How long before the dam fails?

    Predicting when a structure that is over 100 years old will fail is very difficult and depends on several variables. Indicators such as the structural condition of the dam are used to indicate the potential for failure. Recent investigations (2018) have determined that portions of the dam are in very poor condition and that the risk of failure is consequently “high”. As such, the City of Cambridge is continuing to conduct regular inspections of the structure until the dam is replaced.

    Who owns the dam?

    While ownership of the existing dam is uncertain, it is known that the City of Cambridge does not own the existing dam. However, the City has worked as the proponent for this project and will own the new dam.

    Why isn’t the existing dam just being repaired?

    During the Class Environmental Assessment, the “Repair the Dam” alternative was screened out. The Repair the Dam alternative did not have any advantages over the rebuild alternative, and a repaired dam would not retain the heritage integrity in the materials and details because of the amount of new construction and repair work needed. Furthermore, it would not have as long a service life as a new dam.

    What will be the impact of the project to Sulphur Creek? Will water in the creek and pond be maintained?

    There will be no impact to Sulphur Creek after construction, and the water in the creek and the pond will be maintained. During construction, flows from the Speed River work area will be diverted into Sulphur Creek to allow construction of the new dam and related work to proceed in dry conditions. During that time, the creek will flow entirely as a normal creek, passing all the river flows. Once construction is completed, flows will be returned to the Speed River and Sulphur Creek will be restored.

    What will the sediment management plan entail?

    Details of the sediment management plan are being developed as the detailed design proceeds. The plan will be dependent on the preferred alternative and the volume and quality of the sediment that will be impacted. Approval of the sediment management plan will involve consultation with the regulatory agencies, particularly the Ministry of the Environment, Conservation and Parks (MECP).

    Who will be covering the cost of the proposed new dam?

    The City of Cambridge will be responsible for the cost of designing and constructing the project. The design costs are in the current City budget. The construction costs will be debt financed. The City will also investigate other funding opportunities that may be available.

    When will construction start?

    The tentative schedule is for construction to start in the summer of 2022. Work is planned to be completed in 2022 and 2023. This will be dependent on budget approval and obtaining all necessary permits.

    When the existing dam is removed and the new dam is constructed, will the CP railway trestle bridge be affected?

    The trestle bridge is located just beyond where the river flow is affected by the existing dam and the new dam will be further upstream and will therefore have less impact on the CP railway trestle bridge. CP has indicated that it is waiting for the new dam to be constructed to decide on the preferred approach to repair or replace the existing trestle bridge.

    When the new dam is constructed will the headpond be the same size as the existing headpond? When the gates are open what will happen to the headpond and river?

    The headpond with the new dam will be at the same water level, but it will be smaller than now because the new dam will be about 40 m upstream of the existing. The section of the headpond from the new dam to the current dam will become a free- flowing river, similar to the river downstream of the existing dam. When the gates are open, the entire river will be free-flowing and there will be no headpond.

    What will happen to the shoreline downstream of the new dam since the river will be narrower?

    The river will be restored and the new banks will be protected. The existing shorelines will become part of the river overbanks.

    What will happen to the materials from the existing dam when it is removed?

    It is proposed to use some of the cut stone from the control structure in a heritage interpretative feature that will be located in the park. The form and design of the feature will be developed as part of the design process. The concrete and rocks that form the lower part of the dam will be removed and disposed of as demolition material.

    Does this project have any negative impacts on the natural environment?

    Replacement of the existing dam with a new structure will have positive effects by permitting year-round passage for the resident fish community, re-establishing a natural sediment transport regime to the Speed River and returning a portion of the river channel to a more natural state upstream and downstream. Overall, there will be a net improvement to the natural environment.

    Will fishing in the headpond be affected?

    The headpond will remain during the late spring to early fall period. As fish passage is included in the design of the new dam structure, there is the potential for more fish species to make their way to the headpond from the downstream reaches. Fishing upstream of the new dam when the gates are open will be like fishing in the free-flowing river.

    What is the heritage value of Riverside Dam?

    The heritage value of the dam has been recognized by its listing on the Municipal Register of Properties of Heritage Value or Interest. The heritage features that were identified in the Cultural Heritage Evaluation Report done as part of the EA process are the north and south control structures, particularly the stone arches and buttresses.

    Are there other features of heritage value?

    Other heritage features include:

    • The scenic parkland setting, mature specimen trees and open lawns overlooking the headpond and Speed River above and below the dam.
    • The association of Riverside Park with Frederick G. Todd, landscape architect named as a National Historic Person (one of only 5 in Canada) and a leading public figure of the community in the early twentieth century.
    • The historic Indigenous use of the area, and the industrial activities centred on milling that were the foundation for the early prosperity of Preston.
    • The Memorial Arch and Gateway to Riverside Park designated under Part IV of the Ontario Heritage Act and part of the cenotaph movement in Canada after WWI.
    • The connecting links between river, roads and railway as a historic means of reaching markets outside the area.

    How will the heritage value of the Riverside Dam be recognized?

    Commemoration of the heritage value will be by a new landscape feature that integrates the salvaged stone from the control structures with interpretative panels sharing the many messages about the history of the dam and its setting.

    Will the project have an impact on railway operations? Will the railway bridge be reconstructed as part of the project?

    The City and CP Rail are working together to ensure that rail operations continue safely during the project. The project does not include any changes to the railway track or bridge.

    Why is the new dam located upstream of the existing dam?

    The new dam will be located upstream of the existing dam to provide better separation from the railway bridge. It will also allow a portage around the dam within the park. As well, by providing separation from the railway, a better vista will be created from the King Street bridge and from within the park.

    Will all of the sediment in the headpond be removed?

    It is proposed to remove only the sediment between the existing and new dams, and to relocate the sediment within the headpond to form a channel.

    How is fish passage being addressed in this design?

    Fish passage during the summer months when the gates are closed will be provided by a new "rocky ramp" low-flow channel. Flows will be tailored to ensure that small and medium sized forage fish (the main types of fish in this reach) are able to pass. The rocky ramp will be constructed of large cobble and boulders, and will be built extending from the downstream pool to a fishway access notch in the south end of the spillway structure. In the fall/winter/spring period, fish will be able to pass through the open gates to access the restored, upstream channel.

    How will canoeists get around the new dam?

    The design and construction will include a portage and signage to provide canoeists/kayakers with a safe route to get around the dam.