Nighttime drivers heading in and out of Black Diamond will be seeing some construction and lane closures for the next couple months.

The city is in the first steps of a two-year project to install two roundabouts north of the city near Roberts Drive, which has affected the intersection there since fall of last year.

The first phase of the project was creating an underground stormwater “vault” to treat stormwater and runoff.

With that complete, workers are now replacing a Puget Sound Energy main gas line that runs under the Roberts Drive and the SR 169.

The project started Feb. 25, and work is expected to continue through all of March, though only at night from 7 p.m. to 5 a.m. During work hours, SR 169 will be reduced to one lane.

UPCOMING WORK – ROBERTS DRIVE TO CLOSE

There are a lot of steps between now and when those two roundabouts will finally be constructed in November 2025.

Drivers should be aware that Roberts Drive is expected to close, though not until toward the end of “the end of the school year to lessen the impacts on the school routes and traffic,” said Black Diamond Master Plan Development Team Director Andy Williamson.

He added that it’s unclear how long the road will be closed for, but drivers will likely need to use Baker Street to get around the closure; truckers are to use 288th.

The city aims for this to be the only road closure during the overall project — other work is expected to continue to take place at night, with alternating lane reductions.

WSDOT FISH CULVERT

In addition to the roundabout project, the Washington State Department of Transportation is expected to swoop in and construct two fish culverts under SR 169 — one at Black Diamond-Ravensdale Road (Ginder Creek) and the other under SR 169 at Jones Lake (Rock Creek), which is the body of water located to the west just outside the city’s southern limits.

If you thought the two-year roundabout construction was long, hold onto your salmon, because WSDOT is expected to work on these projects for five years, into 2029.

According to WSDOT Communications Manager Eric Zackula, the project is not yet fully designed, and will be completed once the state awards the project to a contractor; bidding for the project began in January, and a contractor is expected to be announced in July.

A construction timeline is also not complete, as a contractor can choose to begin working on SR 169 or SR 509 (which is also getting a new culvert) simultaneously or separately. However, Zackula said the work on Rock Creek has to be complete by December 2027.

Work on Ginder Creek can’t start until the roundabout project is complete.

Finally — surprise, surprise — traffic impacts are also unknown, but Zackula said WSDOT has “an eye” on commuters and is giving potential contractors wide berth to do their work in a way that could affect traffic less.

Zackula added that this is not just a culvert project, but an environmental restoration effort; by the end of construction, there will 4.5 miles of new habitat for coho and chum salmon, as well as trout.

“It’s going to be a really good environmental impact,” he said. “… We’re sort of proud of that.”

WSDOT is required to construct and restore culverts across the state due to a 2013 Washington State District Court injunction that ruled the state has a treaty-based duty with Native American tribes to preserve and improve fish runs.

Since then, the department has worked on 114 culverts and improved over 500 miles of habitat, Zackula said.

Two roundabouts are being built in Black Diamond, but that comes with lane reductions, including the one on SR 169 happening now through March. Image courtesy the city of Black Diamond