As Lake Stevens braces for Costco traffic, Highway 9 gets new roundabout

With construction underway at a new Costco, roads are already changing in Lake Stevens.

As crews get to work, drivers could see some traffic disruptions.

Interwest Construction, Inc., was set Monday to prepare the intersection of Highway 9 and South Lake Stevens Road for a two-lane roundabout. The Washington State Department of Transportation (WSDOT) hired the contractor for the project estimated to cost $8.8 million. The roundabout accounts for about $5.1 million.

Construction is expected to conclude this fall.

“This whole project is really to facilitate changes for the Costco going in,” WSDOT spokesperson Tony Black said.

An average of 18,000 vehicles used the nearby stretch of Highway 9 daily in 2020, WSDOT data shows.

About 800 cars are expected in the area during the peak evening commute near the Costco, according to project documents.

The Costco building is planned to be 160,000 square feet, with over 800 parking spaces and a gas station with 30 pumps. It would occupy the area from 91st Avenue SE east to Highway 9, and from 20th Street SE south to 24th Street SE and South Lake Stevens Road.

In all, the retail space would cover almost 37 acres.

The nearest Costco is in Everett, about 10 miles away via the U.S. 2 trestle and I-5.

As part of its development agreement, the company is building new segments of 91st Avenue SE and 24th Street SE. Both would connect to the store’s parking lot, and the latter links to Highway 9 and the roundabout.

At least two weekend closures are needed for roundabout work. The first is 9 p.m. Friday to 4 a.m. Monday. A detour will take pass-through drivers to U.S. 2, but local access will remain.

Crews will shift traffic to the east side of Highway 9. That lets them start work on the west side and South Lake Stevens Road, which will be closed about eight months. A detour for that access is set for 32nd Street SE and 91st Avenue SE.

The detour for drivers heading through the area goes to Highway 204 or U.S. 2. It could cause backups at the stop sign intersection at 20th Street SE.

Some evening weekday Highway 9 lane closures are expected but have not been scheduled yet.

A state study determined the roundabout was safer than a traffic signal at the South Lake Stevens Road intersection, Black said.

“At a signal, you have the chance of someone trying to run the light,” Black said.

Instead, drivers are expected to slow from the highway’s speed limit of 55 mph to between 25 and 35 mph through the roundabout.

Pedestrians will be able to cross the highway there, too. A crosswalk, with space for pedestrians to wait if necessary, is going in on the north end of the roundabout.

Without crossing signals, roundabouts can be more harrowing for pedestrians, especially those with disabilities.

Larry Watkinson, who works on Americans with Disabilities Act compliance for the Washington State Department of Transportation, said they can be safer with raised crossings, rapid flashing beacons and a vehicle approach that forces slower speeds.

The highway project also includes replacing a culvert under the road for Centennial Creek. The existing corrugated steel pipe culvert is 2½ feet in diameter and 63 feet long, according to a permit application.

It isn’t considered a barrier by the Washington Department of Fish and Wildlife, but it has to be replaced because of impacts from the road project.

The new passage will be 19 feet wide and 6 feet above the water.

That work won’t start until after July 5, in compliance with state fish management rules.

The state also is building a stormwater pond with two cells just west the current intersection. Its overall footprint is about 120 feet by 120 feet.

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