Questions & Answers

Trent-Severn Waterway National Historic Site

Project Details

Q. What does the dam construction entail?

A. The Scotts Mills Dam at Lock 19 is being fully replaced with a new dam that respects the historic look of the site and has a life expectancy of more than 80 years. The new dam will optimize hydraulic capacity, increase the safety of water management operations, and be constructed in a way that allows improved access for maintenance activities. In addition, the project will be the first step in creating a more public friendly lock site, with pedestrian access onto the dam itself restored.

Q. Is the Scotts Mills Dam an important dam?

A. The Scotts Mills Dam at Lock 19 plays an important role in the City of Peterborough, and is an integral part of the Trent-Severn system. The dam at Lock 19 is one link in a chain of dams across Ontario that help Parks Canada to manage water, achieving a variety of objectives including navigation, mitigation of flooding, and the protection of the environment. Within Peterborough, the dam helps to regulate upstream and downstream water levels, including Little Lake. A role of this dam and others is significant on the function of the Trent-Severn Waterway system and consequently the waterside economy of Peterborough, and the quality of life that Peterborough citizens enjoy.

Q. Why is the Scotts Mills Dam being replaced?

A. Engineering inspections had identified the declining condition of the Scotts Mills Dam structure. Scouring at the base of the dam due to the undertow effect had worked to undermine the dam’s structural integrity, and concrete strength inspections showed deterioration beyond what was deemed acceptable. While the dam as it stood did not pose an imminent risk to public safety, these factors indicated that it had neared the end of its useful life, and a replacement project was initiated.

Q. Where can I find updates about the project?

A. Information about this or any ongoing, major works along the Trent-Severn Waterway can be found at www.pc.gc.ca/tswInfrastucture. To receive updates about projects in your area by e-mail, subscribe by reaching out to pc.trentsevern.pc@canada.ca. Or, follow on Twitter or Facebook @trentsevernnhs.

Impact on Residents

Q. The construction project has had a big impact on the lives of residents in the neighbourhood. What has Parks Canada done in consideration of its neighbours?

A. The dam’s location in the middle of an urban area makes construction very complex and logistically challenging. Parks Canada and our partners at Public Service and Procurement Canada have made every effort to plan a project that reduces impact on the neighbourhood, while balancing the varied risks involved in not completing work in a timely manner. Parks Canada’s efforts to reduce impact on the community have included:

  • Engaging with local schools early on in the project to ensure that the impact of construction on traveling student’s parents will be reduced.
  • Planning a construction traffic route that runs in one direction only to reduce the impact on traffic, and ensuring that flag staff are managing sidewalks around the construction site itself.
  • Providing ongoing construction updates to residents, and engaging on a regular basis in an effort to reduce impacts like noise and lighting.
  • Encouraging the contractor to expedite work and reduce the length of the project; for example, by preparing for subsequent phases concurrent with construction of the new dam.
  • In 2020, switching to a different type of piling system in an effort to reduce both noise and time.
  • Offering pre-construction surveys of homes to residents residing within 100m of the construction site.
  • Placing vibration and noise monitors at the site, and monitoring data based on industry best-practices.
  • Ensuring the installation of hording at the site to reduce construction noise.
Q. What are the hours of work at the construction site?

A. For the first two years of the project, contractors were instructed to work within the hours of 6 a.m. to 11 p.m., inclusive of weekends, with a variety of noise levels allowed at different times. In 2021, Parks Canada allowed the contractor to add an extra shift, for the purpose of reducing schedule slippage due to unforeseen circumstances. This resulted in an extension of work hours of the following:

Monday – Saturday

5 a.m. to 7 a.m. - activities generating non-heavy construction noise only

7 a.m. to 9 p.m. – heavy noise generating activities

9 p.m. to 2 a.m. - activities generating non-heavy construction noise only

Sunday

5 a.m. to 7 a.m. - activities generating non-heavy construction noise only

9 a.m. to 9 p.m. – heavy noise generating activities

9 p.m. to 2 a.m. - activities generating non-heavy construction noise only

    Typical construction activities that may be executed within the non-heavy noise generating work period:

  • General carpentry, including the use of handsaws and hammering
  • General craning, including formwork placement and fueling
  • General site cleaning, cleanup, and organization
  • Rebar placement
  • Concrete finishing and parging



    Construction activities that will not be executed within the non-heavy noise generating work period:

  • Installation of piles
  • Use of machinery or vehicles equipped with backup alarms
  • Demolition, excavation
  • Loading, hauling, and placement of rip rap or concrete
  • Use of air compressors
  • Drilling and bush hammering



The construction hours of the project have ensured that the project can be completed within 2.5 to 3 years as opposed to a longer period of time, balancing both the impact on residents and the project risks.

Q. Why doesn’t the contractor have to work within the municipal noise bylaw?

A. Significant thought was given to the project’s schedule and hours of work during its planning, taking into consideration community impact, as well as the necessity of the structure and the complicated nature of its replacement. Municipal bylaws state “Construction noise within 500 feet of an occupied dwelling is limited to between the hours of 7 A.M. to 9 P.M. daily, or noon to 9 P.M. Sundays”. While Parks Canada is not required to adhere to municipal bylaws for construction noise, contractors on other Parks Canada projects on the Trent-Severn and its reservoirs have been instructed to adhere to local bylaws and provincial regulations in principle.

Parks Canada has, throughout the project thus far, noted the community’s concerns regarding the hours of work at the site. Though Parks Canada originally provided guidance allowing the contractor to work outside of the municipal bylaws, the tender for the work was adjusted to specify that activities generating heavy construction noise will fall within the hours specified in the Municipal By-law pertaining to construction noise. Additional, less noise generating activities may continue beyond these hours.

This is with two exceptions, noting that the hours of work have an impact on the ability to deliver the project on time and on budget: 1) allow construction noise generating activities as early as 9:00 A.M. on Sundays, 2) the hours for noise generating activities may change if required, to allow the project to meet the established schedule.

Q. How is Parks Canada managing water while the new dam is being constructed?

A. The replacement of the dam at Lock 19 is easily one of the most complex projects on the Trent-Severn Waterway as a part of this program of work. It is imperative that Parks Canada maintain an ability to manage water through the dam during construction so that we can continue to mitigate upstream and downstream flood risk; including within the City of Peterborough itself, as there could be impacts to the outflows of the storm sewer system and Jackson Creek. For this reason, the dam is being constructed in phases, allowing water to pass through while construction continues. In addition, residents may see reduced work at the construction site during some spring and summer months. This is both to accommodate fish spawning timelines and to maximize flow capacity during the spring melt.

Project Delays

Q. Parks Canada notified residents of the project in 2016. Why did it taken so long to progress to construction?

A. Parks Canada completed significant preliminary assessment to ensure the most appropriate way forward for both the design of the new dam and the implementation of its construction. This included examining various alternative dam styles to optimize hydraulic capacity, and completing investigations that provide the topography of the bed of the river, the depth of bedrock, and information about existing soil and concrete conditions. Significant environmental analysis has included three years of fish spawning and habitat surveys resulting in the completion of improved and expanded fish spawning habitat downstream for walleye and other fish species.

Q. What has the contractor done to reduce delays that have occurred at the project to replace the Scotts Mills Dam?

A. In the initial phase of the project, the contractor faced delays as they adjusted the means and methods of their work to better suit the site conditions. For instance, a change to H-piles from O-piles in the construction of the cofferdam increased the installation rate significantly once the change was made.

Although the contractor and construction manager worked to shift construction methods and project phasing to re-plan the project in a way that would reduce schedule slippage, some unavoidable delays have occurred.

Water Management

Q. How does Parks Canada manage water while a new dam is being constructed?

A. The replacement of the dam at Lock 19 is easily one of the most complex projects on the Trent-Severn Waterway as a part of this program of work. It is imperative that Parks Canada maintain an ability to manage water through the dam during construction so that we can continue to mitigate upstream and downstream flood risk; including within the City of Peterborough itself, as there could be impacts to the outflows of the storm sewer system and Jackson Creek. For this reason, the dam is being constructed in phases, allowing water to pass through while construction continues. In addition, residents have noticed reduced work at the construction site during the spring and into the summer; this is both to accommodate fish spawning timelines and to maximize flow capacity during the spring melt.

Q. Will the new dam alleviate flooding downstream at Driscoll’s Shores?

A. While the new Scotts Mills Dam has been designed to maximize flow capacity and reduce leakage, the Otonabee River in the area of Driscoll’s Shores represents a bottleneck in the system created by the river’s natural shape and topography. This stretch of river can’t always pass the volume of water required. Driscoll’s Shores is most at risk of flooding during winter melts when there are periods of both cold temperatures, and heavy flows due to upstream volumes of water. This combination of factors leads to the formation of frazil ice, which are ice particles or slush in the water that slow or block the flow of water, exacerbating the narrowing of the Otonabee River through which water must pass.

Development

Q. Will a hydro generating station be built at the site?

A. Hydro development is not included as a part of this project. As previous communication has stated, Parks Canada was in receipt of an application for hydro development as a separate and future initiative. Renewable energy changes at the Provincial level in years past rendered that application no longer active.

Q. Parks Canada purchased homes on River Road South and then tore three of them down. Why did this happen?

A. The urban setting of the Scotts Mills Dam at Lock 19 brings with it some challenges, not the least of which is the lack of space upon which set up construction staging. Construction staging accommodates the storage of construction materials, manoeuvring of machinery, and access to the construction site. Parks Canada purchased four residential properties adjacent to the dam to address this challenge and to assist with future operational and maintenance requirements.

It’s important to note that the purchase of these properties does not fully accommodate a project of this magnitude. By necessity, the project was designed to accommodate offsite storage and staging areas, and construction workers have been bussed to and from the site each day due to a lack of available parking.

Q. What will Parks Canada’s property on River Road South be used for after construction of the dam has been completed?

A. The use of new Parks Canada properties along River Road South following the completion of the project has yet to be fully determined. Parks Canada is working with the City of Peterborough to connect the trails network through Parks Canada properties, and south of Landsdowne St. It is proposed that this property become a part of that initiative. In the interim, the property will be restored as parkland, with a maintenance access driveway serving the dam.

Environment

Q. Has there been an environmental assessment done for this project?

A. A Detailed Impact Analysis was completed and distributed for public input, with comments incorporated into the work plan.

Q. Wasn’t contaminated sediment found in Little Lake? How hasd the contractor ensure that this has not gotten into downstream watercourses?

A. Contaminated sediment is present upstream of the dam. Generally, a very effective method of mitigating the risks of contaminated sediment is to leave it undisturbed, particularly in large areas like Little Lake where complete removal would be cost prohibitive. However, this option has not been available as a part of the project to replace this dam due to the location of sediment within the area of excavation. Parks Canada provided mitigation measures specific to contaminated sediment as a part of the tender documents, and the contractor was required to address these in their Environmental Management Plan (EMP) before beginning work. The EMP includes things like a complete excavation of contaminated sediment within the construction site, removal of sediment to an offsite treatment facility, and onsite treatment of water pumped out of the site. Onsite monitoring by Parks Canada environmental teams, as well as third-party consultants, has taken place during the project to ensure compliance with the EMP.

Q. Will the construction project impact fish species?

A. While effort has been made to significantly reduce the impact of construction on fish species through design changes and construction phasing, some impact on fish spawning habitat will result from the construction activities at the Scotts Mills Dam, and at other Otonabee River dams. Recognizing this, with the assistance of an environmental consultant, Parks Canada conducted assessments to determine habitat suitability for walleye in particular, and constructed a robust fish habitat enhancement to improve spawning and to mitigate negative impact caused by the work on dams along the Otonabee River.

Q. How will Parks Canada minimize impact to fish species?

A. The fisheries offsetting strategy involves the construction of new walleye habitat outside the area of construction activities, and restoration and enhancement within the project areas following construction. The aim of the strategy is to leave the overall area in the same condition or better than when construction began, and to ensure that the walleye population as a whole, and its habitat, will not be negatively impacted because of the reconstruction of Otonabee River dams.

Q. What about fish species other than walleye?

A. The Ontario Ministry of Natural Resources and Forestry (OMNRF) fish management objectives for this area support the protection of walleye habitat due to its importance to the Rice Lake walleye fishery, and the currently limited amount of habitat.

The assessments conducted review the impacts to all fish species and habitat. Centrachid (bass/sunfish) habitat is very common within this OMNRF zone and the creation of additional habitat is not a priority. To ensure no reduction of this habitat, substrate suitable to these species was included in the habitat enhancement work.

Overall, there has been an increase in available spawning substrates in the project area.

Q. Has the Ontario Federation of Anglers and Hunters (OFAH) been consulted on this work?

A. While OFAH does not have any permitting requirements as part of this work, they have participated in past restoration and monitoring efforts for the Rice Lake walleye population. Therefore, at the outset of baseline studies, OFAH was contacted for background information of the area, including previous studies and restoration work from Lock 19 to Rice Lake, which was shared with the current environmental consultant.

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