About 50 residents passionate about a major part of the community came to the community centre here on Sept. 2 to see proposals for the failing Drimmie Dam.
The dam is located just upstream of the Elora Mill Inn, and is used by that business as a source of hydro.
But the concrete structure is failing, as photos provided by Sanchez Engineering Inc., of Coburg, showed. There are large cracks in it and places where the concrete has disappeared.
The Grand River Conservation Authority attempted earlier this year to shore up the structure, fearing for the safety of downstream users if it suddenly gives way, but that plan was overturned by the Ministry of Natural Resources.
Residents were presented by Sanchez with five options for the structure. They include:
– remove the dam and restore the river;
– build an entirely new dam upstream of the Metcalfe bridge;
– reconstruct the current dam, with the provision of lowering the pond built up behind it;
– rebuild the dam at the same place with the same configuration; and
– do nothing at all.
The first option has several advantages:
– increase the discharges capacity of the reach between Metcalfe Street bridge and the Elora Falls;
– estimated flood damage in the current situation are $1.9-million. With the dam gone, the flood damage would be reduced to about $300,000;
– improvements to the diversity of the river channel on the bases it would be restored to a natural channel section with pools and riffles and appropriate riparian vegetation and stream cover.
The disadvantages of that proposal include:
– loss of hydro generation capacity;
– the lower head pond would lower the tailwater levels at the Bissell dam upstream and might require scour prevention measures;
– potential sedimentation downstream for a while;
– loss of the use of the headpond by riparian owners.
Rebuilding the dam at the same location has advantages:
– stabilization of the dam for safety;
– improvement of safety for river users, especially in the Elora Gorge; and
– keeps the current head pond elevation for power, recreation, and other uses.
Disadvantages are:
– using the current dam base will reduce its durability;
– the cost of rehabilitation is not significantly lower than replacing and rebuilding a new dam; and
– no reduction in the flood levels in the vicinity and upstream.
A new dam upstream of the Metcalfe Street bridge would have these positive effects:
– increase the discharge capacity of the reach between the Bissell dam and Elora Falls; and
– improve diversity of the river channel, because it would be restored to a natural section.
The disadvantages:
– need to relocate the inlet of the hydro plant of the Elora Mill Inn to the new dam;
– potential sedimentation downstream until the pond because stable; and
– loss of use of part of the head pond by riparian owners.
To rebuild the dam but lower the head pond levels has these advantages:
– stabilize the dam to meet safety regulations;
– possibility of lowered flood risks by opening the control structure to accommodate the river flows;
– reduction in flood damages between the dam and Metcalfe Street by $1.6-million; and
– maintain the current head pond elevation for hydro, recreation, and other uses.
The disadvantages:
– using the current dam reduces its durability;
– the cost is not significantly less than a new structure being built with provision for a lower pond elevation; and
– the head pond level could change and affect the power generation station and other uses.
Doing nothing would have the following consequences, given that the dam will fail:
– loss of hydro generation capacity;
– potential of injury or death to users downstream;
-potential fisheries damage due to the sudden uncontrolled release of sediment form the head pond; and
– the cost of restoring or replacing the hydro generation capacity to the Elora Mill.
Merchants want the dam
For Elora Mill Inn General manager Matthew Phillips, the dam simply has to be there, one way or another.
He cited the head pond and merchants provides numerous brochures touting Elora that featured the head pond and the Elora Mill Inn.
Phillips also noted that riparian law states a mill cannot be denied sources of power. He said that law was passed years ago when Canada was at war because mills supplied food and woolens for clothing.
Marty Van Vliet, an executive member of the board of directors for the Elora BIA, sent written comments to the chairman and board of directors of the Grand River Conservation Authority.
He wrote, “The view across the mill pond is part of the package that we sell to visitors. It quintessentially is Elora. As you look across the pond, the buildings of Mill Street and the Mill are reflected in the water. Swans swim around, people walk down to the boardwalk, to gaze into the water. It is serene and peaceful or, as our ad campaign said, “It’s a world away.”
Van Vliet also noted that merchants are still hearing comments of disbelief that the Victoria Street walking bridge over the river just upstream of the dam was removed, and that occurred in 2006.
‘If we lose the dam as well, will people still find us unique enough to visit? Hundreds of jobs and a pile of tax dollars hinge on that decision.
In an interview, engineer Leonardo Sanchez said that the comments were almost evenly divided between taking the dam out altogether and keeping it in in some way.
He agreed that the proposal to build a dam upstream of Metcalfe Street appears to find the least favour.
“People thought it wouldn’t be practical,” he said. “We didn’t think that it would go that way in any case.”
Still, he said it was an option that needed to be presented.
He noted that there were complaints that photos provided for the open house had been unrealistic in showing certain phases of the river, and he said those would be replaced. He added there will be more public consultation on the issue.
The complaints stemmed from photos purporting to show the river once the dam is removed. Many complained that the view, with a full head pond, was unrealistic.
Sanchez said the community liaison committee will meet again, likely in mid-October, and he expects more public consultation at the end of that month, or the start of November.
He added that he expects his work of laying out options for consideration will be completed by the end of the year.
