Nanaimo city council is standing by a decision, made during a closed meeting, to demolish a pair of century-old dams and drain two landmark lakes in the mid-Island community.
The decision to remove the dams from the popular swimming and fishing area at Colliery Dam Park was made by council during a closed session on Oct. 22 and was only announced on Monday.
Though the dams are stable, they no longer meet either seismic or extreme weather safety standards, said Bill Sims, city water resources manager. The geology under the dams is unknown. To rebuild the dams would cost about $20 million to $30 million, said Sims, compared to $7 million to demolish them.
He added that even it was possible to repair the dams, of which he is uncertain, the risk to the downstream community is still there.
An inundation study focusing on the consequences of what would happen should the dams fail was completed this year. It informed much of the decision concerning the removal of the dams, said assistant city manager Doug Holmes.
"If the dam stayed there, there's two ways that failure could occur," said Sims. "One of them is from a seismic activity in the right place at the right time, and that would cause the collapse of the dams and the rushing out of all the water that is retained behind them. That would go into the large flat area downstream which is a large part of Harewood."
The dam currently holds about 266,000 cubic metre of water.
The other scenario that could cause a breach is during an unusually extreme storm event that would create too much flow for the dams to handle, said Sims.
The two dams were built between 1910 and 1911.
City officials started distributing information kits and evacuation maps this week to area households that would be affected by a breach of the dam. Another significant factor in the event of a dam breach is that the responsibility of rebuilding and cleanup is on the shoulders of the city and taxpayers.
"No one's going to bail us out," said Sims.
Fisheries consultant and biologist Charles Thirkill said that the Chase River, which feeds into the Colliery Dam Park, supports thousands of chum and hundreds of Coho salmon.
He said the Vancouver Island trout hatchery stocks the reservoirs created by the Colliery dams with 3,000 trout each year, which creates a recreational fishing and swimming area used by locals.
"They weren't thinking about earthquakes when they built it," he said.
He thinks the ecological impact of draining the reservoirs will have the most effect on the osprey, eagles and heron that feed on the fish in that area.
Former councillor and long-time Colliery Dam Park user Loyd Sherry said he was disappointed the decision had already been made before Monday's council meeting and thinks more analysis should have been done before a decision was made.
"When you drain the water out, what have you got for walls? What does the bottom of the dam look like?" asked Sherry. "Do they know what it looks like? No."
One thing people will notice once the reservoir is drained, said Thurkill, will be the exposure of all the bare rocks that are now underwater. However the community could take part in the rehabilitation of that area, he said.
Rose Thoule lives near Colliery Dam Park and runs and bikes through it regularly. She said she would be sad to see the reservoir go because of its use by swimmers and children that fish in the area.
"I'm all for things going back to how nature had it, but there's people to contend with, too," she said.
Fifteen-year-old Jamie Crevier said the park is filled with childhood memories of fishing and swimming. He recently moved backto the area that would be evacuated should the dam be breached.
"Can't they just make them stronger?" he asked. Looking out at the reservoir, he added, "I feel like this is the most relaxing place in Nanaimo."
Draining of the lakes and demolition of the dams is set to begin in the summer of 2013.
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