The latest plans for the upcoming Cheekye Fan debris barrier show a concrete structure that could be 25 metres high, with a six-metre wide outlet to allow the river to pass.
Modelled after Japanese designs, it’s expected to have the ability to stop 2.4 million cubic metres of debris, which is similar to the Joffre Peaks slide, or BC Place stadium.
It’s built to withstand a major landslide event that has a roughly 1% chance of happening in the next 50 years.
These plans were revealed to District council on June 8, as part of an update on the upcoming Cheekye Fan development by Sqomish Sea to Sky Developments, a partnership between Matthews West — formerly known locally as Matthews Southwest — and the Squamish Nation.
About 1,200 dwelling units are proposed, along with commercial space in the Ross Road area in Brackendale.
The creation of the barrier is a crucial condition of a rezoning application that will allow the developers to create the new neighbourhood.
That’s because the Cheekye Fan, which is an alluvial fan, has been designated a dangerous debris-flow zone.
As a result, officials are contemplating the creation of a barrier that will be located northeast of Alice Lake, just outside the provincial park.
That area was chosen because it will protect the Cheekye Fan itself, as well as the entire park, among other things.
Climate change considerations also have to be taken into account as well, said Alex Strouth, design lead and engineer of record for the Cheekye barrier.
“Climate change will increase the frequency and size of rainstorms and those rainstorms will generate debris flows,” Strouth said.
Another key piece in the presentation was the concept of risk assessment.
One of the biggest considerations was how much money should be spent on a barrier in relation to the amount of risk it can reduce. The goal is to get risk as low as reasonably practicable, he said.
The District regulations stipulate that risk of death in existing developments should be less than 1:10,000, which is the chance the average person has of dying in a vehicle accident.
“If you’re going to live in the fan, in the existing development, your risk should be less than dying in a motor vehicle accident,” Strouth said.
But for new developments, the threshold is 1:100,000, which is similar to the risk of drowning, he noted.
The design of the proposed barrier was created with consideration to those risks, Strouth said.
There was consideration that an earthquake would likely be a triggering event for a landslide, so as a result, that is also being taken into account in the design, he said.
District staff also said a hazard map will be created, which will show the areas that possible future development and activity can occur after the barrier is complete.
Adoption of the Cheekye Fan development hinges on the successful implementation of a debris barrier.
District staff say that this will still take some time and likely won’t happen in the near future.