Glenda Pearson, a University of Washington librarian, already rises at an ungodly hour to feed her many animals before making her long commute via a vanpool to Seattle.

Next week, however, when the Alaskan Way Viaduct shuts down for a little more than a week, the Vashon woman is braced for an even earlier start to her day — rising at 3:15 a.m. instead of 3:30. The goal, she said, is to get her vanpool onto the 6:25 a.m. walk-on-only boat, which allows two vans to board, instead of the 6:40 a.m. boat the van usually catches.

But even with an earlier start, she’s expecting a tough commute. Asked what she thinks her daily trek into Seattle will be like for those nine days when the viaduct closes, she answered in a word: “A nightmare,” she said.

“Our major concern is that some people have to be on campus by a certain time, and that won’t be possible, we don’t think,” she said.

The viaduct’s closure from 7:30 p.m. Oct. 21 until 5 a.m. Oct. 31 will mark the longest shutdown of a Seattle-area highway in the state’s history, traffic officials say. And many, like Pearson, are expecting the worst.

The Seattle region is already heavily congested during commute hours. Add the 110,000 drivers who will be displaced by the closure of the north-south arterial along Seattle’s waterfront, traffic experts say, and the result will likely be several days of the toughest commute in the region’s history — especially at the beginning, before commuters find their way through a maze of alternative routes.

“I know for a fact that the first day of the closure is going to be real tough,” said County Councilman Joe McDermott, who chairs the King County Ferry District.

For Vashon, the impact could be particularly significant, in large part because West Seattle — Vashon’s portal to the mainland — is expected to be ground zero in viaduct-related traffic snarls. Even the passenger-only boat from Vashon to Seattle will feel the impact, some say, as Islanders who normally get to Seattle via West Seattle opt to ride the daily commuter boat.

“I think we’re going to be hit hard,” said Kari Ulatoski, a ferry-service advocate who pays close attention to traffic issues. “And not just during rush hour. I think it’s going to be challenging to participate in any event where we have to go east and into Seattle.”

“Everybody is going to have to be very patient,” she added.

King County Metro and the ferry district are trying to compensate for the closures, adding service directed in large part toward easing the West Seattle commute. Enhanced service includes:

• increased sailings on the West Seattle water taxi into downtown Seattle, as well as more parking spaces at the West Seattle dock and along Harbor Avenue S.W.

• increased service by Metro’s West Seattle shuttle — routes 773 and 775 — which takes riders from various stops in West Seattle to the water taxi’s dock at Seacrest Park.

• more frequent service by Metro Route 54, which has already been implemented and which is scheduled for departures every 15 minutes rather than every 30 minutes.

But despite some requests from Vashon residents, the King County Ferry District decided not to increase the number of Vashon-Seattle water taxi sailings, McDermott said.

Already, he noted, the schedule is “maximized,” with the boat turning around quickly to make its three morning runs and its three evening runs. An additional sailing would have gotten commuters into Seattle around 10 a.m., too late for most workers, he said.

The ferry district’s board considered the possibility of renting an additional boat, but set aside that idea because of costs, McDermott said; an additional boat would have cost the cash-strapped ferry district $15,000 a week.

Like Ulatoski, he believes the pedestrian-only boat will be particularly crowded during the viaduct closure, and more passengers than usual, he predicted, will get left on the dock.

“The Vashon run is already a very popular run,” he said.

But McDermott, like many of the region’s policymakers and traffic engineers, hopes commuters will be creative and find alternative paths to their daily destinations. Some might cycle; others might find they can work at home; some might be able to compress their work week into fewer, longer days.

“I anticipate more people will be looking for all kinds of commuting options,” he said.

The closure is the first tangible step in the state’s $2 billion plan to replace the aging and vulnerable viaduct with a bored tunnel beneath downtown Seattle, a project that got its final green light in August, after Seattle voters, in an advisory vote, OK’d the project.

During the nine-day closure, workers will demolish vast sections of the southern mile of the viaduct and complete a temporary four-lane detour that will connect a new southbound bridge to the central waterfront section of the viaduct. The detour will be in place until late 2015 or so, when the tunnel project is slated to be completed.

The closure is the only one expected during the course of the ambitious tunnel project, except at the project’s completion, when the viaduct will be shut down for up to three weeks to connect the bridges to the finished tunnel, said Ka Deena Yerkan, a spokesperson for the state Department of Transportation.

“That’s great news,” she said.

But once the detour is opened on Oct. 31, commute patterns will continue to be affected — as the new route will have a posted speed limit of 25 mph, down from 40 mph currently, Yerkan said.

“The detour will slow people down,” she said.

McDermott, however, said he believes commuters will find ways to live with the detour over the next couple of years, and eventually, the impact will lessen.

“The first day that detour opens, it’ll be slow-going,” he predicted. “Some people will get used to it and keep driving it. Others will find new routes. There will be a norming period as we learn to live with it.”

News on the closure: Viaduct replacement project leader to visit Vashon

Matt Preedy, deputy director of the Alaskan Way Viaduct Replacement Program, will attend a meeting of the Vashon-Maury Island Community Council at 7 p.m. Monday, Oct. 17. Preedy will discuss the detour that the state Department of Transportation is building and that will be in place for the next four years or so and its impact on Vashon commuters. The meeting will be held at McMurray Middle School.

The state and county have extensive information about the nine-day closure, including a simulated driving video that can be found by going to www.youtube.com/watch?v=W0aaX8s3MME. And to help commuters plan transit options, Metro has set up a new website at www.kingcounty.gov/getyouthere.

Meanwhile, the state Department of Transportation is holding what it’s calling its “One Last Shot” public contest. The winner and 24 of his or her friends will receive access to the viaduct’s downtown section for 30 minutes on Saturday, Oct. 22, by answering the question, “What would I do with 30 minutes on the Alaskan Way Viaduct?” Play soccer? Propose to your significant other? Hold a dance? Submit an answer in 100 words or less to viaduct@wsdot.wa.gov by Sunday, Oct. 16. The person who is selected and his or her collection of friends will be escorted to a private section of the viaduct to follow through on the winning proposal.