restore any impacted landscaping to pre-construction conditions.

Tree removal: Where construction affects the root zone of private trees, we may approach property owners to remove the affected trees. This is done to avoid burdening owners with long term maintenance issues, because construction impacted roots may cause the tree to weaken and in some cases, die. Permission will be obtained from owners prior to removing any trees. Removed trees will be replaced.

Materials storage on road right of way: Construction contractors will store pipes, materials for filling in the trench and other equipment or supplies necessary for this work along the roadway around the construction site. When spaces are available to store this material off the roadway, they will make use of these spaces. Contractors try to limit the amount of material stored on the roadways, and amounts may vary depending on how quickly the contractor is advancing construction, ground conditions encountered, supplier availability, etc.

Materials storage on private property: Contractors should not be storing materials on or using private property without permission from the property owner. Any concerns related to inappropriate storage of material or use of private property should be directed to EPCOR's project manager or directly to the construction contractor’s site representative.

Impacts to residents

Impacts to utility services: Utilities may need to be disconnected, relocated or temporarily shut down to allow construction to proceed safely or to avoid damage to the utility. The project team will arrange for temporary supply of any affected services. There may be short duration outages associated with connecting the property to these temporary services. The contractor or utility company will notify homeowners of any planned outages at least 24 hours prior to the planned outage.

Muddy site conditions: Wet weather can create muddy and messy conditions at construction sites. The project team and contractor work to keep roadways and sidewalks as clean and safe as possible. However, if you have concerns, please call EPCOR or the contractor contacts provided on your construction notice. EPCOR will work with the contractor to improve the site conditions in these situations.

Living wall

​Thank you for your feedback about the Living Wall demonstration project. Based on positive input from the community, noise monitoring and demonstrated ability of the plant material (willows) to survive Edmonton's climate, we will be moving forward with the living wall on the rest of 91 Street from Mill Woods Road to Whitemud Drive.

Construction of the expanded Tweddle Place dry pond, followed by extension of the wall, will begin in fall 2016.

About the living wall

As a demonstration project, the City of Edmonton is building a three metre tall living wall along a portion of 91 Street just north of Mill Woods Road. It is part of a larger flood mitigation program planned for the Millbourne area. The program will result in the removal of the existing berm along 91 Street from Mill Woods Road to Whitemud Drive to enable expansion of the existing dry ponds on the east side of 91 Street in this section. The berm must be replaced with a suitable sound and visual barrier.

A living wall is an environmentally friendly alternative to walls made out of concrete or other hard materials. The wall is composed of earth, wood and willow shrubs and has proven effective in Europe and eastern Canada and now, Edmonton. The living wall concept aligns with multiple City sustainability objectives, including naturalization, increasing biodiversity, improving air quality and green infrastructure innovation.


​Community consultation and engineering studies began soon after the 2012 flooding, with detailed design beginning in early 2014. Construction of the project is staged over 7 years beginning in 2015. The construction timing is based on available budget for this work, scope that can be completed in 1 season, priority of upgrades, and impacts to the neighbourhood (road closures, pedestrian accommodation, utilities coordination).

Open house

An open house will be held prior to each stage of construction. An invitation to attend the information meeting will be mailed out to the community approximately 2 weeks prior to the date of the open house.

On June 7, 2017, an open house was held for the Tweddle Place Dry Pond Expansion work. The session included a presentation which provided project information and progress.


​How does the pond work?

During normal operation, water in Tweddle Place stormwater pipes flow downstream into the Mill Woods Double Barrel pipe system and the pond will remain dry. However, during large storms, pipes within the community and downstream sewers can fill up. When the pipe system is full, water will back up into the Tweddle Place dry pond. The dry pond will collect overland surface stormwater and store it until capacity is available in the downstream system. When capacity becomes available, the stormwater will drain through catch basins in the bottom of the dry pond into the pipe system.

Why does the berm have to be removed?

The berm is being removed so the dry pond can be expanded to accomodate larger volumes of stormwater that will be directed to the pond. Removal of the berm also ensures that low areas in the community have an unrestricted flow path into the dry pond across the drainage swales that are being constructed.

Why do the trees have to be removed?

Regretfully, trees along the berm have to be removed to allow the berm to be removed. Trees that would be impacted by construction activities will also be removed, This area will be re-landscaped at the end of the dry pond expansion with a mix of native grasses and vegetation, trees and shrubs. Seating areas will also be incorporated into the expanded dry pond, and the existing shared use path will be relocated further east in the pond area. Access to the shared use path will be maintained with openings along the future sound barrier, a living wall.

What is a living wall?

A living wall is a visual and sound barrier that incorporates plant material to form a hedge-like, more natural alternative to traditional sound barriers. It replaces the sound and visual barrier functions of the existing earth berm. A demonstration project of the living wall was built in late 2014 near the Mill Woods Christian School along 91 Street.

The living wall demonstration project seems to be struggling. Why is this, and what is being done to make sure it grows?

The living wall demonstration project was constructed in fall 2014. The intention of the demonstration project was to allow the community to experience this type of wall and to confirm its ability to grow in Edmonton’s climate. In a survey, the majority of people who experienced the wall indicated they were supportive of making it a permanent replacement for the berm. Testing proved it was effective as a noise barrier.

For the demonstration, a temporary water supply was installed to help the wall get established. In the establishment phase of the wall, it is critical for the vegetation of the wall to be well irrigated. In the spring of 2015, the water supply was shut off, depriving the wall of water during a hot, dry spring. This resulted in the death of many of the willow stalks. While some additional willow stalks were planted to compensate for these deaths on the community side of the wall, a large number of willows were not replaced.

During the dry pond expansion, this section of the wall will be augmented with additional plants. Additionally, the full installation will include a piped source of water for the wall. To ensure proper establishment, the contractor will be required to maintain the wall for an extended period.

Will the living wall prevent noise from Whitemud drive and 91 street?

The living wall is a sound barrier, and the effectiveness of its design has been proven with noise monitoring and modelling according to engineering best practices. The wall contains a soil core that is a barrier to sound and functions year round. It also provides other environmental benefits such as cleaning the air, promoting biodiversity and providing wildlife habitat.

What if the construction damages my property?

Occasionally, damage to property or persons may be caused by construction activities. If you believe that you have sustained damage caused by EPCOR or its contractors, you can submit a claim to our adjuster who will investigate and make a recommendation to EPCOR regarding its liability.

What should I do if service is lost during construction?

If you experience an unplanned loss of service related to: