SR4 closure may extend for weeks or months

Published 12:43 pm Monday, January 27, 2020

SKAMOKAWA — The highway between Naselle and Longview will remain closed “for an indeterminate amount of time” following a large landslide Jan. 23, state highway officials said Jan. 28.

The slide near KM Mountain’s eastern base followed several days of intense rainfall, including seven inches during one 24-hour period. Nearby Naselle’s January rainfall total will exceed 30 inches. Last week’s deluge resulted in significant flooding, several other landslides and a power outage caused by downed trees in Wahkiakum County. A less severe slide continues to block a lane of U.S. Highway 101 near Raymond.

The slide at about milepost 25.5 on State Route 4 involves mature trees, rocks and mud. The highway is impassible and closed to all but local traffic from milepost 19 near Shannon Road to milepost 26 near Mullen Road.

“The hillside is actively moving and too unstable and saturated from heavy rainfall to safely clear and reopen the highway at this time,” the Washington State Department of Transportation said in a Jan. 24 press release.

WSDOT does not know when the highway will reopen. It could be weeks or months, agency spokeswoman Tamara Greenwell said Jan. 28.

“We want to begin cleanup and repair work as soon as possible,” said WSDOT project engineer Joanna Lowrey. “Once we can safely get crews into the area, we’ll have a clearer picture of the extent of the work and when we can reopen the highway.”

On Jan. 27, in preparation for work to begin, WSDOT awarded an emergency repair contract to Nutter Corporation. Contractor crews are developing a plan to safely remove large fallen trees from the unstable slope and planned to move equipment to the slide location on Jan. 28.

This work is the first step in a long process to clean up debris, the agency said. How complex this job will be and how long it will take will depend on what engineers find after the fallen trees are carefully removed, Greenwall said.

WSDOT engineering geologists are analyzing video of the slide captured with drone technology to develop a long-term fix to stabilize the hillside.

The highway over KM Mountain crosses through terrain that is notoriously prone to slipping. This current landslide is downhill from a massive slide that closed the highway for months in the early 1990s. That closure went on for so long that a detour on narrow logging roads was paved. Businesses in Naselle, partly dependent on tourism traffic between Longview and the coast, were impacted.

At present, logging roads around the slide remain gated and unavailable for a detour. The existing option is U.S. Highway 30 on the Oregon side, accessible via the Longview and Astoria-Megler bridges. In addition, the ferry Oscar B. between Puget Island and Westport, Oregon is operating free of charge around the clock. It leaves the Washington side on the hour and the Oregon side on the quarter after.

Status updates on the closure are available at www.wsdot.com/traffic. Drone video of the slide is available at https://tinyurl.com/SR4-landslide-video.