press release:
The contractor working for the Seattle Department of Transportation on the Spokane Street Viaduct (the elevated roadway between the West Seattle Bridge and I-5) Widening Project will institute another round of closures next week. The Spokane Street Viaduct will be closed to all westbound traffic on Thursday and Friday nights, and First Avenue S will be closed at S Spokane Street at night Monday through Thursday.

In addition, motorists in the area will experience a permanent shift in the path for northbound traffic on East Marginal Way moving through the intersection at S Spokane Street when they are shifted onto the new East Marginal Way Grade Separation structure.

The roadway closure impacting the largest number of motorists will occur Thursday, March 15, and Friday, March 16 when the westbound lanes of the Spokane Street Viaduct between I-5 and SR 99 will be closed both nights from 10 p.m. until 5 a.m. the following morning. This will close direct access to West Seattle via the Spokane Street Viaduct from both northbound and southbound I-5. (Motorists traveling southbound on SR 99 will still be able to access the off-ramp to the West Seattle Bridge.)

During this nighttime closure of the westbound lanes of the Spokane Street Viaduct, southbound traffic from I-5 wishing to reach West Seattle can detour by exiting I-5 at S Forest Street, turning right (northbound) onto Sixth Avenue S, then turning left (westbound) onto S Lander Street, turning left again (southbound) at First Avenue S, then turning right (westbound) at S Hanford, turning left onto E Marginal Way S, and finally turning right (westbound) onto the lower S Spokane Street roadway and across the swing bridge into West Seattle. Northbound traffic from I-5 wishing to travel to West Seattle should exit the freeway at the Sixth Avenue S off-ramp, and then follow the same detour route outlined above. Detour signs will help motorists follow the designated route.

Permanent Traffic Movement Change Beginning Monday, March 12 (see graphic)
By Monday morning, March 12 (perhaps earlier), northbound traffic on East Marginal Way S wishing to travel through the intersection at S Spokane Street will instead travel northbound via the newly completed East Marginal Way Grade Separation structure. This project elevates East Marginal Way over the railroad tracks.

Monday, March 12 – Thursday, March 15
First Avenue S at the intersection with S Spokane Street will be closed each night from 9 p.m. until 5 a.m. the following morning. Northbound traffic will be detoured via lower S Spokane Street to Fourth Avenue S. Southbound traffic will be detoured west at S Hanford Street. The First Avenue S off-ramp from the Spokane Street Viaduct will remain open.