(briefing is over – coverage below, posted as it happened)

We’re on the fourth floor of the World Trade Center West, across the street from Bell Street Pier. The Stakeholders Advisory Committee members were briefed on the tunnel plan a bit earlier; right now, before the governor, county executive, mayor, and port CEO make the official announcement, it’s something of a party atmosphere, with officials of the various governments mingling with committee members, media, and others:

Outside, along Alaskan Way (not far from the TV trucks) – a handful of pro-elevated, anti-tunnel demonstrators with “No Big Dig” signs.

From the official news release: This is a $4.24 billion plan, which “includes investment in improved bus service, east-west city streets, a new seawall, relocated utilities, and an upgraded waterfront.” The state’s commitment remains $2.8 billion. The city, the release says, will spend $930 million to “replace the central seawall and construct a waterfront promenade, relocate utilities, build a streetcar on First Avenue, and improve east-west streets.” The county “will seek new motor vehicle excise tax authorization from the legislature to fund more than $190 million in transit capital and $15 million annually in operating expenses.” The release adds that the Seattle Port Commission will be asked “to consider a $300 million investment in the replacement of the south mile of the viaduct and a new east-west connection to the container terminals.” Federal funding also is involved. Timeline: Construction to start in 2011, tunnel to be open in 2015. We will add more details as they’re announced during the briefing.

8:46 AM UPDATE: The governor is in the middle of the announcement. She says “This is not a solution for tomorrow, this is a solution for the next hundred years.” She also makes it clear, this is not the same tunnel that went before voters — “this is a new solution.” She says, now is the time to make a decision. No additional details so far beyond what we wrote above. She opened by quipping, “My mother always said good things come to those who wait,” although she later went on to insist that the viaduct project is still on schedule.

8:51 AM UPDATE: Mayor Nickels is speaking now. He says, “The package announced today is a victory” — a victory for the people of the city, county, and state. He also calls it a compromise, and says he had hoped there could have been a solution that would not have required the building of a “new traffic corridor,” but says that turned out not to be possible. The mayor says the 1st Avenue streetcar will go from Pioneer Square to Queen Anne Hill. And he says federal and state help will be pursued “in upholding our end of the bargain.”

8:59 AM UPDATE: County Executive Ron Sims speaks next. He calls this a “very good” proposal and says he is happy that it’s a four-lane solution and not a six-lane one. He is now thanking West Seattle’s County Councilmember — now Council Chair — Dow Constantine for his role in the process. (Photo added later – Constantine and others, mostly Seattle councilmembers, to the right of the podium as the executives’ speeches continued)

Sims says that he, the governor, and mayor had a long and candid conversation in early December. He says that this could increase transit service by 25 percent – one million new service hours. (He has repeated that number many times.)

9:05 AM UPDATE: The three executives have just ceremonially signed an agreement. Photo in a moment. Now the governor is taking questions.

9:09 AM UPDATE: KOMO’s Bryan Johnson says an initiative is to be filed by some opponents of this project and asks what a delay would do to the project. The mayor answers: It would cost millions of dollars a month. He and the governor say “people have the right to voice their opinions” but she says “I will be very disappointed … if we delay this project … Because that viaduct, in my opinion, personally, is not safe, and needs to come down … We are on schedule now and I don’t want to delay it.” She also says, “This is not the same tunnel (people voted against).” And she says Boston’s Big Dig problem was trying to “move the world” to build a tunnel. “We’re going to keep the world in place,” she says. The governor was then asked if the viaduct still will come down in 2012; she says “we’re looking at whether … we leave the viaduct up with restrictions on it (beyond 2012) … One of the virtues of this idea is the lack of disruption to businesses on the waterfront … That’s one of the clear goals that led us to this decision – do not force those businesses on the waterfront out of business.” She says they have “not reached a final conclusion” on when the viaduct will come down.

9:15 AM UPDATE: In response to questions about whether this is the right decision, the basic theme is that the viaduct could come down any time soon — we are overdue for an earthquake. “We are not interested in nature making that decision for us … End this debate. It’s time for this to end. Let’s just move forward,” says county executive Sims. “It’s not going to be easy, it wasn’t easy getting here,” says the governor. “We now turn to the legislature and ask them for help … They must make the appropriation … for moving forward. If we don’t come together and move forward, will we look at ourselves like Minneapolis and ask, where were we, why couldn’t we move forward, and forge the political will to get something done. The day has come, the time is now, let’s go get it done, the people of the state of Washington and their families deserve it.” With a huge round of applause from the onlookers filling the room, that concludes the briefing – the governor says she has to get to Olympia for the legislative session. We will be circulating for reaction; more later.

9:27 AM UPDATE: OK, one more update before we leave the briefing – just talked to County Council Chair Constantine, who says it’s up to state engineers whether they determine the viaduct safe enough to leave up while this is built, but he’s definitely concerned about West Seattleites’ mobility. We also talked about the motor-vehicle tax that is mentioned as the county’s contribution to raise money for more transit – a 1% excise tax, which means that every $10,000 your car is worth, it will cost you $100 a year. The County Council will have to approve it, and he says that it’s always tough to vote for a tax, but that there is a “crying need” for more transit service around the county.

11:08 AM UPDATE: Back at HQ now and will post a followup later with video, more graphics, reaction – First, though, another way in which this might cost you: Heard state Transportation Secretary Paula Hammond talking live with KIRO radio’s Dave Ross as we drove back. She told him that while the state is committed to $2.8 billion, it only has $2.4 billion of that locked down, and the $400 million gap might come from a toll – $2 or less. What happens next all depends on what goes on in the Legislature, so whether you’re for the tunnel or against it, you might consider letting your legislators know how you feel: State Senator Joe McDermott, Rep. Eileen Cody, Rep. Sharon Nelson.

11:34 AM UPDATE: The Alaskan Way Viaduct website is updated with more information – you can follow links from this page, including the map that shows where the tunnel is supposed to start and end, and how it’s supposed to reconnect near Aurora, on the north end. The map also mentions the Delridge RapidRide bus service that will be added as part of the plan, which also was mentioned by stakeholders’ committee member Vlad Oustimovitch of Gatewood; our post-announcement interview with him will be in the followup.