Here is an aerial photograph of the Bala north dam and north falls (click on it for a larger view). North is to the left, and the water from Lake Muskoka flows west through the Bala north channel, first under the Canadian Pacific Railway bridge and then under the Muskoka Road 169 bridge, the over the stop-logs of the Bala north dam, and down the Bala north falls to the Moon River.
To the right of the Bala north dam is the 71′-wide parcel of Crown land which the proponent proposes to excavate to build their proposed generating station. To the right of that is “Portage Landing”, owned by the Township of Muskoka Lakes and designated under Part IV of the Ontario Heritage Act as a cultural heritage site.
The proposed station’s intake would be 40′-wide, between the Bala north dam and almost to the Muskoka Road 169 bridge. The water would exit the proposed station’s tailrace south of the Bala north dam.
The three-dimensional rendering below was provided by the proponent and is from a similar vantage point (click on it for a larger view). As above, north is to the left, and the Muskoka Road 169 bridge is just upstream of the Bala north dam. The rendering has been marked-up to highlight that the proponent would need to excavate:
- A 30′-deep intake, just upstream of the Bala north dam. This excavation would be closer than directly adjacent to the dam – the proponent would even cut off the upsteam nosing from the dam’s south pier, so that the intake to their proposed generating station could be as wide as possible.
- 45′ down, directly south of the Bala north dam, for the proposed generating station.
The Bala north dam, which is over 100 years old, would then be perched at the edge of a 30′- to 45′-high cliff. Major repairs would be required if:
- This blasting and excavation affects the bonding of the dam to the bedrock below it (the Bala north dam is a concrete gravity dam, and depends on the weight of the concrete piers and their bonding to the bedrock below to withstand the horizontal force of the water).
- The dewatering of the excavation lowered the water table such that the 150′-long Bala north dam tilted and therefore cracks formed in it.
- Removing the concrete wing wall (which prevents water from infiltrating the shore where the old generating station’s intake used to be) affects the stability of the Bala north dam.
- Removing the upstream nosing from the Bala north dam’s south pier (proponent plans to do this to increase the width of the proposed intake) affects the Bala north dam (the nosing was added for a reason).
- The deflector wall (required to more evenly direct the water into the proposed intake) causes horizontal forces for which the Bala north dam (and also the piers supporting the Muskoka Road 169 bridge) were not designed.
Have these risks been analysed. Who has checked the information from the proponent (this is an unusually complex situation), the MNR used to have significant in-house technical resources, but now relies more on outside consultants. What assurance does the MNR have that the public would be indemnified from any damages caused by the proponent, for example through poor planning, rushing, or unexpected situations. If there was a “high flow event” and the upstream cofferdam had to be quickly removed, how long would it take to be sure that the Bala north dam could handle the flow.
This would not be not routine construction, this is work that could both encounter significant additional construction difficulties and damage existing infrastructure. The impacts on the MNR, the public, and the proponent and their investors could therefore be substantial.
These are big risks and the MNR’s process is too secret to know whether the public’s interest is being adequately protected.