Weeklong closure of Cosi Hill begins on Monday

Drivers will be sent through Blue Slough and SR 107 around the construction next week as temporary lanes are constructed in preparation for a 2 year project.

The Washington State Department of Transportation encourages drivers to plan ahead for a five-day, total closure of US 101 at Cosi Hill to all traffic from 6 a.m. Monday, June 17 to 6 p.m. Friday, June 21.

Weather permitting, this work allows contractor crews working with Rognlin’s Inc. to construct temporary lanes around the a slide-prone section of US 101 near milepost 78.

The closure will not impede traffic to Highland Golf Course and WSDOT will accommodate first responders through the work zone.

During the closure, travelers will follow a 7.5 mile detour via State Route 107 and Blue Slough Road.

• The intersection of SR 107 to northbound US 101 will close to traffic. Northbound US 101 drivers will detour using SR 107.
• Southbound US 101 drivers out of Aberdeen will detour using Blue Slough Road. Access to and from the Highlands Golf Course entrance will be maintained.

Once US 101 reopens, traffic will see narrowed and shifted lanes through the work zone.

For the project, crews will stabilize the slope of the US 101 hillside, repairing the site after a large, slow-moving landslide under the highway has sloughed away portions of the roadway. Repeated slides near milepost 79 have brought repeated road closures. Since December of 2015, the speed limit has been reduced in the area.

WSDOT said, “…maintenance crews have repeatedly patched the roadway through the area, but additional geotechnical earthwork is required for more permanent repairs. Those temporary fixes have proven to only last until the next heavy rainstorm hits.”

The goal of the project would be to reduce the risk of earth movement that could lead to unexpected roadway closures.

Rognlin’s, Inc. crews are set to begin drilling 6-foot-diameter columns nearly 50 feet deep. The columns will be filled with rock to dramatically stabilize this stretch of highway. About 600 shafts will form a buttress to support the roadway.

According to WSDOT, “The rock-filled shafts will help securely hold the hillside in place, reducing the potential for the roadway pavement to move.“

Crews will reconstruct and repave the roadway once the hill is stabilized.

Drivers will encounter shifted lanes and reduced speeds until late fall 2020 during this two-year construction project.