Proposed fish ladder at Site C dam called ‘bizarre,’ but is quite common

Of all the jobs created by the $8.8-billion Site C dam that's now under way on the Peace River, perhaps the most unusual is fish chauffeur, or trout bus driver if you prefer that title.

The job posting hasn't been made yet, but it is called for under the fish-management plans BC Hydro has filed as part of the environmental-assessment process.

Under the strategy, BC Hydro would build a fish ladder at the base of the dam that would lead to an "anesthetic pool," where bull trout, Arctic grayling and other species would be trapped, drugged and loaded into tanker trucks. They would then be bused around the dam, to be released in the upstream tributaries where they spawn.

The cost of building what is known as a trap-and-haul operation is about $25.5-million (fish ladders don't come cheap) and there will be annual operating costs of about $1.5-million.

The cost of keeping the bull trout and other fish running to their spawning beds over the projected 70-year lifespan of the dam is going to be more than $130-million.

BC Hydro's fish-management plan, which the online magazine DeSmog Canada has called "bizarre," was filed in 2012. But until writer Sarah Cox dug out the details recently, the plan had been lost in appendixes among thousands of pages of documents filed by BC Hydro.

In an e-mail Friday, BC Hydro spokesman Craig Fitzsimmons said the plan outlined in the environmental-impact statement is "preliminary … and will be updated and submitted prior to the river-diversion phase of the project – the first activity that will affect upstream fish passage."

The plan may seem strange – and costly – but trap-and-haul systems are well established in North America and have been shown to work. Perhaps the most dramatic example is on the Columbia River, where dams block the migration routes of salmon and steelhead. While the dams on the lower section of the river were built (starting in 1938) with fish ladders, fisheries managers soon realized that spawning salmon moving upstream, and juvenile salmon migrating downstream, needed extra help.

Three of four dams on the Snake River, a major tributary of the Columbia, and one dam on the Columbia itself have fish-transport facilities.

Adult salmon migrating upstream on the Columbia are trapped and trucked around dams. Juvenile salmon are trapped and barged across reservoirs on their downstream journeys. Between 15 million and 20 million salmon and steelhead are typically transported each year on the Columbia.

The Columbia dams also have bypass systems that try to divert fish away from dams and into safe passages, so they don't get swept into turbines as they migrate downstream.

BC Hydro has proposed a number of possible downstream solutions, including grates that will divert larger fish away from the turbines, but the plan acknowledges it will be impossible to screen out all the smaller fish. Many will go into the turbines and up to 30 per cent of them will be killed.

One technical memo filed by BC Hydro describes the many ways a spinning turbine can fatally damage a fish. In a "strike" they are driven against a solid structure at high velocity. In a "shear" death, they are battered and stripped of scales when hit by different velocities of water "on either side of its body at the same time."

A "grinding" death occurs when a fish is caught between moving and stationary mechanical parts. There are also deaths by pressure changes that "can result in bursting of the swim bladder" and something called "cavitation" which happens when vapour bubbles collapse, causing localized shock waves.

The Peace River is rich in fish life, particularly in the region near Fort St. John where the Site C dam is to be built.

Bull trout, rainbow trout, kokanee salmon, whitefish and many other species migrate through the area each spring and fall. They have been doing that since the glaciers melted, and when they suddenly find their way blocked with a massive concrete wall, they simply won't know what to do.

One of the Site C fisheries papers notes that placement of the channel opening for the fish ladder will be crucial. If it is not obvious and inviting to the bull trout and other fish, they will simply swim past it. If that happens, the $123-million fish-transportation program will fail.

If everything works as planned, the fish runs will probably survive – as long as they can hitch a ride.