An engineer has given the Town of Oliver some expert advice on the Gallagher Lake siphon dilemma.
Steve Underwood from TRUE Consulting is working with council to address the concern regarding the potential of another rockfall damaging the irrigation canal.
The Town is currently waiting for funding from the federal government to reroute the canal around the lake along Highway 97. The estimated cost is $10.5 million. The provincial government has already committed $5 million.
But in the meantime, there is worry that another rockslide could damage the siphon again like it did in 2016.
Underwood said adding additional cover to the canal might protect the structure from future damage, but it would be very expensive.
He said the 2016 rockfall was so large it made a crater in the ground where it landed, (the rock was as big as a dump truck).
Underwood said the repair that was completed in 2016 was constructed very well and worked beyond anyone’s expectations. He pointed out the repair, in its third year of service, has shown no sign of deterioration. However, the repair limits the canal to 70 per cent of its capacity.
“In its current state the repair should last 20 years (16 more years) based on the materials used.”
But Underwood said the repair would likely not survive the next major rockfall.
When the next rockslide crushes the canal, temporary pumps and pipe will need to be deployed to pump the canal around the failure, the engineer said.
Underwood said the cost to pump 20 per cent of the canal capacity would be approximately $300,000 per month. “If the rockfall were to occur in the summer, it would cost $900,000 per month to pump 60 per cent of canal capacity.
Underwood said 100 per cent funding would likely come from Emergency Management BC. But it might take another rockfall to trigger the funding, he pointed out.
Town council will discuss the engineer’s report on Monday.