The state Department of Transportation started culvert replacement work on U.S. Highway 12 west of the Montesano exit. Drivers can expect round-the-clock lane closures through the summer.

Traffic will be limited to one lane in each direction. The work is expected to continue into fall.

“The speed limit will be lowered to 25 mph through the work zone,” WSDOT spokeswoman Tina Werner said. Regular travelers of U.S. 12 might wonder why the speed will be so low when similar lane restrictions east of Montesano only have a speed limit of 45 mph.

It’s because of the shorter space to build the crossover, Werner said in an email. “Because of this limited area, the crossover on this project is shorter with sharper curves.”

The WSDOT is replacing a fish culvert under U.S. 12 that is restricting fish passage with a “220-foot-long concrete box structure that will open (almost) 2 miles of potential fish habitat,” according to a WSDOT release.

The state Department of Fish and Wildlife identified coho (Oncorhynchus kisutch) and coastal cutthroat (Oncorhynchus clarki clarki) as two of the species that will benefit most from the reopened upstream habitat.

Another project like this isn’t expected for some time, Werner said.

“After this U.S. 12 culvert work, we do not anticipate having a fish barrier removal project in Grays Harbor county for the next several years,” Werner said. “However, this could change as we are continually looking at prioritizing these types of barriers to match the current available funding.

“Grays Harbor county residents and travelers will be pleased to know that we are on track to wrap up a larger fish passage job in McCleary at state Route 8 Middle and East Forks Wildcat Creek by spring.”