The main route between Wenatchee and Lake Chelan on the west side of the Columbia River will stay closed at least three weeks to stabilize the hazardous hillside, the Washington State Department of Transportation said Friday.
U.S. 97A has been closed since Thursday afternoon when the potential for rockfall from the hillside was deemed too big a danger for motorists.
WSDOT said falling rocks have increased in severity and frequency on the highway south of Knapps Hill Tunnel.
In addition, WSDOT said it “has now also identified larger boulders that have been exposed and undermined by the slides, increasing the likelihood that these rocks will fall on the road.”
Motorists traveling between the Wenatchee Valley and Chelan are being advised to use Highway 97 on the east side of the Columbia River.
State Route 971 – the Navarre Coulee Road – is open to local traffic but is not recommended for large vehicles.
Work was already planned on the hillside next week
Closures were already planned for the highway beginning next Wednesday as a state contractor begins a $660,000 project to remove loose and unstable rocks at three different locations, including the Knapps Hill Tunnel site.
That project was supposed to have started April 6, but WSDOT suspended all its projects after Gov. Jay Inslee issued his Stay Home, Stay Healthy orders March 31 in response to the COVID-19 pandemic.
A Washington State Patrol photo of a rock slide near Knapps Hill Tunnel earlier this week.