(Water Taxi’s West Seattle vessel Doc Maynard at downtown dock, expecting lots of riders during the closure)

11:49 AM: Just wrapped up on the King County Water Taxi dock downtown: One last media megabriefing before the Alaskan Way Viaduct’s two-weeks-or-so closure, now a little over 10 hours away (onramp closures start at 10 pm, so don’t count on using The Viaduct after that). Those on hand for brief statements followed by Q&A included Dave Sowers from WSDOT, Jon Layzer from SDOT, Paul Brodeur from the King County Marine Division (Water Taxi), Victor Obeso from Metro, Bruce Gray from Sound Transit, and Peter McGraw from the Port of Seattle.

We have it all on video and will upload as soon as we’re back at HQ (1:45 pm update – here it is):

Nothing dramatic but a few points of interest we hadn’t heard much about before:

*SDOT mentioned that the “maritime community” has indeed been asked to try to minimize bridge openings during the closure, but as Layzer acknowledged on our followup question, all they can do is ask – maritime use has priority, particularly for the West Seattle “low bridge” (formally the S. Spokane St. Swing Bridge) – UPDATE: Here’s what SDOT is asking the Coast Guard about, for bridges including ours:

The Seattle Department of Transportation would like to request that the US Coast Guard send out a notice to mariners requesting voluntary compliance at each of the following bridges for the period of 12:01 am on April 29, 2016 to 11:59 pm on May 12, 2016:

Ballard Bridge: Weekday voluntary compliance one hour before and one hour after the existing restrictions (i.e. In addition to the existing restrictions, 7-9 am and 4-6 pm weekdays, we are asking for mariners to try and limit the number of bridge openings between 6-7 am, 9-10 am, 3-4 pm & 6-7 pm, whenever possible).

Fremont Bridge: Weekday voluntary compliance one hour before and one hour after the existing restrictions (i.e. In addition to the existing restrictions, 7-9 am and 4-6pm weekdays, we are asking for mariners to try and limit the number of bridge openings between 6-7 am, 9-10 am, 3-4 pm & 6-7 pm, whenever possible).

University Bridge: Weekday voluntary compliance one hour before and one hour after the existing restrictions (i.e. In addition to the existing restrictions, 7-9 am and 4-6pm weekdays, we are asking for mariners to try and limit the number of bridge openings between 6-7 am, 9-10 am, 3-4 pm & 6-7 pm, whenever possible).

Lower Spokane Street Swing Bridge: Weekday voluntary compliance between 6-10 am and 3-7 pm (there are no existing restrictions on this bridge).

*A temporary stop is being added so that WS bus riders can connect to light rail in SODO – it’s marked on the reroute maps (second page of this PDF shows the West Seattle routes)

*If you want to connect to light rail, the Water Taxi is also an option, it was pointed out to us in conversation with the Marine Division reps after the briefing, since you can walk a few blocks east and get to the transit tunnel (King Street Station, also served by Sounder rail, isn’t far either)

*We asked what happens when they get word that the tunneling machine has made it the full 385-foot distance beneath The Viaduct, to the other side. Sowers says WSDOT would then do one more inspection of The Viaduct, along the lines of what they do twice a year, to check it thoroughly for cracks, settling, etc., before deeming it safe to reopen for traffic.

More to come when we’re back at HQ.

1:45 PM UPDATE: We’ve added the briefing video above. Also, since the briefing, WSDOT has added an online update with yet another reminder plus some news that wasn’t part of the briefing. See the full update here; below, the sections that followed the general reminder:

Seattle Tunnel Partners tunneling operations

Seattle Tunnel Partners is making final preparations for their tunnel drive beneath the viaduct. They have told us that the overnight crew will spend the early hours of Friday restarting and testing Bertha, the SR 99 tunneling machine. Tunneling is expected to begin sometime during the day shift on Friday.

STP expects to start slowly as Bertha digs out of her planned maintenance stop, which is essentially a block of concrete buried in the ground near Yesler Way. The machine must dig through approximately 10 feet of concrete to exit the maintenance stop and enter the soil near the intersection of Yesler and Alaskan Way. Initially, trucks will carry away the excavated material. Crews intend to proceed deliberately throughout the weekend, carefully monitoring the machine’s performance and the surrounding ground as Bertha inches forward.

STP expects to pick up speed early next week. The tunneling operation – tunneling forward, building rings and doing maintenance on the machine – will continue around the clock throughout the closure.

You can track Bertha’s tunneling progress here. We’ll be updating the progress graphic twice each day.

Barging operations to resume

The suspension for cause that has restricted barging operations since January was lifted this week. That means that STP will be allowed to remove excavated soil from the work site via barge using new procedures they developed over the past two months. Having the barging operation back online allows STP to remove excavated material more quickly than trucking the material offsite.

Check out our construction cameras page to get a closer look at the barging operation when tunneling begins on Friday.

Again, we’ll have an update when the closure begins late tonight, as well as expanded coverage of morning and afternoon/evening traffic/transit starting Friday.

With just one day left until the two-weeks-or-so Alaskan Way Viaduct closure starts, a precautionary closure while the tunneling machine goes under the structure, a few points to mention/reiterate tonight:

*WSDOT says the onramps will “start closing” at 10 pm Thursday night. Having driven on The Viaduct to and from a meeting north of downtown in the past few hours, we can confirm that the signage we saw at ramps tonight all carried that message, as does the official infopage at 99closure.org.

*10 pm Thursday night is also when Metro says its rerouting will begin. (See the maps here.)

*The closure is expected to be in full effect by midnight Thursday night. (Some messaging says 11:59 pm Thursday, some says 12:01 am Friday, but basically, it’s midnight tomorrow night.)

*Surface streets/sidewalks/paths under The Viaduct are expected to remain open.

*WSDOT says it’s expecting to update its “tunneling progress” webpage around 11 am and 8 pm weekdays, 2:30 pm weekends, during the closure. Its contractor plans to tunnel 24/7 while going under The Viaduct. But, as photojournalists were told during Monday’s tunnel photo-op, it’ll be slow going at the start.

*If you still have a question, it might be answered on WSDOT’s FAQ page. If not, please comment, and we’ll chase down an answer (reps of every agency involved, and then some, are having another megabriefing tomorrow morning).

(WSB photos by Christopher Boffoli)

Before the Highway 99 tunneling machine starts its dive beneath the Alaskan Way Viaduct, closing it for two weeks or so starting early Friday, WSDOT gave local news media one more chance for a look inside what’s been done so far. Christopher Boffoli was there for WSB.

Monday afternoon’s hour-long tour was his first visit to the tunnel in more than a year and a half, since September 2014 (see his report here), nine months after the machine stalled (eventually restarting just before last Christmas).

This time, tour participants were NOT taken up to the tunneling machine, which has gone 1,560 feet so far.

The trip to get beneath and clear of the Alaskan Way Viaduct will be almost exactly a fourth of that distance, 385 feet.

While WSDOT promises online progress reports at least once a day once the tunneling machine is on its way, it also is warning not to expect much at the start – the one-sheet given to those on today’s news-media tour says contractor Seattle Tunnel Partners told WSDOT that “mining will be SLOW at first” as the first 10 feet will go through the protective concrete block built at “Safe Haven 3” where the machine has been stopped for six weeks.

More tunnel facts: 232 tunnel rings, each weighing 10 tons, are installed so far; reaching the end of the planned tunnel route will require about 1,450 of those rings.

Christopher says today’s tour “was much more limited than the last one” (the September 2014 tour mentions above) – “this time we were simply walked down to the end of the tunnel and taken about midway under the machine (into the area where all of the trailing gear brings the concrete sections forward for placement) and then were walked back out.”

By the way, WSDOT has completed 400 feet of roadway inside the 1,560 feet of tunnel that’s done so far.

We don’t know yet exactly what time The Viaduct will be shut down on Friday morning – WSDOT says it depends on when Seattle Tunnel Partners are ready to start up the machine. But the plan is for it to be long before the morning commute. If you still haven’t figured out how you’re going to get around without The Viaduct, find all the closure-related info at 99closure.org.

(WSB photo: From left, Metro’s Victor Obeso, KC Marine Division’s Paul Brodeur, WSDOT’s David Sowers, SDOT’s Jon Layzer)

11:55 AM: We’ve just left the downtown waterfront, where media reps were invited to an update and Q&A with city, county (Metro and Water Taxi), and state transportation reps on the first weekday since the big announcement that the Alaskan Way Viaduct tunneling-related closure will start April 29th. We recorded it all on video that we’ll add here when uploaded (12:54 pm update – here it is):

(Also), here are a few toplines beyond what we and others already have reported:

*Extra Water Taxi parking: The biggest added temporary lot off Harbor Avenue will be Pier 2, with its entry across from the 7-11 in the 2400 block of Harbor and room for 200+ cars. It will be open for vehicle entry/exit 5:45 am-9:15 am weekday mornings and 4 pm-7:15 pm afternoon/evenings – it’s a secured lot so at midday, it’ll be closed and you won’t be able to get to your vehicle, so it’s not a good choice unless you are headed out for a full workday. It’s also expected that 120 cars will be able to park along Harbor south of Seacrest, on the water side, because of temporary overnight parking restrictions. And about 40 spaces will be available on the SW Bronson Way street end south of Salty’s on Alki (WSB sponsor).

*Larger Water Taxi shuttles: In addition to a special shuttle that will run continuously during those hours between the Pier 2 parking lot and Seacrest, the WT shuttle buses on routes 773 and 775 will be upsized to 39-passenger buses.

*Speaking of Water Taxi shuttles: A commenter had asked why the Morgan Junction leg of the route is only at midday. The King County Marine Division says that’s the only time of day they can run it because of the gap between Water Taxi runs from Seacrest.

*Special Viaduct-closure-related brochure with West Seattle Water Taxi-specific info: See it here.

*In case more buses are needed: Metro will have 11 more buses with 22 scheduled operator shifts, and a potential of 135 added hours, depending on how things go.

*UberHop: This new vanpool-type alternative will have a pickup/dropoff point at Don Armeni Boat Ramp, the county says.

*The biggest message: Plan ahead, plan ahead, plan ahead. And if you possibly can shift out of commuting during the usual peak hours – via a temporary schedule change, working from home, whatever – please do. And even if the first day doesn’t seem so bad (it won’t, because people really will try something different), don’t just go back to your old ways on day 2 or day 3. They’re continuing to promote 99closure.org as the multi-agency with info you need to plan, now and when the closure’s under way.

We also asked the SDOT rep why, now that the date is set for this, they aren’t considering delaying the Fauntleroy Expressway-related bridge and lane closures until the Viaduct closure is over. SDOT’s rep first said they didn’t think there would be a problem because the bridge closures are at night only. We noted that the surface Spokane St. lane closures UNDER the west end of the bridge include some daytime work and he said he would “take that back” (to HQ) for consideration.

12:54 PM: Video of the briefing/Q&A, unedited, is now added toward the start of this story. As the closure approaches, we’ll continue with previews and updates, and if you have questions, we’ll do our best to get and publish the answers.

Still no date set for the ~2-week Alaskan Way Viaduct closure that’s planned when the Highway 99 tunneling machine goes beneath it. But WSDOT is continuing to make presentations about the preparations. Monday morning, the slide deck you see above will be part of a briefing given to the City Council. Nothing major or new in it, but it includes graphics showing bus rerouting plans as well as extra parking for West Seattle Water Taxi riders. In the slide deck, you’ll again see the promise that advance notice of the closure will be provided; this past Wednesday in West Seattle, WSDOT reps were at the Southwest District Council meeting to talk about closure preps, and they reiterated the intent for two weeks’ warning. If that holds true, it means we’re getting closer to having the closure in May. SWDC members expressed concern that the closure would slide into the summer months, pointing out how busy Harbor Avenue gets on summer nights even without potentially hundreds of commuters returning to their vehicles. Monday’s scheduled briefers are Todd Trepanier and Dave Sowers from WSDOT; SDOT director Scott Kubly; and Victor Obeso from King County Metro. The council briefing meeting starts at 9:30 am Monday, and this is on the agenda for 10:25 am; you can watch live via Seattle Channel, cable 21 or seattlechannel.org.

Nine days after the last Highway 99 tunnel-machine update, WSDOT just published another one – but it still doesn’t answer the big question of when the Alaskan Way Viaduct will close so the machine can tunnel beneath it. The update goes into great detail about how crews are working in “hyperbaric” conditions, and includes this :34 video:

WSDOT has said it hopes to provide two weeks advance notice of the two-weeks-or-so closure, so at this point it would seem unlikely to start before mid-April. The state is continuing to add info to its special closure-info website at 99closure.org.

Today’s update also included a note that results of the March Viaduct inspection are available:

Survey crews measured approximately 5/16 of an inch of settlement near Seneca Street and between 1/8 and 1/4 inch of settlement at the Columbia Street on-ramp. Crews also observed upward movement of up to 1 inch at some locations at the south end of the structure. This upward movement is uniform in nature. No new cracking or structural damage was found.

That’s the entirety of the update published here.

(WSDOT photo from last week – workers walking toward the tunneling machine’s back end)

Another update this afternoon on the Highway 99 tunnel project, currently in a “maintenance stop” getting ready to tunnel beneath the Alaskan Way Viaduct, which WSDOT plans to close for about two weeks when that happens.

No date yet but WSDOT’s update says they’re getting closer:

Inspections and routine maintenance of the SR 99 tunneling machine are ongoing as Seattle Tunnel Partners continues preparing the machine for its drive beneath the Alaskan Way Viaduct.

Crews have been performing planned maintenance since the machine reached a maintenance stop earlier this month. They’ve also been preparing for a series of inspections that must occur in hyperbaric conditions. Hyperbaric conditions are those in which the air pressure is greater than the atmosphere we live and breathe in every day – similar to what scuba divers experience during the course of an underwater dive. This post explains the process for completing hyperbaric work.

So far this week, STP crews have completed a total of 10 hyperbaric shifts in the chamber behind the tunneling machine’s cutterhead. Most of that time has been devoted to cleaning muck from the cutterhead openings and building the platforms crews will stand on as they perform the inspections.

The inspections are expected to take several more days. STP will determine the expected duration of the remaining maintenance based on the results of the inspections.

The end of the maintenance period will usher in the next step in Bertha’s journey: a trip beneath the viaduct. WSDOT plans to close the viaduct for approximately two weeks to allow the machine to pass beneath the structure.

We will provide the public with advance notice of the closure, but the start date isn’t yet known. It will depend on the amount of work that must be completed while the machine is in the maintenance stop. Check 99closure.org for additional details as the closure approaches.

Local transportation and transit agencies have not yet formally announced their plans for what’ll change to help mobility during the Viaduct closure, but some tentative plans were previewed at last month’s West Seattle Transportation Coalition meeting – here’s our coverage.

P.S. WSDOT’s 99closure.org site also is adding more detailed information you might not have seen, including this, and an FAQ.

Another Highway 99 tunnel update from WSDOT this afternoon. This time, the state has told its contractor, according to the update, “that they could continue mining to a planned maintenance stop near Yesler Way. The notification came as STP completed the 25-ring demonstration period that was put in place when mining resumed on Feb. 23. The underground maintenance stop is approximately 120 feet north of the tunneling machine’s current location near South Washington Street. The machine has traveled a total of 1,437 feet and the bored section of the SR 99 tunnel is now 15 percent complete.” That maintenance stop is where, WSDOT says, the machine could undergo “several weeks” of work before it gets ready to tunnel beneath the Alaskan Way Viaduct, which will be closed for about two weeks as a precaution while the machine is beneath it.

In case you missed our coverage, WSDOT reps briefed the West Seattle Transportation Coalition on the closure plan last month; they expect to set a closure date with about two weeks’ warning.

By Tracy Record
West Seattle Blog editor

Now that the Highway 99 tunneling machine is back at work, planning is back in high gear for closing the Alaskan Way Viaduct for about two weeks while the digging happens beneath it.

The West Seattle Transportation Coalition got a preview of the plan – including Metro bus reroutes – last night.

The preview included details such as how close the tunneling machine will be to the underside of The Viaduct’s columns (within 14 feet at one point). If it continues operating as planned from hereon out, the closure is likely to start sometime in March, and WSDOT hopes to set a date with about two weeks notice.

“We do understand it’s going to have regional impacts and businesses and travelers are going to need notice,” said Chris Brown of WSDOT, one of the two main briefers along with, providing Metro details, Chris Arkills, the West Seattleite who is County Executive Dow Constantine‘s transportation adviser.

Everything they said – and everything WSTC members/attendees asked – is all in our video atop this story, one hour and 15 minutes worth. You can listen instead of watching, as there are no visuals – no projector. Brown began with some backstory on the project – we’ve reported on that so often, we’re not recapping it here, but he explored a few points that we do mention after the closure-related info – keep reading!

First:

Read More

ORIGINAL REPORT, 12:47 PM TUESDAY: Just in from WSDOT – it’s “conditionally lifted” the suspension order for its Highway 99 tunnel contractor, and the tunneling machine is digging again. Here’s the announcement:

Seattle Tunnel Partners has received conditional permission to resume tunneling operations on the SR 99 Tunnel Project. STP resumed mining today after WSDOT conditionally lifted the “suspension for cause” that halted mining and barging-related activities last month following two safety incidents.

As part of the conditions for lifting the suspension for cause, STP will be permitted to tunnel forward and install approximately 25 concrete tunnel rings. During this time, they must demonstrate that they have implemented a number of changes to ensure they can safely continue mining. These changes include:

Updated tunnel work and quality plans, including calculations of the amount of soil removed during excavation of each tunnel ring.
Realignment of key personnel within their quality assurance program.
New quality assurance protocols.
New personnel at key positions within the tunneling operation.
Restructured daily tunneling meetings that include additional participants and protocols.

WSDOT made the decision to conditionally lift the suspension for cause after its team of tunneling experts evaluated documentation submitted by STP over the past several weeks. While mining can resume, barging activities are still restricted pending submittal of additional documentation.

Read More

(WSDOT image)

After three weeks of tunnel-machine stopdown, still no restart plan, but WSDOT is just out with another project update, saying that work is about to start to fix pier damage done in the process of barging what was being dug out. Also: No new sinking – instead, some “upward movement”:

Seattle Tunnel Partners is set to repair damage that occurred at Terminal 46 during the Jan. 12 barging incident. STP will remove 22 damaged timber piles from the pier at the northern edge of Terminal 46 and replace them with temporary piles. Work is expected to begin in the coming days and could take up to 10 days to complete, according to STP.

WSDOT and STP continue to work together to address the “suspension for cause” that halted tunneling and barging operations on Jan. 14. STP crews are prepared to remove excavated soil by truck if tunneling resumes before the pier at Terminal 46 is repaired.

You can watch the pier repairs unfold on our construction camera. The labels on the image (above) call out some of the key elements you’ll see in the regularly updated time-lapse images.

Ground monitoring update

It’s been approximately two weeks since Seattle Tunnel Partners turned off the deep dewatering wells that were used to control groundwater near the access pit. There was some upward ground movement in the days following the shut-off, but the movement quickly stabilized. The degree of movement tapers off over several city blocks and is uniform in nature, which poses little to no risk of damage to the Alaskan Way Viaduct or buildings.

Some ground survey points in the vicinity of the pit show as much as 3/5 inch of upward movement since Jan. 22 when STP began turning off the wells. Some of the Alaskan Way Viaduct columns and buildings show similar movement.

STP had additional, shallower dewatering wells in operation during the tunneling machine repair effort. They turned off the final two shallow wells on Thursday evening. STP and WSDOT continue to monitor the ground, buildings, utilities and the viaduct.

When the digging stopped last month, WSDOT says, 1,280 feet of tunneling was complete, of the expected 9,270 feet.

Two weeks after WSDOT told its Highway 99 tunnel contractor to stop digging, it’s still not ready to give the green light for digging to resume, according to this update late today:

Last week, Seattle Tunnel Partners submitted their analysis of recent incidents on the SR 99 Tunnel Project. WSDOT and their tunnel experts determined STP’s analysis did not sufficiently address the cause of these incidents or specify how they would prevent them from occurring in the future.

(WSDOT graphic from January 13th)
WSDOT has notified the contractor that in order to lift the suspension for cause, STP must confirm that:

· The tunneling machine is operating as intended and meets the design-build contract’s technical requirements.

· All necessary training for staff on the tunneling machine is complete.

· The tunneling work plan is updated to address the issues that led to the sinkhole.

· Processes are in place to ensure STP’s tunneling work plan is followed.

· STP updates its quality program to ensure key quality program managers are involved in all tunneling activities.

It is STP’s responsibility to determine how to address these issues and ensure they are in compliance with the technical requirements of the contract. This section of the tunnel drive was designed to be a test section for operation of the tunneling machine. With approximately 250 feet of tunneling prior to reaching the next planned maintenance stop, demonstration of these steps is critical.

No indication of exactly how this is affecting the schedule aside from obviously pushing it back at least two weeks – including the expected Viaduct closure when the tunnel machine goes beneath it, previously expected to happen in March.

Just in, an update from WSDOT, following up on its order last week telling its contractor to stop Highway 99 tunneling because of recent incidents including a sinkhole and trouble with the barge that was receiving excavated material:

Last week, WSDOT notified Seattle Tunnel Partners that they must “suspend for cause” tunneling operations involving the tunneling machine and the loading of barges. WSDOT took this step to ensure STP’s work can proceed safely following recent incidents on the SR 99 Tunnel Project. Safety remains the top priority for the project and we can’t speculate on when tunneling will resume.

In response to the suspension for cause, STP has informed WSDOT they are analyzing the recent incidents and intend to provide follow-up information this week. WSDOT, in consultation with its tunneling experts, will then review the information and determine the appropriate next steps.

STP has notified WSDOT they plan to sequentially turn off the deep dewatering wells soon. These wells, which have been used to control groundwater, were previously scheduled to be shut off when the tunneling machine reaches the next planned maintenance stop. With tunneling operations currently on hold, STP has determined that there is an opportunity to turn off the wells earlier than planned. We will continue to monitor movement of the ground, structures, utilities and the viaduct. Additional information about our ground monitoring program can be found here.

ORIGINAL REPORT, 12:13 PM: Just in from WSDOT:

The Alaskan Way Viaduct Replacement Program (WSDOT) is in the process of notifying Seattle Tunnel Partners to suspend tunneling operations involving the tunnel boring machine, a “Suspension for Cause” in contractual terms, until such time as WSDOT lifts the suspension in writing. We will provide a copy of the letter after it is delivered to STP.

The following is a statement from Secretary of Transportation Lynn Peterson:

“In light of recent incidents on the SR 99 Tunnel Project, WSDOT is notifying the contractor that they must suspend tunneling work for cause. I share the Governor’s concern for public safety and we want to ensure that the contractor has the right protocols in place to proceed with their work safely.

We are asking that the contractor complete root cause analysis and take the appropriate steps to ensure that incidents, such as the sinkhole near the repair pit, do not occur again. STP will not be allowed to resume tunneling until their analysis and work plans meet the satisfaction of our experts.

I want to remind everyone that replacing the viaduct is critical to public safety. We have conducted surveys of the viaduct and no movement has been observed; surveys will continue. The tunneling work must proceed, but it must proceed safely.”

This week alone, besides the 35′ x 20′ x 15′ sinkhole, there also was trouble with the barge being used for excavation spoils. WSDOT stresses, however, that other work – such as the Highway 99 lane closures starting next week for tunnel-related sign installation – goes on. More as we get it. Per WSDOT’s “Follow Bertha” page, as of Tuesday, 1,280 feet of tunneling had been completed, of 9,270 feet in all.

P.S. Checking our archives – available via Google cache until our full site is up – we note that yesterday was the seventh anniversary of the announcement by then-Gov. Gregoire, then-Mayor Nickels, and then-County Executive Sims that a deep-bore tunnel had been chosen to replace the Alaskan Way Viaduct.

4:02 PM UPDATE: As promised, WSDOT has made public the letter sent to Seattle Tunnel Partners. You can read it in its entirety here. Here’s what’s at the heart of it:

WSDOT has determined that STP has failed to correct conditions unsafe for the Project personnel or general public, and failed to comply with Governmental Approvals, Law, or otherwise carry out the requirements of the Contract Documents. Therefore, WSDOT has the authority to suspend work for cause, pursuant to Contract Sections 14.2 (a) and 14.2(b) and Technical Requirements Section 2.52.7.3.5.

On the night of January 12, 2016, a sinkhole was detected over the tunnel. The full extent of ground loss is not yet determined and settlement is increasing. STP has yet to provide a detailed analysis of the cause of the observed ground settlement, or a plan for modifying tunneling operations to ensure positive ground control at all stages of tunneling (TR 2.32), and to prevent settlement outside of tolerance in the future (see TR 2.52).

On Tuesday January 12, 201 6, STP’s barge filling operation resulted in a barge listing beyond STP’s control. As a result the barge was either let go or broke free from the pier, spilling tunnel spoils into Elliott Bay, and drifted out of control damaging both Terminal 46 and Pier 48. These events created an unpermitted spill of material and posed a hazard to project personnel and the public.

WSDOT requests a meeting with STP within 24 hours to address this matter.

4:10 PM: More news today from WSDOT, the day after the Highway 99 tunneling machine had to stop while they sorted out a problem with the barge that was collecting excavation spoils. The barge problem isn’t fixed yet, but they brought in some trucks, and digging resumed. Then came a sinkhole. Here’s the WSDOT update sent this afternoon:

Seattle Tunnel Partners resumed mining Tuesday evening, using trucks to remove excavated material while they continued working to resolve an issue with a soil-removal barge. STP crews resumed excavation at 7 p.m. Tuesday.

(WSDOT graphic)
Approximately two hours later, a sinkhole developed within STP’s work zone near South Main Street, about 35 feet north of the access pit. It is located more than 100 feet south of the cutterhead’s current location, in ground that crews mined through last week. STP filled the sinkhole overnight with 250 cubic yards of concrete.

This section of the tunnel drive is protected by an underground wall built by STP before tunneling. The wall was designed to isolate ground movement and protect the nearby Alaskan Way Viaduct. A manual survey of the viaduct conducted after the sinkhole developed found no movement. WSDOT and STP will continue surveying and monitoring the ground, viaduct, utilities and other structures.

The cause of the sinkhole is still under investigation. STP is analyzing the portion of the tunnel that crews have excavated since mining resumed. There is no indication that any other locations have experienced ground loss.

STP is reviewing their daily operations as a result of this incident. Immediately they will enhance monitoring protocols by requiring crews to manually verify the amount of soil removed during excavation of each ring.

The protocols STP outlined to enhance monitoring were used in the first 1,000 feet of tunneling and WSDOT is disappointed they were not used when STP restarted tunneling in December 2015. STP has several hundred feet of mining before they reach the next planned maintenance stop. Before leaving the maintenance stop, STP’s operational protocols will undergo an additional review by an expert to assure public safety.

STP has temporarily stopped mining to prepare the muck storage pit to receive excavated material. They plan to resume tunneling this week using trucks to remove excavated material. …

Safety remains our top priority as we work to replace the seismically vulnerable Alaskan Way Viaduct. We expect STP to further investigate this incident and take the appropriate corrective action as they continue to build this important project.

ADDED 6:31 PM: We asked WSDOT’s project spokesperson Laura Newborn about the sinkhole’s size: “According to Chris Dixon, the dimensions of the sinkhole were 35 feet long, 20 feet wide and 15 feet deep.”