State transportation workers were dangling from ropes on a hillside high above Interstate 5 near Bellingham earlier this week as crews worked to stabilize the slope that collapsed one week ago. No timeline has been announced for reopening the freeway.

The Washington State Department of Transportation said Saturday that weekend work continues, with crews “scaling and placing drilling anchors on [the] slope.” Northbound I-5 remains closed since the landslide March 19.

About 12 million pounds of earth, including boulders the size of buses, came down along a 200-foot swath of I-5 northbound between exits 246 and 250 earlier this month. Three cars were nearly crushed, though concrete barrier walls installed for exactly that scenario absorbed the brunt of the slide. Officials said mirrors and antennas were spotted in the debris, indicating some vehicles were sideswiped by falling trees.

The area is a known slide zone. WSDOT workers, trained in mountaineering and slope climbing, are methodically clearing loose trees and rocks before bolting the hillside back into place.

“We have an unstable slope that we need to stabilize, and the way we do that takes a lot of time,” WSDOT engineer Melissa Ambler said.

Crews are also using drones and geotechnical expertise to pinpoint where rock bolts are needed to keep formations from shifting further.

“We can fly our drones and use our expertise in the geotechnical field to find out where we should bolt rocks to keep them stable,” Ambler said.

Northbound drivers are being detoured onto Chuckanut Drive or Samish Way. Highway 9 remains the only permitted route for freight crossing the Canadian border.

WSDOT said the closure, while disruptive, is also prompting engineers to survey the hillside for additional cracking and remove unstable rock formations before they pose a future hazard.

“We have our geotechnical engineers looking for additional cracking so we can remove those unstable rock formations now so they don’t come down in the future,” Ambler said.

There is no timeline for when I-5 northbound will reopen.