We've received a number of questions about the ground settlement measured recently near the SR 99 tunnel access pit. Answers to some of these questions can be found below. We'll continue to update this post as new questions come in.
Updated Jan. 21
What kind of settlement has WSDOT seen near the access pit and in Pioneer Square?
In late November, Seattle Tunnel Partners surveyors detected a little over an inch of ground settlement near the pit crews are building to access and repair the SR 99 tunneling machine. We have also seen similar settlement on the Alaskan Way Viaduct; the amount of settlement lessens in the surrounding area. Settlement levels in the area have remained stable since Nov. 24, but we continue to closely monitor the area. The investigation into the source of this settlement is continuing.
Have buildings been damaged in Pioneer Square?
We have worked with property owners and managers to complete approximately 50 visual assessments of buildings in areas of greater ground settlement. During these assessments, an architect with expertise in historic buildings checked portions of each building to look for signs of recent damage that might require immediate attention. So far, a small amount of recent cosmetic cracking has been noted in some buildings. Most buildings have shown no signs of recent settlement.
How would settlement affect a building?
You may notice new cracks or changes to existing cracks. You may also notice doors or windows that are sticking or do not open properly. If the building settles more than the ground outside, utility services also could be affected. If you notice such changes in your building, please keep a list or take photos, and follow the contact information below.
What should I do if I see new damage in my building?
If you are a resident or tenant, please contact your property manager or building owner. Building owners should contact the Alaskan Way Viaduct Replacement Program (1-888-AWV-LINE or firstname.lastname@example.org) to report any settlement-related concerns. A WSDOT representative will contact you to arrange for a mutually convenient time to inspect your building. If you have photos, please share them with our staff.
How do I file a claim if I have building damage?
If you feel your building has been damaged as a result of ground settlement caused by the project, you can contact us at 1-888-AWV-LINE or email@example.com
What is WSDOT doing to monitor buildings?
We implemented a comprehensive program to monitor ground movement during SR 99 tunnel construction. Crews are currently analyzing data from this system and conducting extensive surveys near the work zone.
For buildings closest to the tunnel route, crews previously conducted pre-construction surveys that incorporated photo and video to document each building’s interior and exterior condition. We will be conducting similar building condition surveys for additional buildings within Pioneer Square. These survey results will serve as a resource for both property owners and the project team by documenting the current condition of each building.
Can WSDOT expand the monitoring program to include more buildings?
Our monitoring system was designed to measure ground movement during tunneling. As part of that system, monitors were installed both in the ground and on structures. The most significant recent settlement has occurred in areas that already include both ground and building monitors. However, some settlement has been observed in areas that are not actively monitored. As a result, we do not have specific settlement data for some of these buildings.
Structural engineers and surveyors are inspecting buildings and infrastructure in all areas where settlement was detected. Decisions about expanding the scope of the monitoring program will be made after that analysis is completed.
Does WSDOT have a plan if settlement continues?
WSDOT and Seattle Tunnel Partners conducted additional survey work early Sunday morning to further assess the amount and extent of settlement that recently occurred on and near the Alaskan Way Viaduct.
Some of the data was inconclusive and analysis is still underway; however, WSDOT observed that a small amount of differential settlement is occurring near the access pit. Differential settlement is when the ground settles unevenly over an area. When the ground settles evenly or uniformly over an area, there is less risk of damage.
The additional survey work did not find that the differential settlement has caused any new damage to the viaduct nor have we observed any damage to buildings or utilities in the surrounding area. On-the-ground surveys will continue this week by historic architects and structural engineers.
Public safety is our top priority and while we have not seen any damage, Seattle Tunnel Partners is taking the prudent step to stop dewatering. The contractor will work with its geostructural designer to stop the dewatering in a deliberate manner in order to ensure worker safety and the structural integrity of the access pit and surrounding structures.
Data analysis, collection and monitoring will continue and we will provide updates as we have new information to share.
The SR 99 Battery Street Tunnel will be closed to traffic from 9 p.m. Saturday, Nov. 8 to 8 a.m. Sunday, Nov. 9. The closure will allow Seattle Department of Transportation crews to do routine maintenance work. Drivers will follow signed detours to get around the closure.
WSDOT archaeologists continue to work with the Federal Highway Administration, tribal governments and the Washington State Department of Archaeology and Historic Preservation to develop an investigative plan to determine whether the shell deposit observed in the access pit last week is of cultural significance.
Consistent with the National Historic Preservation Act and in preparation for the investigation moving forward later this week, we have temporarily disabled our access pit construction cameras. WSDOT treats potential cultural resources with respect, therefore the investigation will not be documented through our construction cameras. All non-access pit cameras are still available. We will repost the access pit cameras at the appropriate time.
On Oct. 23, WSDOT archaeologists monitoring the access pit excavation observed a deposit containing shell material that requires further evaluation and may indicate the presence of cultural materials. No artifacts or human remains were found. WSDOT has very strict protocols when archeological material is discovered and those protocols were followed today. Excavation activities in the access pit have stopped and we are now coordinating with the Federal Highway Administration and tribal governments, and the Washington State Department of Archeology and Historic Preservation to determine the next steps. As more information is available to share with the public, we will pass it along.
Seattle Tunnel Partners continues to prepare for excavation of the circular pit (pdf 2.5 Mb) crews will use to access and repair Bertha, the SR 99 tunneling machine. Crews are installing wells to lower groundwater in enclosed areas near the machine. This will make it easier to excavate the access pit and move the tunneling machine into the pit later this fall.
Early warning: Four-day closure of SR 99 coming in late August
In late August, crews building the future north portal of the SR 99 tunnel will close SR 99/Aurora Avenue North near South Lake Union for four days. During this closure, crews will demolish and replace the section of SR 99 that crosses above Broad Street.
To minimize the need for additional closures, separate crews will complete the following work elsewhere along the SR 99 corridor during this time:
Drivers should plan ahead for SR 99 closures from Friday night, Aug. 22 to Wednesday morning, Aug. 27. View a map of the closure.
Travelers who use SR 99 should consider the following:
Know before you go and have a backup plan
Those who must drive are encouraged to stay engaged and check traffic conditions frequently via WSDOT’s web, mobile and phone-based traveler information systems.
As we head into the last long weekend of the summer, we thought it was time for an update on Seattle Tunnel Partners’ progress to build the circular pit (pdf 2.5 Mb) that crews will use to access and repair the SR 99 tunneling machine.
The last time we updated you, STP announced that crews would continue to install the underground walls of the access pit through August. STP has notified WSDOT that there is one pile left to install before the circular pit is completed; they expect to finish it by the end of the week. Additional piles will be installed near the pit as part of the support system for the modular lift tower - the large crane that will hoist the machine’s 2,000-ton cutterhead and drive unit out of the ground.
Next up, dewatering wells. STP has notified us that crews will install several dewatering wells both inside the access pit and inside the enclosed area south of the access pit around the tunneling machine. Prep work is beginning now and crews should have them installed by mid-September. These wells will lower the groundwater inside the enclosed areas to make it easier to move the tunneling machine into the access pit, as well as to excavate the pit.
STP has notified us that tunneling machine operators will start Bertha in order to check internal systems in preparation for mining into the circular pit. Also, pieces of the three cranes that will be used to lift tunneling machine pieces out of the access pit are continuing to arrive from around the world. Soon you will see these pieces being assembled next to the access pit.
We made it, Seattle commuters. It wasn’t easy, but the longest closure of SR 99 in nearly three years has come to an end.
Both directions of the highway reopened to traffic at 4 a.m. Wednesday, Aug. 27.
Thanks for doing your part to reduce congestion. Traffic was worse than usual, but we expected that. And had you not heeded our suggestions, things would have been much, much worse.
Of course when you’re sitting in traffic, it’s easy to forget that the headaches we’re enduring have tangible benefits. In the case of the four-day SR 99 closure, we came away with plenty to show for our shared sacrifice.
Most notably, crews building the future north portal of the SR 99 tunnel demolished and replaced the section of SR 99 that crosses above Broad Street in Seattle. It looks easy in this time-lapse video, but completing this work and reopening the highway in four days was no small feat.
Additionally, during the weekend portion of the closure, crews took advantage of the empty highway by completing necessary work elsewhere along the corridor. They replaced 81 concrete panels on SR 99 south of downtown, repaired an expansion joint at the Seneca Street off-ramp from northbound SR 99 and cleared ivy from the Alaskan Way Viaduct to make future maintenance of the structure easier.
Know before you go
To minimize the need for additional closures, several projects are taking advantage of the SR 99 closure to complete work.
Broad Street bridge demolition: The bridge over Broad Street is now completely gone. Crews have been busy compacting fill material that will provide the foundation for the new SR 99 roadway.
Utility work at Harrison Street: Crews continue to make progress on the new sewer line under SR 99 at Harrison Street. Work is also underway to underground several electric lines.
When State Route 99 closes for four straight days starting Friday night, Aug. 22, you can expect more congestion and delays on surface streets getting into and out of downtown Seattle. We’re expecting more bikes on the road as travelers try alternate ways to reach their destination.
To keep everyone moving safely, drivers and bicyclists will need to be especially mindful of each other as they use crowded streets and intersections. Obeying the law is essential. In Washington state, bicycles are legally considered vehicles on the road. For cyclists, this means following the same rules of the road as drivers. For drivers, this means using best practices and treating cyclists as equals who have the same rights to the road as you.
Here are a few common sense tips to help all commuters get along:
Finally, both drivers and bicyclists should keep an eye out for pedestrians and remember that pedestrians have the right of way at crosswalks.
Today, Seattle Tunnel Partners notified us that building the underground walls of the circular pit (pdf 2.5 Mb) crews will use to access and repair the SR 99 tunneling machine will continue through August. While this date is later than anticipated, STP reports that tunneling is still expected to resume as scheduled in March 2015.
Building a self-supporting, concrete ring that is 120 feet deep and 80 feet wide is no easy task, especially given the difficult ground conditions near South Jackson Street. STP crews have completed more than half of the underground piles and are working around-the-clock, seven days a week to complete the approximately 31 remaining piles.
There are several reasons the work is taking longer than anticipated. One factor is the addition of 11 piles to the design, bringing the total number of piles to approximately 84. Crews are also working with exceptionally large interlocking piles, which are necessary to make the pit self-supporting without tiebacks or other reinforcements. A self-supporting pit is what will allow the tunneling machine to mine through its walls, but the large piles take longer to install than standard piles.
While pile work continues, crews are making progress on other areas of the repair plan on schedule, including:
The Seafair Torchlight Run will close all lanes of northbound SR 99 between South Spokane Street and the north end of the Battery Street Tunnel from 5:30 p.m. to 7:45 p.m. Saturday, July 26. Additionally, the southbound SR 99 off-ramp to Western Avenue will be closed from 6 p.m. to 8 p.m. Saturday.
How to replace a bridge in four days
In August, crews working on the North Access contract near the SR 99 tunnel’s north portal will replace the bridge on SR 99 over Broad Street. Not sure what bridge we’re talking about? Don’t worry. Even the most seasoned SR 99 commuter may not realize they are crossing a bridge at Broad Street.
That bridge, and Broad Street itself, must be completely transformed to make room for the future connection to the tunnel’s north portal and on- and off-ramps at Harrison and Republican streets.
Crews have already begun to fill in Broad Street with recycled concrete from the former roadway. Once we close this section of SR 99 to traffic, crews will bring in heavy equipment and demolish the old bridge in about 12 hours. They’ll then spend the next two days adding more fill material to make the new roadway level with the existing lanes of SR 99. After paving the new SR 99 roadway, crews will stripe the lanes and reinstall barriers. Once all of this is completed, SR 99 will reopen.
Demolishing a bridge and building a new road in its place isn’t easy work. It is especially challenging on a major highway through Seattle. To minimize disruptions to drivers, crews will replace this portion of SR 99 in a mere four days. Drivers should plan ahead for SR 99 closures from Friday night, Aug. 22 to Wednesday morning, Aug. 27. Closure details can be found here.
There’s a lot of other WSDOT work that will happen on SR 99 during this closure as well, including utility work at Harrison Street, concrete panel replacement in SODO, expansion joint repairs on the viaduct near the Seneca Street off-ramp and removal of ivy from the viaduct in downtown Seattle.
We will continue to share information to help drivers plan ahead and get around during the closure.
**UPDATE** As of 6 p.m. Sunday, northbound SR 99 is fully open. The Denny Way on-ramp remains closed.
**UPDATE** As of 3 p.m. Sunday, northbound SR 99 is open from South Atlantic Street to the Western Avenue off-ramp. Northbound SR 99 remains closed from the south end of the Battery Street Tunnel to Valley Street.
Construction at the future north and south portals of the SR 99 tunnel will turn northbound SR 99 through Seattle into a no-go zone this weekend. All lanes of northbound SR 99 will be closed through downtown Seattle from 10 p.m. Friday, June 20 to 5 a.m. Monday, June 23.
There’s a lot happening on the roads around Seattle this weekend, and we could use your help to keep traffic moving. Before heading out, drivers should plan their trip by using WSDOT’s traffic tools.
Bertha has always been big. The focus now is on rebuilding Bertha and making her better, according to a new repair work plan unveiled Monday, June 16, by Seattle Tunnel Partners, our design-build contractor for the SR 99 Tunnel Project.
Other major enhancements of the work plan include:
STP will provide WSDOT with additional supporting information about rebuilding the machine in the coming months, in accordance with the design-build contract, to demonstrate how the repairs will meet the contract’s performance and technical requirements, including:
Bertha is currently stopped approximately 60 feet underground between South Jackson and South Main streets. As owner of the machine, STP is responsible for ensuring it functions properly at all times. STP is currently building the underground walls of a circular pit (pdf 2.5 Mb) crews will use to access and repair the machine.
Seattle drivers should prepare for big changes in the Uptown neighborhood and the area around Seattle Center. Beginning the evening of June 1, the Seattle Department of Transportation's Mercer Corridor Project will permanently close Broad Street between Ninth Avenue North and Fifth Avenue North. At the same time, Mercer Street will open to two-way traffic between I-5 and Elliott Avenue West. Roy Street (between Queen Anne Avenue North and Fifth Avenue North) and Queen Anne Avenue (between Roy and Mercer streets) will also convert to two-way operation during this time.
Travelers are advised to use alternate routes and expect lengthy delays because of the Broad Street closure and as drivers adjust to two-way operations on Mercer Street. SDOT will closely monitor the corridor during this transition period and will make adjustments to signal timing as needed. Police officers will also be stationed at key intersections to help traffic flow.
The permanent closure of Broad Street provides space for SDOT crews to widen Mercer Street to its final configuration of three lanes in each direction. The Alaskan Way Viaduct Replacement Program’s North Access team will also be working in the former Broad Street area to build connections between the future SR 99 tunnel and adjacent streets.
Seattle Tunnel Partners crews will close all lanes of southbound State Route 99 during the first full weekend in June to shift traffic to a new southbound routing (pdf 769 Kb) of the highway near Seattle’s stadiums.
Crews will complete a similar shift of the northbound lanes during the June 20-23 weekend. The shifts will make room for STP to continue construction of lanes and ramps that will connect to the SR 99 tunnel. A fuller description of this work is available here.
Traffic will stay in the new configuration until the tunnel opens to traffic. Drivers should expect initial congestion and delays after each traffic shift as travelers adjust to the new routings. Drivers can help keep traffic moving by keeping an eye on the road and other drivers.
Traffic signals at three intersections on Alaskan Way – South Main Street, Yesler Way and Columbia Street – have been shut off due to utility relocation associated with the SR 99 Tunnel Project. The signal outages are an extension of a planned a temporary power outage that occurred over the weekend.
Seattle Police officers will direct traffic at Yesler Way and Columbia Street until 7 p.m. Monday, May 19; South Main Street is functioning as an all-way stop. The intersections will function as all-way stops from 7 p.m. until power is restored at 4 a.m. Tuesday, May 20. Additional signals may be shut off overnight as crews continue their work, and by law should be treated as all-way stops.
As part of the SR 99 Tunnel Project, utility relocation being performed by Seattle City Light crews will require a temporary power outage this weekend. Starting at 3 a.m. on Sunday, May 18, and ending by 6 a.m. on Monday, May 19, police officers will direct traffic at four intersections on Alaskan Way. The intersections that will be impacted are South Main Street, South Washington Street, Yesler Way and Columbia Street.
Drivers should plan for possible congestion on southbound State Route 99 near the stadiums on Saturday.
The southbound SR 99 off-ramp to South Atlantic Street will be closed between 7 a.m. and 5 p.m. on Saturday, May 17. The right lane of southbound 99 will also be closed during this time between South King and South Atlantic streets. The lane and the exit will reopen at least two hours before the 7 p.m. Sounders game at CenturyLink Field.
During the closure, Seattle Tunnel Partners’ crews will continue preparing to reroute the temporary section of SR 99 that bypasses the tunnel construction zone near the stadiums. Crews are rerouting this section of SR 99 to make room for construction of permanent lanes and ramps into and out of the new SR 99 tunnel.
Environmental review of Seattle Tunnel Partners’ plan for accessing and repairing the SR 99 tunneling machine is now complete. The on-schedule completion of the review clears the way for STP to build the 120-foot-deep pit that will allow crews to access the machine, which is located about 60 feet below the surface in a fenced-off construction zone between South Jackson and South Main streets.
The ground above the machine has been closed for construction since 2012, but further environmental review was required for this additional work.
Watch construction unfold online
Pit construction will be hard to see in person because crews recently built a wall to shield neighbors from construction noise. The best spot to view STP’s work is online at our newly installed time-lapse camera.
The camera went live on Saturday, May 3. On May 7, following completion of the environmental review, STP began assembling equipment where the pit will soon take shape. This work is consistent with the schedule STP released last month. Crews are relocating utilities and will spend the next week injecting grout into the ground above the machine. Later this month, they’ll begin installing the pit’s underground walls.
STP’s schedule shows that excavation of the pit will last from late July through September. When the pit is complete, the machine will tunnel into it. Crews will then partially disassemble the machine and make repairs. These conceptual drawings illustrate the basic idea.
In the week since Seattle Tunnel Partners, the SR 99 tunnel contractor, announced their new constructions schedule, we’ve been asked about who will be responsible for paying for the costs associated with the delay.
WSDOT’s answer: Seattle Tunnel Partners has requested $125 million in compensation. WSDOT has denied their request.
Understanding change orders
The formal mechanism we use to make changes to our construction contracts is known as a change order. Requests for change orders can be submitted to us by a contractor or we can initiate them ourselves.
There are many reasons for issuing change orders. Some examples include:
As of April 1, there are outstanding change order requests from STP to WSDOT on the SR 99 tunnel contract totaling $188 million. Of that $188 million, we have denied $157 million, over 80 percent. The remaining $31 million in requests is under review.
STP’s largest request to date is for $125 million in additional compensation and time because they believe the tunneling machine was damaged by a steel well casing originally installed by WSDOT.
Our position on this issue is clear: WSDOT informed STP and other prospective bidders of the well casing in documents contained within the request for proposals that was issued for the project in 2010. It is the contractor’s responsibility to ensure that their design and construction activities take into account all of the information provided to them. Therefore, we denied their request.
The path forward
The process for resolving disputes within the tunnel contract is prescriptive. It requires multiple steps by both parties. Should STP continue to pursue entitlement related to the well casing, it will take time to resolve. Nonetheless, we believe WSDOT and the state will prevail.
The outcome of this process is important to everyone involved, and we recognize that there will be great public interest in this matter moving forward. We will continue to provide updates while respecting the contractor’s rights and the process specified in the contract. We will also continue to focus on the job at hand -- resuming tunneling and opening the tunnel to traffic as safely and quickly as possible.
SEATTLE – Drivers should get ready for a spring and summer of increasing construction near the intersection of Dexter Avenue North and Harrison Street. Next week, crews working for the Washington State Department of Transportation will begin relocating utilities along Dexter and Harrison as they prepare to build new on- and off-ramps to the State Route 99 tunnel. Work will shift one block north to Republican Street this summer.
Travelers in the area should be prepared for additional congestion and changing conditions beginning the week of April 28 and lasting through summer. Here’s what you can expect.
Bicyclists and transit
In addition to the closures listed above, there will be nighttime and weekend closures of Dexter Avenue North between Republican and Thomas streets. Drivers and bicyclists will be detoured to Eighth Avenue North. The schedule through May 6 is listed below. Be sure to check our traffic page for updates beyond May 6.
See map for current and future work zone.
Today, Seattle Tunnel Partners, our design-build contractor for the tunnel project, released a new schedule that shows the SR 99 tunneling machine will resume digging by the end of March 2015.
Construction will begin late next month on the pit STP will use to access and repair damage to the machine, which stopped tunneling in December. Building the pit (pdf 715 kb) is the first of several steps STP has laid out to resume tunneling:
These construction activities will be addressed in accordance with the SR 99 tunnel contract. The updated construction timeline delays tunnel boring by up to 16 months, but STP hopes to recover as much as five months of schedule to meet the November 2016 tunnel opening date we established in our 2010 request for proposals. STP had proposed opening the tunnel in late 2015, 11 months earlier than our original requirement.
STP has informed us that crews will replace the machine’s main bearing and install a more robust seal system, which could include strengthening the seals, installing redundant systems, and adding monitoring equipment. Additional details will be included in a plan to be submitted to us for review by June 16.
The repair schedule will include additional time to accommodate potential improvements to the machine that STP or the machine’s manufacturer, Hitachi Zosen Corp., might choose to make after the cutterhead is removed and crews are able to perform a full inspection. We will work with our strategic technical advisory team, made up of international and national tunneling experts, as well as consultants, to review the plan.
More than $750 million in continuing work
We’re disappointed by this delay, but believe the schedule is moving in the right direction. We’re also focused on the bigger picture, which includes more than $750 million worth of work at the tunnel portals and elsewhere along the SR 99 corridor. That construction is not affected by the tunneling stoppage and continues full speed ahead.
West of Seattle’s stadiums, crews are building the future connection between the tunnel and the new section of SR 99 that was completed in 2012 after the viaduct’s southern mile was demolished. Crews are also making progress on the south portal operations building, which will house lighting, ventilation, emergency systems and other vital components needed to operate the tunnel.
Meanwhile, at the tunnel’s future north portal, crews are building the connection between the tunnel and Aurora Avenue North, the north portal operations building and the 80-foot-deep pit where the tunneling machine will emerge at the end of its journey beneath downtown.
Work is also ongoing in Frederickson, Wash., where crews have manufactured 72 percent of the concrete segments that are pieced together to form the tunnel’s exterior walls.
We do our best to tell you about the progress we’re making as we work to replace the Alaskan Way Viaduct. But the best way to appreciate it is to see it in photographs.
For example, it wasn’t too long ago that the viaduct was nearly twice as long as it is today. Then, in 2011, crews demolished the southern mile of the double-deck highway, replacing it with a new side-by-side section of SR 99 near the stadiums. Also new to the neighborhood is the South Atlantic Street overpass, which opened earlier this year. The new overpass dramatically shortens trips between the freeways and the Port of Seattle’s busiest freight terminal by allowing trucks and other traffic to bypass train blockages on South Atlantic Street. These images show the transformation.
To help you see more of the progress we’re making, we’ve launched a new photo set on Flickr. The tunneling machine may not be moving forward at the moment, but other work is. And it’s a striking story in photos. Let us show you.
The on-ramp from Denny Way to northbound State Route 99/Aurora Avenue North will close on Monday, April 21, and Tuesday, April 22, from 11:30 p.m. to 5 a.m. Also during those hours, the right northbound lane of Aurora Avenue North will be closed between the Battery Street Tunnel and Valley Street.
The closures will allow workers to improve street lighting along Aurora Avenue North. The work is part of the SR 99 tunnel’s north access project, which is building the connections between city streets and the future north portal of the SR 99 tunnel.
Drivers on SR 99 in Seattle will soon see a noise-blocking wall rise out of the ground near the spot where crews will dig a pit to reach and repair Bertha, the SR 99 tunneling machine. The double-plywood wall, which will be as tall as the lower deck of the Alaskan Way Viaduct, is designed to shield neighbors from construction noise associated with the repairs. It will stretch along the west side of the viaduct between South Jackson and South Main streets. Construction of the wall should take about two weeks.
Our contractor for the tunnel project, Seattle Tunnel Partners (STP), is still finalizing their repair plan for the machine. What we know so far is that crews will dig a 120-foot-deep pit in front of the machine, which is located about 60 feet below the surface between Jackson and Main. The machine will then tunnel forward into the pit so crews can partially disassemble it and make repairs to the seal system and main bearing. These conceptual drawings illustrate the basic idea.
Because this is a design-build contract, STP is responsible for developing and implementing the plan to fix the machine and resume tunneling. Schedule and budget impacts of the tunneling stoppage, which began in December 2013, won’t be known until after the plan has been finalized. The contract currently requires STP to open the tunnel to drivers by Jan. 2, 2016.
You’ve been hearing a lot lately about our efforts to replace the State Route 99 Alaskan Way Viaduct. This is a big, complex undertaking. And as we all know, we’ve encountered some challenges. Join us this Thursday at 6 p.m. at Milepost 31 as speakers from WSDOT and our tunnel contractor, Seattle Tunnel Partners (STP), explain what's being done to address these challenges and get Bertha, the SR 99 tunneling machine, moving again.
The State Route 99 Alaskan Way Viaduct will be closed for additional inspection work Saturday, March 22.
Bridge inspectors will close all lanes of the viaduct between South Spokane Street and the Battery Street Tunnel from 4:30 a.m. to 7 p.m. Saturday. During the closure, crews will install monitoring devices on the viaduct to track the movement and growth of cracks over time. Engineers will use this data to help identify potential repairs.
Although vulnerable to earthquakes, the viaduct remains safe for everyday use. It will continue to provide a vital link to and through downtown Seattle until the SR 99 tunnel opens to traffic.
Be prepared for other closures this weekend
In addition to Saturday's viaduct inspection closure, the Seattle Department of Transportation (SDOT) will have a nighttime closure on southbound SR 99 as well as daytime closures of the Mercer Street ramps to I-5 as part of the Mercer Corridor Project. SDOT crews will close all southbound lanes of SR 99 between Valley and Thomas Streets for girder settings from 11 p.m. Friday to 10 a.m. Saturday.
The closures are part of a busy weekend of road work. Be sure to plan ahead and check traffic conditions before you head out.
Construction on the SODO on-ramp to northbound State Route 99 will require several traffic closures near Seattle’s stadiums this weekend. Additionally, the St. Patrick's Day Dash will close a both directions of Aurora Avenue North/SR 99 north of downtown on Sunday morning.
Closure details – Friday, March 14 – Monday, March 17
Fans heading to Saturday’s Sounders FC match at CenturyLink Field should not be alarmed. Construction crews scheduled a break in the closures to ease traffic before and after the match.
The construction closures are part of a series of changes to the routing of SR 99 lanes and ramps around the SR 99 tunnel construction zone west of the stadiums. This weekend crews working for Seattle Tunnel Partners and WSDOT will complete work to move the South Royal Brougham on-ramp to northbound SR 99 closer to First Avenue South.
Drivers will begin using the relocated ramp Monday morning. This is the first step in a major traffic shift for the four-lane bypass that takes traffic around the SR 99 tunnel construction zone.
By this summer the bypass will split in two, with northbound SR 99 moving east and southbound SR 99 moving west. The traffic shift will provide space between both directions of the bypass for construction of lanes and ramps into and out of the SR 99 tunnel.
Washington State Department of Transportation bridge engineers have scheduled an additional in-depth inspection of the State Route 99 Alaskan Way Viaduct on Saturday, March 22.
During the viaduct’s most recent inspection on March 1, engineers observed new cracks, as well as movement and widening of existing cracks along girders and supports near Spring and Seneca streets. While the viaduct remains safe for travel, engineers need a second inspection to gather more information about the cracks before they can make repairs. The inspection requires a one-day closure that will take place Saturday, March 22. Details of the closure will be available soon.
During the March 22 inspection, engineers will conduct an in-depth evaluation of the area, perform tests to determine how the cracks respond to heavy loads on the viaduct, and look for other issues. They will also install monitoring devices on the columns to track the movement and growth of the cracks over time. They will use this data to help identify potential repairs. If additional work is needed, such as filling the cracks with epoxy, further closures will be required.
This section of the viaduct is more than a half-mile north of the current location of the SR 99 tunneling machine. While the cause of these cracks is still to be determined, it is not related to tunneling activity.
No other significant changes to the viaduct were observed during the March 1 inspection.
The Alaskan Way Viaduct is a 60-year-old structure that requires constant maintenance and attention to stay in service, which is why we inspect it four times each year. It is also why we are building a tunnel so it can be taken out of service before the next significant earthquake. Safety is our top priority and we will continue to work to ensure the viaduct remains safe for drivers.
Over the past two weeks, Seattle Tunnel Partners (STP) and Hitachi Zosen, the tunneling machine’s manufacturer, have been developing a plan to fix the seals on the machine. Today, STP notified us that they need to continue to work on the plan and expect to have it ready in the coming weeks. While we are anxious to receive a final plan, this is a complicated fix that requires significant calculation and planning. Their preferred option continues to be excavating a vertical shaft in front of the machine, driving the machine forward into the shaft and then making the needed repairs. At a media briefing this afternoon, Chris Dixon, STP’s project manager, estimated that this work will take six months or more.
On Thursday, the Alaskan Way Viaduct Replacement Program’s Expert Review Panel (ERP) released their 2014 report and recommendations. The Legislature has directed WSDOT to reconvene the panel annually since 2011 to review the program’s finance plan. While we are still reviewing the report, the panel has told us that they have confidence that the project can be successfully built.
This weekend, the Alaskan Way Viaduct will close for its semi-annual inspection. We inspect the viaduct four times a year and two of those inspections require a full closure of the structure. WSDOT bridge crews will close both directions of SR 99 between Denny Way and South Spokane Street from 6 a.m. to 6 p.m. Saturday and Sunday, March 1 and 2. During the inspection, crews will measure existing cracks, look for new ones, check for structural movement and evaluate the integrity of the viaduct’s foundations. Inspection results will be available in mid-March. Crews will also close both directions of SR 99 from Valley Street to the south end of the Battery Street Tunnel from 10 p.m. Friday to 6 a.m. Sunday to shift SR 99 lanes to the east side of SR 99 just north of the Battery Street Tunnel.
There were several reports in the media this week about the viaduct settling due to construction. We’ve done a significant amount of work to reinforce and maintain the viaduct over the years. Immediately after the Nisqually quake, we repaired damaged support columns and expansion joints to make the structure safe and functional. As discussions about how to replace the waterfront section of the viaduct continued, we implemented an automated closure system that consists of traffic gates at all viaduct access points controlled by an earthquake detection system. When the bored tunnel was selected as the preferred option and it was determined it would pass beneath the viaduct, we made strengthening portions of the structure near the tunnel route a requirement of the tunnel contract. STP has since implemented those requirements.
In addition, we have more than a hundred monitors on the structure so that we can watch the structure’s behavior in real time. Safety is our number one priority and we will not let the traveling public use the facility if the structure settles to unacceptable levels.
We’ve received questions from the public about whether the tunnel will open on time. The short answer is that Seattle Tunnel Partners (STP), our design-build contractor, is responsible for opening the tunnel to traffic by a date included in the design-build contract with WSDOT. STP is working with the machine’s manufacturer to develop and implement a repair plan so that mining can begin again. In conjunction with that work, STP will provide an updated schedule for the overall project including the anticipated date for opening the tunnel to traffic.
How the tunnel opening date is described in the design-build contract
An initial construction schedule for the SR 99 Tunnel Project was developed in 2010 when WSDOT released a Request for Proposals (RFP) and bidders responded. In the RFP, WSDOT stated that the winning contractor had to open the tunnel to traffic by Nov. 1, 2016. Extra points were given in the RFP evaluation process to bidders who could open the tunnel earlier than Nov. 1, 2016.
As part of its successful bid on the project, STP proposed opening the tunnel on Dec. 21, 2015, 316 days earlier than the RFP requirement. This date was based upon an assumed notice to proceed of Aug. 15, 2011. The actual notice to proceed was provided on Aug. 23, 2011, resulting in a revised tunnel opening date of Dec. 29, 2015. This milestone can be changed through a formal process known as a change order. As an example, a change order has been approved giving STP four additional working days due to inclement weather. As a result, the current opening of the tunnel to traffic is scheduled for Jan. 2, 2016.
What happens if the contractor opens the tunnel early or late?
For each day STP opens the tunnel earlier than Nov. 1, 2016, it is eligible to receive $100,000 per day, up to a maximum of $25 million. Conversely, for each day STP works beyond the Jan. 2 opening date, absent a change order modifying that date, it will be subject to liquidated damages in the amount of $50,000 per day. This holds true until Nov. 1, 2016. If the tunnel opens to traffic after Nov. 1, 2016, liquidated damages under the contract increase to $100,000 per day, up to a maximum total of $75 million.
STP’s original construction schedule included 339 working days to mine the 9,300-foot-long tunnel, including time for maintenance and interventions. This was based on a planned production rate that was slower at first, but increased to nearly 40 feet per day – a pace that STP believes is conservative when the machine is functioning properly. The schedule was based on the assumption that mining would occur five days per week, 20 hours per day. A contractor can, and frequently does, make changes to its schedule. In this case, STP has indicated that its work days and hours could be adjusted to 24/7 if desired.
As owner of this project, one of WSDOT’s roles is to review the schedule to ensure it complies with the contract. We have asked STP to update its construction plan and provide an accurate representation of that plan in the schedule. As explained above, STP has an incentive to work to meet the contractual milestone of opening the tunnel to traffic by Jan. 2, 2016.
Keeping the Alaskan Way Viaduct safely open to traffic during SR 99 tunnel construction is a top priority. It’s one of the main reasons we’re boring a tunnel – to minimize disruption at the surface as we replace the viaduct.
Recent media reports have stated that ground settlement due to tunnel construction could cause us to close the viaduct. These reports are inaccurate.
The viaduct is still vulnerable to earthquakes, but it remains safe for everyday use. The viaduct settled as a result of the Nisqually earthquake and we strengthened the viaduct in those areas so it remains safe for drivers.
We have no plans to close the viaduct until after the tunnel opens to traffic. Crews inspect the structure four times per year – the next inspection is scheduled for this weekend – and have taken a number of steps to protect it during construction.
We anticipated some ground settlement would occur during construction of the tunnel, which is taking place near the viaduct. That is why the viaduct has been strengthened in this area and more than 100 monitors have been installed on the viaduct to measure how much the ground beneath the structure moves.
Those monitors told us that the viaduct settled up to four-tenths of an inch at one location along the viaduct near where tunnel construction is underway. This settlement is well within the limits established by WSDOT’s structural engineers.
We will continue to carefully monitor the viaduct during construction and will take additional steps to reinforce the viaduct if needed.
We’ll be posting additional details soon about the work we’ve done to protect the viaduct. In the meantime, please feel free to contact us if you have questions or concerns.
On Friday, Feb. 21, Seattle Tunnel Partners spoke to the media about their plans to repair or replace the seal system that protects the SR 99 tunneling machine’s main bearing.
As expected, they will access the seal system through the front of the machine by digging a 100-foot-deep by 80-foot-wide shaft. Other details about the shaft and plan for fixing the seals will not be available until next week when experts from the machine’s manufacturer, Hitachi Zosen, arrive from Japan to help finalize the plan. STP has received proposals from various firms to design the shaft and will likely select a firm next week.
While STP has shared their preferred method for accessing the seal system, they are waiting until after their meeting with Hitachi to provide WSDOT with an official plan. Because this is a design-build contract, STP and their machine manufacturer are responsible for developing and implementing the plan to fix the machine and resume tunneling.
Drivers can expect an assortment of closures this weekend on or near State Route 99 at the south end of downtown Seattle.
The closures signal changes coming to the routing of SR 99 lanes and ramps around the SR 99 tunnel construction zone west of the stadiums. Crews working for Seattle Tunnel Partners and WSDOT are moving the South Royal Brougham on-ramp to northbound SR 99 closer to First Avenue South. This weekend’s closures will help them build a section of the new ramp alignment.
Crews will shift traffic onto the rerouted South Royal Brougham Way on-ramp by early spring. It’s the first step in a major traffic shift for the four-lane bypass that takes traffic around the SR 99 tunnel construction zone.
By this summer the bypass will split in two, with northbound SR 99 moving east and southbound SR 99 moving west. The traffic shift will provide space between both directions of the bypass for crews to continue building lanes and ramps into and out of the SR 99 tunnel.
Seattle Tunnel Partners (STP) informed WSDOT today that they expect to receive a plan on potential repairs to the SR 99 tunneling machine from the machine’s manufacturer Hitachi Zosen by the end of this month. This will include a schedule for how long the repair work would take. Earlier this week, STP told us the plan may be completed by the end of the week, but said today more time is needed for the Hitachi to prepare it.
It appears likely that repairs will be made by digging a shaft from the surface so the machine can be entered from the front. Entering the back of the machine would require removal of more equipment and likely take longer. STP will begin work next week on the design of the shaft so if that option is selected, some of the necessary work will already be underway.
We will post additional information as we receive it from STP.
Todd Trepanier, WSDOT’s administrator for the Alaskan Way Viaduct Replacement Program, and Chris Dixon, project manager for Seattle Tunnel Partners spoke with reporters about the status of the SR 99 tunneling machine for more than an hour on Tuesday, Feb. 11.
Video of the news conference is available on YouTube.
This evening Seattle Tunnel Partners (STP) informed WSDOT and responded to a media inquiry that it is still conferring with its experts to determine how to repair or replace the broken seals surrounding the main bearing of the SR 99 tunneling machine.
Replacing the seals is a complicated process and STP is working closely with Hitachi Zosen, the tunneling machine’s manufacturer, to determine the best path forward. They are looking at two ways to access the seal area: through the back of the machine or by drilling an access shaft from the surface in front of the machine. Either way, this process will take months. They expect to make a decision by the end of the week, and once they do, we will share that information with the public.
STP has not yet fully determined the cause of the seal problems and to date, they have not shown any evidence that suggests the state or taxpayers will be responsible for cost overruns associated with these repairs. We have requested and expect detailed plans on how the repairs will be made and how STP can recover lost time on the tunneling project.
Since the machine is stopped and repairs need to be made, STP has also informed the City of Seattle that they can proceed with seawall replacement construction near the machine’s current location.
Previous updatesJan. 21, 2014 update – Hyperbaric inspections continue
As we reported earlier this week, Seattle Tunnel Partners (STP) pushed the SR 99 tunneling machine forward approximately 2 feet on Tuesday, Jan. 28. Moving the machine forward allowed crews to further test the functionality of the machine and determine if they could resume full-production mining. It also created sufficient space to build the next concrete tunnel liner ring on Wednesday, Jan. 29.
When the machine moved forward, crews saw indications of above-normal temperature readings in part of the machinery, similar to readings encountered before crews initially decided to stop mining on Dec. 6. On Wednesday, STP made adjustments and mined an additional 2 feet. The above-normal temperatures persisted, and STP made the decision to stop and perform further evaluations.
Over the next week, outside tunneling experts brought in by WSDOT will meet with the WSDOT and STP project teams to review the situation and determine the best path forward.
STP crews and tunnel engineers are operating the world’s largest tunneling machine in complex conditions. Although their investigations to date have provided a great deal of information, we will not be able to definitively identify the issue or issues facing the machine until tunneling experts complete their review. We will provide additional information as it becomes available.
Seattle Tunnel Partners pushed the SR 99 tunneling machine forward approximately 2 feet today. Doing so allows crews to build the next concrete ring of the tunnel. Workers are now testing systems and evaluating the machine to see what maintenance might be needed before they resume tunneling.
Seattle Tunnel Partners is expecting to restart operations of the SR 99 tunneling machine this week.
Crews will finish inspections of the excavation chamber and cutterhead by the morning of Tuesday, Jan. 28. This will mark the completion of the hyperbaric intervention work at this time. As of Sunday evening, Jan. 26, crews had performed 36 hyperbaric interventions, totaling 134 hours over 10 days.
The first step after the hyperbaric interventions are completed is to advance the machine by 2 feet and build the next tunnel ring, which was in progress before the machine was stopped on Dec. 6. These 2 feet of mining and the ring build will be followed by an evaluation of the machine and its operating systems. This is necessary because the machine’s systems have been idle for seven weeks. The results of the initial mining and the extent of any required maintenance will determine when mining resumes.
Once mining resumes, the next critical milestone will be arriving at the third and final safe haven. This safe haven is approximately 500 feet ahead of the machine’s current location and was proposed by the contractor as a controlled environment for maintenance prior to mining under the Alaskan Way Viaduct and downtown Seattle. WSDOT plans to close SR 99 while tunneling occurs under the viaduct.
While we understand the interest in knowing the reasons why mining was stopped in December, it will take time to review the results of the hyperbaric interventions and consult with tunneling experts advising WSDOT. We will continue to provide the public with information as we have it and work with the contractor to ensure that the machine is ready to begin mining under downtown Seattle.
Regular updates will be provided this week when new information is available.
Jan. 23, 2014 update – Hyperbaric investigations continue
On Monday, Jan. 27, we opened a new overpass to the west of Seattle’s stadiums. The overpass allows traffic to bypass a busy railroad track that crosses South Atlantic Street. Before the overpass, train activity often blocked traffic for extended periods, which not only slowed truckers traveling to and from the Port of Seattle, but also created backups that stretched onto Seattle streets and Interstate 90. The overpass saves truckers as much as 20 minutes of travel time between the port and I-5 or I-90.
The section of Atlantic beneath SR 99 will remain closed to through traffic until the SR 99 tunnel opens to traffic. Drivers will now use the new overpass to travel in both directions between Atlantic and Alaskan Way South.
Later this winter, crews will complete improvements to the bicycle and pedestrian path on the west side of SR 99 between Atlantic and South King streets.
The north leg of the overpass will open to the public after the tunnel opens and will eventually link traffic to the new Alaskan Way and Seattle waterfront.
Crews have now performed 17 hyperbaric sessions inside the SR 99 tunneling machine’s excavation chamber, and in front of its five-story-tall cutterhead. That’s a total of 68 hours of hyperbaric work since crews started inspections on Jan. 17. Crews have not found anything significant beyond what we reported on Jan. 21.
Prepare to say goodbye to a bottleneck that has long frustrated drivers near the Port of Seattle’s busiest freight terminal.
On Monday, Jan. 27, we'll open a new overpass to the west of Seattle’s stadiums. The overpass will allow traffic to bypass a busy railroad track that crosses South Atlantic Street and will help freight and drivers move faster and more reliably through the area. Today, train activity often blocks traffic for extended periods, which not only slows truckers traveling to and from the Port of Seattle, but also creates backups that stretch onto Seattle streets and Interstate 90. The overpass could save truckers as much as 20 minutes of travel time between the port and I-5 or I-90.
To complete the connections between the overpass and nearby streets, crews must close South Atlantic Street and the State Route 99 off-ramp to Atlantic this weekend. Both closures will start at 4 a.m. Saturday, Jan. 25. The overpass and off-ramp will open to traffic by 5 a.m. Monday, Jan. 27.
The section of Atlantic beneath SR 99 will remain closed to through traffic until the SR 99 tunnel opens to traffic. Drivers will instead use the new overpass to travel in both directions between Atlantic and Alaskan Way South.
Later this winter, crews will complete improvements to the bicycle and pedestrian path on the west side of SR 99 between Atlantic and South King streets.
The north leg of the overpass will open to the public after the tunnel opens and will eventually link traffic to a newly rebuilt Alaskan Way and Seattle waterfront.
Since hyperbaric inspections began on Jan. 17, crews from Seattle Tunnel Partners (STP) have spent more than 35 hours inside the excavation chamber gathering information about what might have caused increasing resistance at the front end of the machine before tunneling was stopped on Dec. 6.
While the inspections are underway, it is too early to speculate on what led to the tunneling stoppage.
Over the weekend, crews inspected a portion of the cutterhead as well as the cutting tools they were able to access. They also cleaned the spokes and removed a bent piece of metal well casing and plastic PVC pipe. Crews also identified a large boulder or piece of concrete material in a cutterhead opening.
The information from the inspection along with other data will be reviewed by a tunneling operation task force, which has been convened by WSDOT.
These inspections are methodical. Workers are going spoke by spoke to clean off the tunnel muck, inspect parts and make necessary repairs.
Air is being pumped into the chamber to stabilize the ground in front of the machine so crews can safely work in areas that would otherwise be filled with soil and water. After pressure in the chamber was lost, crews spent Sunday re-establishing the required air pressure in the chamber so inspection work could continue. This is a routine occurrence in hyperbaric interventions. A detailed description of this type of work is included in our Jan. 14 update.
Keeping workers safe is everyone’s top priority. STP has a number of safeguards in place to protect crews as they perform their work within the machine. Working under hyperbaric conditions is difficult, but it’s normal within the tunneling industry and has been done on other projects all over the world.
This afternoon, crews entered and began inspecting the SR 99 tunneling machine’s excavation chamber. Air is being pumped into the chamber to stabilize the ground in front of the machine so crews can safely work in areas that would otherwise be filled with soil and water. A detailed description of this type of work – known in the tunneling world as a hyperbaric intervention – is included in our Jan. 14 update.
Keeping workers safe is everyone’s top priority. Our contractor, Seattle Tunnel Partners (STP), has a number of safeguards in place to protect crews as they perform their work within the chamber. Working under hyperbaric conditions is difficult, but it’s normal within the tunneling industry and has been done on other projects all over the world.
The goal of STP’s inspection is to learn, definitively, what caused the issues that slowed the machine’s progress. Once they know what's wrong, they can develop a plan to address the issue and resume tunneling. The inspection will likely take several days.
One reason Seattle Tunnel Partners (STP) was selected to build the SR 99 tunnel was because of their tunneling expertise. In particular, we were drawn to one component of their proposal, which involved building a protected underground area along the first 1,500 feet of the tunnel drive.
In addition to protecting the viaduct and other structures in this very shallow, challenging section of the route, this protected area allows the contractor to test all functions of the tunneling machine and its operations prior to tunneling under downtown Seattle.
Letter to STP
We’ve had concerns about the SR 99 tunneling machine’s operations and critical systems since its launch on July 30, 2013. We have discussed these concerns with STP frequently over the past five months.
This week, we sent a formal letter stating our concerns and asking STP how they plan to address them. A copy of the letter won’t be made public because it could be the subject of a potential future litigation between WSDOT and the contractor.
Our request for information is not an attempt to tell STP how to do their work. If we did that, we could bear responsibility for the cost and risks associated with those actions. We asked for the following by close of business Wednesday, Jan. 15:
Bringing in outside experts
We are assembling a panel of tunneling experts to review, evaluate and provide opinions on the following:
The panel will also provide a template approach to be adopted for addressing similar, critical events that may occur in the future. We have requested that STP accommodate these experts as they evaluate intervention and repair operations and assess the machine’s ability to resume tunneling.
We’ll continue to provide you with updates as we move forward.
Construction of new ramps that will connect the existing lanes of SR 99 to the north entrance of the future SR 99 tunnel will get underway this winter.
The Washington State Department of Transportation awarded the $41.6 million contract to Guy F. Atkinson Construction, LLC of Renton, Wash. The contract is nearly $4.5 million under WSDOT’s estimate.
The SR 99 North Access Connection Project will connect the SR 99 tunnel’s north entrance at Harrison Street to the existing roadway north of the Mercer Street bridge. It will also build new on- and off-ramps at Republican and Harrison streets, extend Sixth Avenue North between Harrison and Mercer streets, and improve water and sewer lines in the area.
There is already heavy construction in the neighborhood. Our tunnel contractor, Seattle Tunnel Partners, is building the tunnel’s north entrance and the Seattle Department of Transportation is building the new Mercer Corridor. We will work closely with our partner agencies to minimize impacts on the traveling public. Visit our interactive map of the north access project to see how construction will progress.
When you're sick, you go to the doctor. Based on your symptoms, the doctor checks for obvious clues about what might be ailing you. If his initial search doesn't yield the answer, he takes additional steps. He might run more thorough tests or send you to a specialist who has the tools and knowledge to give you an accurate diagnosis and develop a treatment plan.
When crews operating Bertha, the SR 99 tunneling machine, experienced increasing resistance at the front of the machine, they stopped tunneling. They started looking for obvious things that could have slowed the machine's progress. As the weeks went on, the search intensified. They found clues, including part of an 8-inch-diameter steel pipe inside the machine's excavation chamber.
But obvious things, it turns out, aren't necessarily at the root of this issue. It's time to see the specialist. Or, to use tunneling lingo, it's time to go hyperbaric.
Don't worry. If you don't know what "going hyperbaric" means, you're not alone. Cryptic as it appears, the word "hyperbaric" actually does a decent job of explaining itself -- even if you can't pinpoint its meaning, you get the sense it involves something complicated. And you're right.
Simply put, hyperbaric refers to pressure that is greater than the atmosphere we live and breathe in every day. In the tunneling world, it means using air pressure to stabilize the ground in front of a tunneling machine so crews can safely work in areas that would otherwise be filled with soil and water.
To understand why this is so complicated, it helps to consider Bertha's anatomy. At the very front of the machine lies the giant green cutterhead that grinds its way through the earth. All that dirt (and whatever else the machine encounters underground) gets pushed into the 5-foot-wide excavation chamber. There, it is mixed with water and soil conditioners that make it easier to extract through the machine's screw conveyor. Since Bertha stopped, the excavation chamber has been filled to the brim with water, muck and more. Crew members have peeked through a hatch into the chamber, but they can't safely go inside and work unless they create hyperbaric conditions.
Building a bubble for Bertha
Our contractor, Seattle Tunnel Partners, spent much of December lowering the water pressure in and around the machine. The next step is to create an air bubble within the excavation chamber so crews can inspect Bertha more closely. The bubble is created by injecting bentonite, a soil conditioner with the consistency of thick chocolate milk, into the chamber. As the chamber fills, the mixture flows outside the cutterhead to fill the 1-foot-wide space between the ground and the front of the cutterhead.
The goal is to create a protective bentonite membrane around the front of the machine. Once the membrane is in place, crews will fill the chamber with compressed air. The air will push the bentonite mixture toward the dirt in front of Bertha as we turn her giant screw below to pull out tunnel muck and create more space for the expanding air bubble. Eventually, the bubble will fill up the upper half of Bertha’s excavation chamber. When crews are confident the ground and air pressure are stable, they'll go inside to perform their work.
Before they enter the chamber, crews will have to adjust their bodies to the pressure created by the compressed air. It's the same process scuba divers go through during the course of an underwater dive. Our workers don't need diving gear. They simply crawl inside specialized pressure chambers built into the machine for a few minutes until their bodies are ready for the conditions inside the chamber.
Five workers will work in the excavation chamber at a time. Each crew will spend three hours inspecting Bertha and working to get her moving again. On the way out of the excavation chamber, they'll spend another hour in the pressure chamber readjusting to atmospheric pressure before the end of their shift. Each crew member can only enter the pressurized excavation chamber once every 24 hours.
The goal of going hyperbaric is to learn, definitively, what caused the issues that slowed the machine. Once Seattle Tunnel Partners knows what's wrong, they can come up with a plan to address the issue and resume tunneling.
We recognize that this process isn't moving as quickly as some would like. The reason for this is that, like going hyperbaric, none of this is easy. On the contrary, tunneling is incredibly complicated, Bertha is incredibly complicated, the ground conditions where she's located are incredibly complicated – you get the idea. This is challenging work. The safety of our workers and the success of our work are paramount. A thoughtful approach is just what the doctor ordered.
Today, crews filled in the third of three shafts drilled last week in front of Bertha, the SR 99 tunneling machine. The shafts were drilled to further identify the limits of any metal in front of the machine and remove as much of it as possible. Plans to drill a fourth shaft have been put on hold as crews prepare to perform an inspection within the machine’s excavation chamber.
Crews are also continuing to change cutting tools and perform other maintenance within the machine.
Yesterday afternoon, drilling of an exploratory shaft indicated the possible presence of an object in front of Bertha, the SR 99 tunneling machine. To explore further, a crew member was lowered approximately 60 feet down into the shaft. His visual inspection was inconclusive. Additional inspections are taking place today.
Crews have completed drilling three of four shafts being used to further identify the limits of any metal in front of the machine and remove as much of it as possible. If no objects are detected or removed from the shafts, the shafts will be filled to form part of an underground barrier that will create a safe environment for workers to enter the machine’s excavation chamber.
It’s still too early to determine the cost or long-term schedule implications of this issue. We’ll continue to work with Seattle Tunnel Partners to determine ways to make up time lost during the blockage. Our focus is now on addressing this issue safely and in a timely manner so we can resume tunneling as soon as possible.
On Jan. 9, 2014, crews continued drilling the third of four planned exploratory shafts in front of Bertha, the SR 99 tunneling machine. These shafts are being installed where earlier probing detected metal in front of the machine.
The shafts are being used to further identify the limits of any metal in front of the machine and remove as much of it as possible. If no objects are detected or removed from the shafts, the shafts will be filled to form part of an underground barrier that will create a safe environment for workers to enter the machine’s excavation chamber.
So far, no objects have been detected during drilling of the shafts.
Reminder about the steel pipe
Much attention has been focused on the steel pipe fragment that was seen protruding through an opening in the machine’s cutterhead on Jan. 2. While we believe the pipe may be a contributing factor to the tunneling slowdown, it’s important to remember that the overall cause won’t be known until our investigation is completed.
It’s also important to remember that the work we’re doing is very difficult. For the safety of crews and the long-term interest of the project, we must act carefully and thoughtfully. Earlier today, a WSDOT spokesperson said in a media interview that the machine may not begin to operate again for at least a month. In fact, it is too early to speculate on the schedule until we receive information from our contractor.
We recognize that this is very important project and that all Washingtonians have a strong interest in seeing it succeed. We (and Bertha) will continue to provide regular updates about our progress.
On Jan. 8, crews finished drilling the second of four planned exploratory shafts in front of Bertha, the SR 99 tunneling machine. The shafts are being used to further identify the limits of any metal in front of the machine and remove as much of it as possible.
If an object is encountered, crews will try to identify and remove it from the ground. If no objects are detected or removed from the shafts, the shafts will be filled to form part of an underground barrier that will create a safe environment for workers to enter the machine’s excavation chamber.
During drilling of the first shaft, crews believe they may have encountered an obstruction, but couldn’t tell for sure because the drill quickly passed by it on the way to its final depth of 118 feet. No objects were encountered during drilling of the second shaft.
The top of the machine is located about 60 feet below the surface between South Jackson and South Main streets, to the west of the State Route 99 Alaskan Way Viaduct. Wells installed near the machine last month by our contractor, Seattle Tunnel Partners, are continuing to pump water out of the ground at a steady rate. Crews have completed inspecting and cleaning out the machine’s screw conveyor, which remains fully functional.
Crews are also continuing to gather information about any other factors that might have contributed to the stoppage of tunneling last month. The overall cause of the tunneling slowdown will not be known until the investigation is completed.
Crews spent the weekend preparing the ground around Bertha, the SR 99 tunneling machine, for further investigation. They started by injecting a low-strength blend of cement and sand into voids that had developed in the ground in front of the machine. The voids were expected due to the recent removal of water and soil from the machine’s excavation chamber, which was necessary for crews to safely inspect it last week.
With all of the voids now filled, crews will be able to better assess the situation. Late this morning, they started drilling 5-foot-diameter shafts in front of Bertha. These shafts are being installed where earlier probing detected metal in front of the machine.
The plan is to further identify the limits of any metal in front of the machine and remove as much of the metal as possible. Crews are also continuing to gather additional information about any other factors that might have contributed to the obstruction that stopped tunneling last month. The overall cause of the tunneling slowdown will not be known until the investigation is completed.
A lot of attention has been focused on the 8-inch-diameter steel pipe that was discovered during last week’s inspection, but other interesting objects have passed through the machine.
Here’s a shot of some boulders that made their way through Bertha’s conveyance system before her progress was slowed, as well as several pieces of metal that are believed to be part of the pipe.
A second photo shows a 57-foot-long section of pipe that’s now lying in the construction yard. This section of the pipe was pulled from the ground after it was struck by the machine in early December.
It was a busy holiday season for crews working to get Bertha, the SR 99 tunneling machine, digging again. While we still can’t say for sure what halted the machine on Dec. 6, we’re much closer to finding an answer than we were when all of this started.
Here’s a recap of what crews have been up to since the blockage occurred:
STP is considering several options to remove the steel pipe and identify other potential obstructions.
While Bertha is stopped, other work is taking place. This includes:
It’s too early to speculate about the cost or long-term schedule implications of this issue. We’ll continue to work with STP to determine ways to make up time lost during the blockage. Our focus is now on addressing this issue safely and in a timely manner so we can resume tunneling as soon as possible.