Officials in Williams Lake, B.C., are growing concerned that further erosion due to flooding in the Cariboo region could send its raw sewage towards the Fraser River.
Additional homes were ordered to evacuate Saturday and Sunday as a flood warning remains in effect for the Chilako River southwest of Prince George, along with tributary rivers surrounding Williams Lake, Cache Creek and other nearby communities in the central Interior.
The Cariboo Regional District issued multiple warnings for single properties in rural areas. A full list of evacuation orders can be found on the district’s website.
The River Forecast Centre said Sunday that the water level in the Chilako has slowly receded by 12 centimetres, after rising by more 35 centimetres in a single day late last week. Other rivers in the flood warning zone are holding steady and are expected to recede.
However, the centre warns levels could rise again if there is “significant precipitation or sudden increase in temperature.”
It’s the expectation for warming weather that has officials worried.
“From what everyone tells me, the worst of it hasn’t come yet,” Williams Lake Mayor Walt Cobb said Sunday.
The city’s sewage pipeline is connected to a series of treatment pools in the Fraser River valley, which treats the wastewater before sending it into the river. The road to the treatment ponds has been fully washed out.
Cobb and the city’s municipal service director Gary Muraca both say if a landslide comes down in the valley, that lagoon system would back up and overflow into the river. While that water would not be as clean as fully treated water, it would still be relatively safe, the mayor said.
If the landslide were to come down above that area, it could expose the sewer line, and “then there is an issue,” Cobb said.
Muraca estimated the treatment pools have a combined capacity of 160 million litres. He added debris has been falling “regularly” upstream of the lagoon system ever since the flooding began.
Cobb says the city’s local state of emergency is allowing officials to provide additional services to anyone forced to evacuate. An entire mobile home park within the city is on evacuation alert.
But with anticipated temperatures of 17 to 18 degrees Celsius later this week, he says things are about to get more difficult.
The mayor adds the situation has been made even worse by the damage of back-to-back record wildfire seasons in 2017 and 2018, which took away vegetation that would have normally absorbed much of that snowmelt.
“When you have a fire in the area and it scorches the ground and there’s nothing top hold it back, once it starts to flow it’s basically ashes flowing and it doesn’t stop,” he said.
City councillor Scott Nelson agrees, and says the damage is going to lead to some massive bills.
“This is a one in 200 year event,” he said. “We’re talking in the magnitude of millions of dollars that this may cost us.”
Nelson says the province has agreed to send emergency funds to the city for mitigation and disaster relief, but he anticipates more will be needed.