Removal of old dams brings fish back to Britannia watershed

Bruce O’Neill has respect for the men who built a series of concrete dams in the Britannia Creek watershed to create the hydroelectricity that powered the largest copper mine in the British Empire.

That was a century ago. Today, the dams must go because they represent a safety concern to the public downstream in the event of an earthquake. Some are also being undercut by water and are vulnerable to failing in a major flood.

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“When they were built, in the mid-1910s, no one had any idea of the earthquake potential here,” reflects O’Neill, a dam project director with the Ministry of Forests, Lands and Natural Resource Operations.

He watches an excavator with a rock hammer chip away atop 24-metre-high Lower Dam, pulverizing the concrete into chunks consistent in size with those found naturally in the creek. The chunks are considered essentially inert and no danger to fish and are being left to become part of the environment.

“It’s stood up amazingly well,” O’Neill observes of the structure. “What we tear down in 10 minutes probably took 40 guys the better part of a week to build.”

The province is spending about $1.5 million in an unprecedented operation to decommission, in all or part, six dams between West Vancouver and Squamish in the Britannia watershed — three last year (Park Lane, Utopia Lake, and Tunnel), two this year (Lower and Mountain Lake) and one in 2017 (Mineral Creek). A seventh small dam, Marmot Creek, is “small and low consequence,” and is not being dismantled, he said.

While public safety is driving the project, removal of the dams also benefits fish and other aquatic life. Dolly Varden have already started migrating downstream, complementing the 300 pink and three dozen chinook salmon found in the lower river last year. Installation of a water-treatment plant in 2005 resolved a long-standing problem with acidic rock drainage and the leaching of toxic metals associated with the old mine. The plant allowed the return of salmon to spawn here again. This year, a juvenile rainbow trout was also discovered in the lower river.

It’s all heady stuff for the Outdoor Recreation Council of B.C., which declared Britannia Creek the most endangered river in B.C. in 2001.

“There are few, if any, examples of so many dams successfully decommissioned in a single watershed over a fairly short period of time,” remarks Mark Angelo, the council’s river chair. “It makes the work here unique.”

Geoff Smart is a biologist with EBB Environmental Consulting who is monitoring the demolition of Lower Dam, to ensure that pH levels and turbidity meet B.C. water quality guidelines. So far so good, but it’s early days. The demolition project could take close to two months. “We’re about 10 minutes into it now,” he says.

Further up the watershed, the province last year opened up a four-by-nine-metre notch in Tunnel Dam. An estimated 30,000 cubic metres of gravels and sediments had accumulated behind the structure and have been washed downstream to create more natural stream beds, including opportunities for fish to spawn.

The water now flows freely through the notch, forming a minor waterfall that fish can pass through and recolonize areas upstream. Water levels rise and fall naturally with the rains and snowmelt. The site must be maintained, however, so that fallen trees and other debris don’t plug the notch.

The Britannia Mine opened in 1904 and closed in 1974 and is now a national historic site offering public tours.

South of the border, in Washington state, the 33-metre-high Elwha Dam was torn down starting in 2011 in the Olympic Mountains, the largest dam removal in U.S. history.

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