B.C. government officials are involved in technical examinations of an aging dam upstream from Britannia Beach part of a process that could well result in the 97-year-old dam's removal.
The elected representative for the hamlet, though, says the removal of Tunnel Dam can't come soon enough. In fact, Maurice Freitag, Squamish-Lillooet Regional District (SLRD) director for Electoral Area D, on Friday (May 24) said the dam is an accident waiting to happen.
Tunnel Dam was built in 1916, four kilometres upstream from Howe Sound, to supply power and water for the Britannia Mine and community. In recent years sediment from the upstream Jane Basin has filled in what was once the reservoir, to the point where there are plants growing in the sediment directly behind the dam's crest.
Freitag said that because of the area's geography, even a major failure of the dam would have limited impact on the residential and commercial areas of Britannia Beach. But structures directly in the path of the torrent such as the new Highway 99 bridge over the creek could be washed out, similar to what happened on Rutherford Creek south of Pemberton during the 2003 flood, he said.
The last time there was a slide there, it would have taken the bridge out and the rail track out and it'll stop the flow of traffic north and south for an extended period of time, Freitag said.
What's going to happen to Squamish if the highway goes out for three weeks, or with one-lane traffic? What's going to happen if there's a washout like what happened at the Rutherford and people are put at risk?
I'm literally just waiting for the day it does. It's only going to take a big snowpack coming down or just the right combination of conditions and this thing rips.
Frank Baumann, a geological engineer who conducted assessments of the area in the 1990s, said a dam that posed a similar risk when the community of Furry Creek was built was purposely breached to reduce the risks. He said he'd like to see officials take similar action with the Tunnel Dam.
The issue is that if a section of the dam collapsed, water would quickly flush all that gravel through the break and allow it to rapidly flow downhill, Baumann wrote in an email to The Chief. This could really happen at any time of higher runoff, but would most likely occur during a period of really heavy runoff or, of course, if there was an earthquake.
In the case of the Furry Creek structure, the original development company, Tanac, was forced to breach and stabilize the dam in a controlled manner to make sure it didn't cause a problem. I would think that Britannia needs to do the same.
Online files show that as recently as the mid-2000s, the Tunnel Dam was owned by a firm called Copper Beach Estates, a real estate company left over from the 1974 closure of the Britannia Mine. The company later went into receivership and Tunnel Dam is now owned by B.C.'s Ministry of Forests, Land and Natural Resource Operations, Glen Davidson, director of the ministry' water management branch, said on Tuesday (May 28).
In 1989, officials breached two dams upstream from Tunnel Dam, resulting in sediment filling behind the remaining Tunnel Dam, according to a 2002 consultant's report titled Britannia Creek Flood Risk Assessment. In August 1991, a debris flood deposited large quantities of gravel in the town, the report stated.
Davidson said Tunnel Dam is one of 1,400 dams that are regularly monitored through his office. He said it only makes sense to take steps to mitigate the risks a failure might pose to life and property.
It's completely filled in, so it's not serving any useful purpose, he said.
The difficult, he said, is deciding on the right course of action.
You can't just remove the dam; first you've got to deal with the sediment that is there, Davidson said. So the questions we're trying to determine are how you'd go about taking it down and the cost of that process if that's the decision that's made.
We're got some technical examinations to do first, then evaluations of what to do with it, and then after that would be cost estimates I would suggest by next summer [2014] we would at least be in a position to have some options and to begin examining the cost of those options.
Freitag said that if the SLRD owned the dam, a solution would already be forthcoming.
What they've been doing is passing the project around from engineer to engineer and they haven't settled on any sort of plan to fix the dam and reduce the risk.
The Province owns it. They've received royalties from the mining companies for years and years, so there's money set aside. Why wasn't the work completed?
