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A rock slide on the Fraser River near Big Bar, B.C., has created a five-metre waterfall that is blocking the passage of salmon./The Canadian Press

The co-ordinated effort to save hundreds of thousands of salmon hampered by a rock slide in British Columbia’s Fraser River is about to get even more technical.

Leri Davies, the information officer with the Big Bar landslide integrated incident command, says crews have almost finished clearing debris from a cliff face that sheared off last month, dumping tonnes of rock into the river.

The slide has created a five-metre waterfall at a narrow section of the fast-flowing river potentially stopping salmon, including some species of concern, from reaching spawning grounds.

Ms. Davies says now the loose rock overhead has mostly been removed, crews are safe to focus on how to help returning salmon past the blockage.

She says water-filled, gravel holding ponds are being dug and salmon from below the slide will be placed in the ponds and then scooped up in helicopter buckets, carried above the slide and released to continue their upstream journey.

Work to drop massive boulders into the water directly under the cliff is also beginning, with the hope the boulders will form a series of pools that fish can use as resting places while hopscotching their way up the side of the waterfall.

“As each rock is placed under the cliff, it is being evaluated for effectiveness,” Ms. Davies says.

More rocks could be added to increase the size of the resting pools, but Ms. Davies says every option is complicated by the swift-flowing water, which can sweep away even the heaviest objects.

The bucketing and boulder placement are just two of the proposals developed by the biologists, hydrologists, geotechnicians and others who have been working exhaustively to save the fish, Ms. Davies says.

“The size of the response indicates to me how seriously both levels of government are taking this,” she says, adding members of 16 First Nations representing 54 bands living above the slide have also been involved in the process.

A statement on the B.C. government website says affected salmon runs include spring and summer chinook, early Stuart sockeye and early summer and summer run sockeye, all listed as species that are a significant conservation concern.

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