Carlsborg drivers can expect road delays starting Monday, July 31, tentatively through late September as construction begins to replace a culvert under U.S. Highway 101 for Matriotti Creek.

The $2.728 million project replaces a 5-foot wide steel culvert from the 1950s with a 10-foot by 19-foot box culvert to open upwards of 5 miles of fish habitat, report officials with Washington State Department of Transportation.

It’s one of 996 culverts under roadways that the Department of Transportation must replace following a 2013 U.S. District Court order following 21 Washington tribes’ request to preserve fish runs by repairing or replacing culverts that act as a barrier to salmon migration.

Shari King, spokesman for Washington State Department of Transportation, said Interwest Construction Inc. will reduce speeds to 40 mph through the construction zone for about half-a-mile around the clock.

All traffic will be diverted to the eastbound lane with one lane for each direction and once the northbound culvert is replaced traffic will alternate to the westbound lane, King said.

Two separate traffic shifts will occur during the project, she said.

“This work goes a long way to help open stream access for fish habitat,” said Project Engineer Chris Bruning for the Department of Transportation.

“At the same time, replacing culverts means closing lanes and detouring traffic, and we understand this will be an inconvenience.”

Department of Transportation officials said the project must be done during the seasonal “fish window,” an environmentally-permitted time frame that reduces construction-related impacts to fish.

Once the project is complete, fish will be able to pass through this portion of the creek easier as the water will be slower and the structure will span a more natural creek environment, King said.

Jamestown S’Klallam Tribe officials previously reported that Matriotti Creek is home to steelhead, a threatened species, coho salmon, cutthroat trout and sometimes chum and pink salmon along with other non-salmonids like lampreys.

Along with fish passage, King said the project helps preserve the integrity of the highway and reduce maintenance costs by reducing or eliminating the possibility of the blockages.

This project follows another project in Sequim Bay State Park where a $1.25 million bridge, now called Sequim Bay Bridge, was installed in May as part of the federal injunction, too. A 3-foot culvert was deemed harmful for fish passage in an unnamed creek, so crews removed it and installed the 210-foot bridge, which connects the Olympic Discovery Trail.

Department of Transportation officials ask drivers to plan ahead for construction.

Crews for Clallam County also have closed a portion of Old Olympic Highway about 4 miles away to replace the McDonald Creek bridge.

For more information on the project, visit www.wsdot.wa.gov/Projects/US101/MatriottiCrkRmvFishBarrier.

Reach Matthew Nash at mnash@sequimgazette.com.