A huge slide of silt in March has muddied the Cowichan River. (Submitted photo)

A huge slide of silt in March has muddied the Cowichan River. (Submitted photo)

Study of landslide into Cowichan River expected soon

Up to 800 dump truck loads of glacial silt slid into river

Geotechnical experts have been hired by the Cowichan Watershed Board and other groups concerned about the health of the Cowichan River to determine the best path forward after a major landslide in the waterway in late March.

Spokesman Parker Jefferson said unusually heavy rain and melting snow during the winter months have caused a mudslide of glacial silt at Stoltz Bluffs, midway between Lake Cowichan and Duncan, that has dumped approximately 800 tandem dump trucks of silt into the river.

The slide has caused the water downstream from the slide to take on a white-grey colour, and the amount of silt that has found its way into the river has raised concerns about the health of salmon eggs laid last year.

Jefferson said a remediation project at the site was already completed in 2006 to deal with the issue, and it has been successful in keeping severe problems in check until now.

He said a study at the time had determined that the survival rates of chum salmon eggs downstream before the remediation project, which involved the construction of a berm designed to hold the sloughing clay in a settling pond, was less than five per cent.

“(The remediation project) worked beautifully and the survival rates of those eggs increased to 85 per cent,” Jefferson said.

“I think this year’s slide probably won’t impact the salmon eggs that were laid downstream last year much because, as the slide happened in late March, the young salmon had probably begun to emerge from their eggs before that.”

Jefferson said bringing in an excavator this spring to clear some of the material and possibly divert some of the water around the glacial clay bank that’s the cause of the problem is being considered.

But he said that would likely be just a temporary measure until more permanent solutions are found.

“The excavator would also have to be brought in through a campground, which is the only available route, and that’s probably a non-starter with camping season about to begin,” Jefferson said.

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