Spokane Street will be closed to eastbound traffic starting Monday, Sept. 8 - the first of a series of construction projects disrupting traffic from now until the Alaskan Way Viaduct is replaced starting in 2012.

Lower South Spokane Street, the surface road, will be closed between First Avenue South and Fifth. Access to local businesses will be allowed only between First and Second avenues.

The upper Spokane Street Viaduct will be open to regular traffic.

Traffic on the surface from Harbor Island must detour north on East Marginal Way, east on Hanford Street, to First Avenue.

Commuters driving east on the West Seattle Bridge may still exit at First Avenue, but must turn left at the bottom of the ramp. Shoppers heading to Costco must drive north to Lander Street and east to Fourth Avenue, before heading south.

No parking will be allowed under the Spokane Street Viaduct between Second and Fifth avenues. The area will be used for storing and staging construction materials.

Seattle Public Utilities has contracted the construction company Scarcella Brothers Construction to replace a 30-inch main, which provides water to West Seattle from the Beacon Hill reservoir. Columns for a new eastbound off ramp to Fourth Avenue will be built where the pipe lies.

The pipe needs to be replaced. This section of the water main is a hundred years old, made from cast iron pipe with poured lead joints.

"It was our opportunity to bite the bullet and do that part of the project right," said Gavin Patterson, the project manager with Seattle Public Utilities.

The new steel pipe will be laid 10 feet parallel to the south, allowing the old main to supply water during construction of the new one.

The new pipe will be less vulnerable to vibration from viaduct construction and earthquakes.

Other work begins this week to connect two dead-end pipes in the area. A 24-inch water main branches to the south on Second Avenue, the only pipe supplying water to Charlie's Produce. This main will be connected to a 12-inch pipe, another dead-end on South Dakota Street from a main on First Avenue. This will supply water to Charlie's Produce while the main on Spokane Street is shut off during construction.

Though the contracted deadline for moving the water main is Nov. 20, this section of Spokane Street will be closed through mid-2010. The replacement of the main is the first in a linked series of transportation projects.

The water main must be moved before the eastbound Fourth Avenue exit can be built, starting in 2009.

A second structure will be built north of the Spokane Street Viaduct between I-5 and SR-99, widening the viaduct from four to six lanes. Westbound lanes of lower Spokane Street will be closed during this construction.

The new exits to First and Fourth avenues are scheduled to be completed by 2011.

The increased capacity of the Spokane Street Viaduct will ease traffic during construction of the new south end of the Alaskan Way Viaduct. Its construction also begins in 2009 with lane closures starting in 2010.

New entrances and exits from the south end of Alaskan Way in the SoDo area must be completed before the state demolishes the central waterfront section of the viaduct, as Governor Chris Gregoire promised, in 2012.

Matthew G. Miller is a freelance writer living in the Admiral District. He may be contacted through wseditor@robinsonnews.com.