Still sliding

Wet weather keeps Cook Lake slide active

By Sarah Pridgeon

Recent heavy rainfall has caused more movement than anticipated on the active landslide at the Cook Lake recreation area, says Acting District Ranger Brian Karchut. Work is underway to evaluate just how much the hillside has slipped and the potential for further activity.

Cook Lake has been closed for the last year amid concerns that one of the largest landslides in the Black Hills is located just above the lake and could, if triggered, run at devastating velocity across the water and into the Loop A campground.

This summer, a team headed by Karl Emanuel, North Zone Geologist for the Black Hills National Forest, including a group of students from the Colorado School of Mines, has been performing geotechnical studies in the hope of identifying the fail point of the landslide and how close the hillside is to liquefying.

“There has been some movement – they’re actually out there today with some students from the School of Mines,” said Karchut on Tuesday.

“They’re taking another look and getting some more research underway, starting today.”

Whether the movement will change how the geotechnical study needs to be performed is unknown at the present time, says Karchut.

Measurements taken recently show that the hillside has slipped “substantially” more than expected, he continues. It is assumed at this point that the excess rainfall experienced across Crook County this summer is responsible for the movement.

“They’re refocusing their research with these students right now to figure out exactly where it’s moving and what the potential is,” he said.

The results of the study are expected to be complete in the fall. Despite the additional movement and unexpected conditions, says Karchut, it appears at present that this timeline remains on track.

“We’ll know more after they take a look,” he said.

In the meantime, the recreation site remains closed to the public for reasons of safety.

“The order is still going to be in effect. It went in on I think May 9 and it goes for a year,” said Karchut.

“Until we get some more substantial research completed, it will stay closed.”