Restoring Coldwater Fish Habitat

Monora Park is a 17-hectare natural park owned by CVC and managed by the Town of Mono. Within Monora Park, Monora Creek was dammed in 1965 to create a pond suitable for recreation including swimming and fishing. Over time, as the pond has filled with silt, it no longer provides a place for swimming and fishing, although it remains a local landmark.

Today, the park acts as an important greenspace for residents with 18 kilometres of walking, biking and cross-country ski trails, a picnic shelter, gazebo, open playing field, and Monora Pavilion–a venue for public and private events including weddings and conferences. 

The Dam Structure

The dam consists of an embankment (or berm) to hold back water. This creates the pond and a morning glory-style spillway structure that regulates the water level and drains through a corrugated steel pipe culvert to the downstream creek channel. The integrity and structure of the culvert has been in decline. It requires we take action as the safety risk and liability of the dam failing increases over time. 

We have evaluated different options for the Monora dam and associated pond, taking into consideration the goals of improving the natural environment of Monora Creek as well as safety, social, recreational and economic values. The preferred option that met all these objectives is to decommission the dam. This will allow a natural channel to form and reconnect Monora Creek with enhanced restoration of the pond basin.

Water Temperature Restored

CVC has decided to move forward with the preferred option and began lowering the pond in May 2022 and completing detailed design and permitting to decommissioning the dam and pond.

Data collected over the past several months since lowering the water has revealed that a more natural thermal profile has been restored. This means that sensitive coldwater species, like brook trout, can inhabit this stretch of Monora Creek for the first time since the creek was dammed.

The Restoration Process

There are several stages to restoring coldwater fish habitat in Monora Creek.

Set Objectives

Objectives for the project are:

  • Remove the risk to public safety and liability associated with the deteriorating dam
  • Remove the environmental impacts of the dam including improving stream temperature in coldwater fish habitat and removing the barrier to fish passage for sensitive brook trout population
  • Restore stream and wetland habitat in pond basin
  • Maintain and enhance trail connectivity for recreational purposes

Evaluate Mitigation Options

We evaluated four mitigation options using criteria to meet project objectives.

Option 1: Restore Monora Creek with wetlands – complete dam removal

  • Removes entire berm and spillway
  • Improves Monora Creek water temperature by removing warmwater pond
  • Restores fish passage by reconnecting upstream and downstream
  • Maintains wetland habitat

Option 2: Restore Monora Creek with wetlands – partial dam removal

  • Removes portions of berm only and entire control structure
  • Improves Monora Creek water temperature by removing warmwater pond
  • Restores fish passage by reconnecting upstream and downstream
  • Maintains wetland habitat

Option 3: Construct an artificial stream around the pond – rebuild dam

  • Rebuild dam
  • Restores fish passage by reconnecting upstream and downstream
  • Continued and sustained harm to environment
  • Continued long term liability and ongoing life cycle costs
  • Costly

Option 4: Rebuild dam

  • Continued and sustained harm to environment
  • Continued long term liability and ongoing life cycle costs
  • Costly

Preferred Mitigation Option:

Options one and two that would remove all or part of the dam and berm and restore the stream and wetland habitat ranked very closely in the assessment. The permitting and detailed design process will inform how much regrading will be required to construct an appropriately sized channel and stream crossing.

The preferred option to remove the dam and pond will move into detailed design and permitting in 2023 in consultation with provincial agencies, the public and stakeholders. The input we received will help inform the final design that advances to construction. 

The project’s construction is scheduled to be completed in 2024, June 15 to September 30.

The project’s construction is scheduled to be completed in 2024, June 15 to September 30.

Frequently Asked Questions

As the dam was built in 1965, it’s now at the end of its life cycle.

The dam does not meet current dam safety requirements. To maintain a pond would require significant cost and additional environmental assessment. We did evaluate options for keeping the pond (i.e., bypass channel) but maintaining a pond would cause continued harm to Monora Creek and the sensitive brook trout community that is at risk. Some of the pond wetland functions such as the marsh habitat will be incorporated into the design.

The benefits of removing the dam include contributing to CVC’s and the Town of Mono’s environmental and climate change goals, improving habitat and making the water cooler for sensitive and disappearing book trout. Removing the dam will also remove a barrier to fish movement by connecting Monora Creek upstream and downstream of the dam. Additionally, it will eliminate the safety risk and liability surrounding the aging structure.

Unfortunately, there will be some disruption to park access at this location during construction. We are hopeful that construction can be completed in less than three months. We are working with the Town of Mono staff to minimize construction disruptions. We do anticipate that trail access will be available at existing alternate access locations.

CVC staff are visiting the site regularly to make sure impacts to wildlife are avoided or minimized.

We’re minimizing impacts to wildlife by using best management practices. One of these practices included lowering the pond in spring to allow wildlife to seek refuge before winter. We will also look at construction timing windows to avoid disturbing wildlife at critical periods, conducting wildlife rescues as needed and taking steps to control sediment build up and prevent erosion.

We have collected extensive baseline data about the plants and animals using Monora Pond to incorporate these considerations into the detailed design and construction planning. The habitat that we restore will continue to provide habitat for the plants and animals that currently live there. The detailed design will maintain marsh habitat and improve stream habitat. 

There is a provincial exemption from the Ministry of the Environment Climate Change and Parks under Ontario Regulation 334 to decommission dams built prior to the Environmental Assessment Act coming into effect in 1976. Monora dam was built in 1965 making it eligible for this exemption for decommissioning.

Monora dam was also built for recreational purposes and does not serve a flooding or erosion control function. The fish and wildlife management component of the project also meets exemption criteria for decommissioning under the Conservation Ontario Class Environmental Assessment process. CVC has adopted an EA like process in its feasibility study to assess a variety of options for its mitigation.

Rebuilding the dam requires an EA.

The feasibility study establishes objectives for the project and evaluation criteria to assess different options. The study concluded the preferred option that best achieves the project objectives related to public safety, environmental impacts and trail connectivity is to decommission the dam.

The final layout and amenities will be explored through detailed design and permitting in consultation with the public, the Town of Mono and stakeholders. Based on the preferred option under consideration, the site will have a natural cascading stream, with park elements and nature designed to function with the surroundings and park use. The river channel will be restored, and some wetlands will be established within the existing pond basin. Initially, there may be some exposed muddy areas, but they will quickly grow vegetative cover and will be planted with trees and shrubs.

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