Road construction this weekend will close two lanes of northbound I-5 entering Seattle, close southbound Highway 99 over the waterfront, and block a lane for three miles of westbound I-90 near Cle Elum.

Share story

Road construction this weekend will close two lanes of northbound Interstate 5 entering Seattle, and close southbound Highway 99 near the waterfront. A night closure will disrupt trucking on Highway 18.

But in an unusual lane gain for downtown Seattle drivers, the state will open a new four-lane Alaskan Way surface street on Sunday morning.

In addition, the state said late Thursday it can reopen both lanes of westbound I-90 near Cle Elum for weekend travel, before closing the right lane again next week. Repairs are ongoing there from mileposts 90 to 87, where crews are grinding new grooves into a slippery downhill section of freeway there.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, CenturyLink, Kemper Development Co., NHL Seattle, PEMCO Mutual Insurance Company and Seattle Children’s hospital. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

Learn more about Traffic Lab » | Follow us on Twitter »

Here are three sites where lanes will close:

  • This year’s last big weekend of “Revive I-5” deck repairs will block two northbound freeway lanes from the south city limits to Olive Way downtown. Closures depend on dry weather and are scheduled from 8 p.m. Friday until 5 a.m. Monday. Crews are replacing expansion joints and broken concrete panels built in the mid-1960s.
  • The southbound lanes of the Alaskan Way Viaduct will close all weekend from the south end of the Battery Street Tunnel to Spokane Street, from 9 p.m. Friday until 5 a.m. Monday. This will enable contractors to set concrete for the future interchange from the waterfront streets into southbound Highway 99, when the four-lane tunnel opens in February.
  • Westbound Highway 18 will close from the I-90 junction for 7.6 miles to Issaquah-Hobart Road, overnight from 9 p.m. Sunday to 5 a.m. Monday, the state said in a freight alert.

In the Seattle area, transportation officials urge travelers to reschedule their trips to avoid congestion, or use Sound Transit light rail, which is back to speed in Tukwila after cracked rails were replaced last weekend.

Now about those waterfront lanes: The Washington State Department of Transportation will move its two-lane detour street out from under the viaduct into a new, asphalt four-lane Alaskan Way.

The new road connects to 12 downtown intersections and will serve traffic until a bigger permanent boulevard (ranging from four to nine lanes) and new bridges from the waterfront to Belltown are built. As workers make the shift, Alaskan Way will be closed from 8 p.m. Saturday to 10 a.m. Sunday, between the ferry terminal entrance and Wall Street. During the detours, viaduct buses including the C and 120 routes will return to West Seattle and Burien by entering southbound I-5 at James Street, followed two miles later by a right turn at the West Seattle Bridge off-ramp.

Ferry customers will continue to walk on at the Marion Street pedestrian bridge, or drive on through South Jackson Street.

Space under the viaduct will revert to parking and a slow access lane — as existed for decades before work began to build a city seawall and dig the Highway 99 tunnel that opens in February. Parking will increase by about 70 spaces, the state said.

The four-lane surface road will be crimped to a two-lane bottleneck at either end. To the north, the city’s rebuild of the wooden Pier 62 will consume two lanes, while at the south drivers will cruise through the two-lane stretch of diagonal Railroad Avenue South to reach the ferry terminal or waterfront.

For several months next year, demolition of the old viaduct will reduce the four-lane roadbed to two lanes, as the contractors move about the area.