Options for Esox Lake dam

With the aid of maps and charts, the MNR illustrated last week the five alternatives as to what can be done with the Esox Lake dam, which is located north of Devils Cascade and affects water levels along the entire Manitou watershed stretching 60 miles northeast of it (including Esox, the Manitou Stretch, Lower Manitou, and Upper Manitou).
•Do nothing
No work would be done to repair the dam, and it would be left to naturally break down.
While this would have no cost as such, it ultimately would be a liability issue as water levels eventually would revert to those as if the dam were decommissioned (just not in a controlled fashion) and adversely affect property owners.
The dam would be repaired to address current safety and liability concerns, and would extend the life of the existing structure by an estimated 20 years.
This would involve major concrete repair, which requires de-watering of the working dam site through the installation of a temporary coffer dam that would divert the water flow during the time the work is being done.
This would cost less than reconstruction, but maintenance costs would increase in the long-term. Manual operation of the dam would still be required.
There would be no significant impacts to current lakefront property, recreational, navigational, and commercial users on the lake as the lake level would remain as it is now.
•Reconstruction (control structure and weir)
The existing dam would be replaced with a new structure that would have three stop log bays and a weir. This would involve a new dam location downstream from the existing one, and require de-watering of the working dam site during constriction.
The dam would have a higher discharge capability than the existing dam.
This option would require less operational and maintenance requirements for roughly 40 years. But the proposed work would require very high initial costs, and again in 40 years.
This alternative still would require manual operation of the dam, but the requirement would less than that of the rehabilitation option.
There would be no significant impacts to current lakefront property, recreational, navigational, and commercial users on the lake, but a fish habitat inspection has determined there would be short-term habitat loss, and that compensation would be required.
•Reconstruction (overflow weir)
This alternative would see construction of a new dam downstream from the existing one, with a 17 m long overflow weir.
The height of the weir would be lower than typical summer water levels under existing dam operations, causing lake levels to lower across the entire system by 0.4 m.
This option would eliminate future dam operation and minimize maintenance requirements. It would have a high cost initially, but still cost less than the rehabilitation and other reconstruction options.
The lower levels would have some impact on navigation, lakefront access, and fish and wildlife habitat, but not to the extent of the decommissioning alternative.
Navigation would be reduced relative to existing conditions. Under normal conditions, channels would provide roughly 0.5 m or greater depth. The weir would result in greater variation of depth relative to the normal level in comparison to the operated dam.
Currently water levels, on average, fluctuate less than a foot throughout the open water season; this would increase with a weir.
There would be lakefront recession of roughly six metres in certain areas, which would require tourism operators and property owners to relocate and/or lengthen docks, and possibly relocate existing infrastructure.
But a weir would result in more natural flow patterns throughout the system and benefit fish and wildlife. The drop of 0.4 m would not result in any acute short- or long-term concerns for the natural environment.
After a complete assessment of environmental and social impacts, a strategy would be developed for complete removal of the existing structure.
This alternative would allow for restoration of natural water levels throughout the chain of lakes. Decommissioning could occur in stages over a period of 10-15 years, resulting in gradual reduction in water levels.
Water levels would drop by an estimated 1.2 m on the Manitou Stretch, as well as the Upper and Lower Manitou, and 2.9 m on Gussie Lake and Esox Lake.
There also would be, on average, a lakefront recession of 18 m, requiring tourism operators and other property owners to relocate and/or lengthen docks, and where applicable, relocate or retrofit existing infrastructure.
Channels, namely Esox Narrows (east and west), Four Miles Narrows, and Birch Narrows, would become non-navigable after the dam’s removal (at least for the dry time of the year), and navigational hazards in other relatively shallow areas within the lakes would be expected.
And the lake system would be isolated into three sections for part of the year—Esox Lake and Gussie Lake; the Manitou Stretch and Lower Manitou Lake; and Upper Manitou Lake.
A review of alternative lake access points would have to be done.
Removal of the dam would not have any impact on fish migration, and no specially-protected species of fish or wildlife would be affected.
In the long-term, this option would benefit fish and wildlife by restoring natural flows. The animals’ communities that exist here have evolved over 10,000 years in that system, and only have in the last 50 years accommodated higher levels.
Therefore, it is assumed, said the MNR, that species would accommodate to the change in lake levels and benefit from the natural flow pattern that would result.
This option would cost significantly less money than the others, and would eliminate future dam operation and maintenance costs and requirements.
Hill said yesterday that exact costs of the options will be included in the packages she will send out, but added that from the MNR’s viewpoint in this project, “cost is not a deciding factor.”