Culvert Work Near Twanoh State Park: LATEST

Local access to SR 106 near Twanoh Falls closes Monday night Sept. 16

TWANOH FALLS – From 7 p.m. Monday, Sept. 16, to 7 a.m. Tuesday, Sept. 17, crews working for the Washington State Department of Transportation will close access from both East Twanoh Falls Drive and East Creekside Drive to State Route 106 in Mason County. During the closure, crews will increase the elevation of the highway by five feet to accommodate a 20-foot culvert being installed under the road. Residents who access SR 106 from those two side streets are advised to plan ahead and to park outside of the construction zone if they need to travel on SR 106 during that time.

More information on the culvert project can be found at WSDOT’s project web page.


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WSDOT reduces SR 106 to one lane near Twanoh State Park for culvert work. Motorists traveling along scenic State Route 106 should expect delays up to 15 minutes from early September to mid-October while crews remove and replace a culvert under the highway.

Starting Tuesday, Sept. 3, crews working for the Washington State Department of Transportation will reduce SR 106 to one-way, alternating traffic around the clock near Twanoh State Park, eight miles east of Union. That one lane of traffic will be rerouted onto a temporary, 600-foot-long detour built adjacent to the highway.

The speed limit through the work area has already been reduced to 25 miles per hour. The work area includes the SR 106/Creekside Drive intersection, which provides access to approximately 400 homes. Flaggers will provide around-the-clock traffic control to maintain access to those homes during the seven weeks the detour is in effect.

In those seven weeks, crews will cut through the roadway asphalt to expose and remove the existing three-foot-wide culvert, and replace it with a 20-foot-wide culvert. The new culvert’s substantially increased capacity is expected to reduce the potential for localized roadway flooding, which has been a chronic problem. A side benefit is that the larger culvert will provide an enhanced passageway for fish.

After the new culvert is installed, crews will repave the highway, which will be about six feet higher at the site to accommodate the larger culvert, and restore the previous 40 mile-per-hour speed limit. The project is scheduled to be complete this fall.

WSDOT News Release