SR 401 - 2.3 Miles S. of Bean Creek Bridge - Slope Stabilization

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Needs & benefits

Due to roadway settlement from heavy rainfall, both directions of State Route 401, also known as Lewis and Clark Trail Highway, between the Astoria-Megler Bridge and Naselle are closed. The soil beneath the road near milepost 4.5 is too unstable to allow vehicles safely through and the entire stretch of highway was closed on Tuesday, Feb. 23.

Our geotechnical engineers are gathering extensive information in the field to help determine a long-term fix to stabilize and reopen the highway. However, because of the substantial damage caused to the roadway, long-term repairs will likely take months to complete and there is currently no estimated time for reopening the highway.  

As part of our proactive stabilization efforts, we continually evaluate slopes based on several factors. This section of highway is a known unstable slope, one of many that we track and manage adjacent to state highways. It was recently re-evaluated and ranked near the top of our repair list. If the slope had not suddenly failed, repair work was scheduled in the next couple of years. 

Updates - April 15, 2021: 

Following a thorough evaluation of field data, WSDOT geotechnical engineers have determined that emergency contractor crews can build a temporary bypass road around the damaged section of roadway. 

  • WSDOT hired an emergency contractor, Big River Excavating.
  • Contractor crews cleared debris and finished construction of a temporary bypass road around a damaged section of highway.
    • Travelers will be shifted to use a single lane of travel with temporary signals alternating traffic. 
  • Provided that the adjacent landslide remains stable; the temporary bypass road will stay in place while crews work on long-term repairs to stabilize the slope and repair to the roadway.
  • WSDOT engineers are using data collected over the past few weeks to help design the long-term repair, which is scheduled for construction this summer.

With the opening of the temporary bypass road along SR 401, the Dismal Nitch Rest Area, east of the Astoria-Megler Bridge is now open.

Timeline

  • 1994 - Geotechnical engineers began tracking the unstable slope along SR 401 near milepost 4.5 
  • 2019 - Conceptual design work on a long-term fix began
  • April 5, 2021: Construction of the temporary bypass road begins
  • April 15, 2021: The temporary bypass road was opened up to travelers
  • Spring 2021 - Exploratory and design work continues 
  • Spring 2021 - Construction to stabilize the slope and repair the road is estimated to begin 
  • Late 2021 - Project is scheduled for completion 

Funding 

The cost of this project is estimated at approximately $2 million

Funding

Financial Data for PIN 440123S
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $2,559
CWA $0
Total $2,559

Contact

Joanna Lowrey 
Project Engineer 
(360) 442-1350

Celeste Dimichina 
Communications 
(360) 905-2057

State Route 401 - 2.3 Miles South of Bean Creek Bridge - Slope Stabilization - project location in Pacific County, WA