The recommended action for the failing Drimmie Dam in the downtown here is to rebuild it – but about 18-inches lower than the current structure.
Dozens of citizens viewed the options and the thinking behind the report by Sanchez Engineering on Dec. 9 at Veterans Hall.
The class environmental assessment was done by Sanchez Engineering Inc. for the Grand River Conservation Authority in 2008, and this was the second public meeting to present the results of a study on what to do with the dam. The option that was chosen was labled B1, and its estimated cost is $1.25-million.
That option was not the one likely to reduce the most flood damage, but it was the cheapest of four options that made the final cut out of a list of nine choices.
The recommendation to rebuild pleased Elora merchant Marty Van Vliet, who is a member of the Business Improvement Area executive.
“It’s a reasonable alternative,” Van Vliet said in an interview after he had worked his way through a dozen display boards that showed what was studied and how the conclusion was reached.
“It maintains the mill pond, on which 100 businesses are dependent,” he said.
Van Vliet added that lowering the dam about half a metre also means “the lower level reduced the flood risk to business along the river.
But Fergus resident Keith Fairfield was unhappy with what he saw at the public meeting.
“We’re desperately short of money in this municipality,” he said. “Centre Wellington should not be spending” any money on a new dam.”
He said a new dam is something that will benefit only a very few people, “and other people do not have that much to gain from it.”
GRCA spokesman Cameron Lynnwood said in an interview that the dam belongs to the GRCA, and it will be responsible for the costs to rebuild it.
He said the conservation authority is working on federal and provincial infrastructure grants for the project, just as area municipalities across Ontario have been doing for roads and bridges over the past year.
We’re still getting notified there are other grants available,” he said.
The plan that was chosen was not ranked the best in terms of flood control or other costs, but Lynnwood said the site selected is a good choice in terms of value for the dollar.
A consideration to reconstruct the dam exactly where it is with gates to increase flow capacity during floods was considered, but it came in at a cost of $2.04-million, as opposed to the $1.25-million for the option that was recommended.
The study eliminated five options entirely, for various reasons:
– do nothing;
– rehabilitate the existing dam by doing only the work necessary to bring it into good condition;
– rehabilitate it with gates;
– reconstruct it upstream; and
– remove the dam and rehabilitate the reach.
The options, other than the one that was eventually chosen that were considered (with cost) included:
– rebuild a new dam at the same site the same way, $1.3-million;
– rebuild a dam with gates $2.04-million; and
– rebuild the dam, but as in the latter choice, but make it 18-inches lower, $1.93-million.
Lynnwood said the GRCA would ultimately make a decision on what to do after the evaluation process is completed.
He noted that opinions were “mixed” about the recommendations. “Some are happy about flood control, culture, and heritage issues, and some say why rebuild at all.”
If the dam is built as recommended, Sanchez recommended several steps in rebuilding. That includes starting downstream with a cofferdam and road with culverts. Next is to construct a cofferdam upstream, then remove the exist-ing south section of the dam, then build the south section of the dam.
Then, the same work would be done for the north side of the dam.
When all that work is done, the river would be restored with the removal of the cofferdams and road.
A cofferdam is a temporary structure tight enough so that water can be pumped out of the structure and kept out while construction on the foundations is in progress. Some common cofferdam types are earthen, steel sheeting, wooden sheathing, and crib.
The dam was constructed in the 19th century to control flow for operation of the adjoining mill, which is now the Elora Mill Inn.
The dam was repaired and a micro-hydro generation station was constructed at the site in 1984 to provide power to the Elora Mill Inn.
As part of the environmental assessment, a public liaison committee was created with representatives of groups with an interest in the future of the dam including business, tourism, heritage, kayakers, anglers and the Township of Centre Wellington.
Anyone wishing to see the report can find it on the GRCA website.
