A Message from WSDOT Regarding Ground Settlement

BerthaGood afternoon,

I wanted to send a quick note to let you know the latest information about settlement in Pioneer Square.

We have told you about our settlement monitoring system that we installed as part of the SR 99 Tunnel Project. As we publicly announced last Friday, STP surveyors detected over one inch of ground settlement near the pit Seattle Tunnel Partners is building to access and repair the tunneling machine. We have also seen settlement on the Alaskan Way Viaduct and some of the buildings that we are monitoring; the amount of settlement lessens in the surrounding area.

Most of the settlement we’ve detected has been uniform, which usually means little to no damage to buildings and utilities. Engineers have been walking through the Pioneer Square neighborhood since we first learned of the new settlement. They have not seen any signs of new damage so far. An inspection team that includes an architect with historic building experience has been conducting interior building surveys since Monday and will continue over the next couple of weeks. If you have seen any recent changes in your building, such as new cracks or lengthening of cracks, sticking doors and windows or utility problems, please email us so we can set up an appointment.

Additionally, we have stepped up our monitoring frequency. Deep survey control points are checked approximately every other day and buildings and various points on the ground are surveyed once a day. Since Dec. 1, STP has not seen any appreciable change in settlement. Based on this, it appears that additional settlement is not occurring, though we will continue to closely monitor the situation.

At this time, Seattle Tunnel Partners is maintaining their dewatering system – and water levels remain static. However, they have stopped excavation until we can verify the new data. We will let you know when excavation resumes.

As for the crack in King Street, Seattle Tunnel Partners checked the site with ground-penetrating radar Thursday afternoon. While we are still awaiting the report, no voids were detected under the pavement.

If you have concerns about your building, property or utilities, please do not hesitate to call our hotline at 1-888-298-5463 or email us at viaduct@wsdot.wa.gov.

Regards,

Todd

 

Todd V. Trepanier, PE
Administrator
Alaskan Way Viaduct Replacement Program

Tunnel Project Update

BerthaWSDOT and Seattle Tunnel Partners conducted additional survey work early Sunday morning (12/7/2014) 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.

Alaskan Way Viaduct Replacement Project Update – September 2014

BerthaMilepost 31 Speaker Series

Bertha and Progress on the SR 99 Tunnel Project

Seattle Tunnel Partners, the contractor hired by WSDOT to design and build the SR 99 tunnel, is working to repair the SR 99 tunneling machine. Join us to learn more about STP’s plan to resume tunneling by the end of March 2015, and learn about the other work happening to replace the viaduct.

6 – 6:30 p.m.
Friday, Sept. 5
Milepost 31, 211 First Ave. S., Seattle
Admission is free.

 

Seattle Tunnel Partners progress update: Construction of the access pit’s underground walls wraps up, preparation for dewatering begins

With fall just around the corner, 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 they have completed all of the piles for the circular pit. 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.

STP still expects to resume tunneling in March 2015. For a better view of construction, check out our time-lapse camera, or view photos of recent construction on Flickr.

Additional resources

Alaskan Way Viaduct Replacement Program News – August 2014

BerthaTopics:

Bertha update – Construction of the access pit’s underground walls will continue through August

Earlier this week, 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 pit’s 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:

  • Shipping repair pieces: The new main bearing has arrived in Seattle and will be assembled closer to the time it’s needed, likely this fall.
  • Manufacturing repair pieces: Other repair pieces, such as the new outer seal ring, the thrust seal ring and bearing block are nearing completion. After these pieces are fabricated and inspected, Hitachi Zosen will ship them to Seattle.
  • Assembling a 300-ton crawler crane: This crane will be used to help assemble the 600-ton crawler crane. Pieces of that crane will arrive in September and assembly will begin shortly thereafter.
  • Assembling a 600-ton crawler crane: This crane will be used to assemble the modular lift tower (massive red crane) that will lift the largest pieces of the machine from the access pit. Parts of that crane will also arrive in September and assembly will begin in late September.
  • Assembling the 2,000-ton modular lift tower: Starting in late July and continuing through fall, crews will begin to stage the modular lift tower. Parts of the modular lift tower will arrive over the next several months beginning in late July.

We will continue to update you on STP’s efforts to resume tunneling by March 2015. You can watch the access pit take shape on our time-lapse camera, and view photos of recent construction on Flickr.
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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:

  • Utility work at Harrison Street.
  • Concrete panel replacement in SODO.
  • Expansion joint repairs on the Alaskan Way Viaduct near the Seneca Street off-ramp.
  • Ivy removal from the viaduct.

Closure information

Drivers should plan ahead for SR 99 closures from Friday night, Aug. 22 to Wednesday morning, Aug. 27. View a map of the closure.

  • From 10 p.m. Friday, Aug. 22 to 5 a.m. Monday, Aug. 25, SR 99 will be closed in both directions from the West Seattle Bridge to Valley Street.
    • Northbound SR 99 will be open from South Royal Brougham Way until midnight on Friday, Aug. 22 for exiting Seahawks traffic.
  • From 5 a.m. Monday, Aug. 25 to 5 a.m. Wednesday, Aug. 27, SR 99 will be closed in both directions from the south end of the Battery Street Tunnel to Valley Street.

Driver tips

Travelers who use SR 99 should consider the following:

  • Allow plenty of extra time and expect additional congestion on alternate routes including I-5 and surface streets.
  • Leave early or delay your trip to avoid traveling during peak commute periods in the morning and afternoon.
  • Delay or reschedule discretionary trips.
  • Consider telecommuting.
  • Choose an alternative travel mode such as King County Metro, share a ride in a car or vanpool, or walk or ride a bicycle. 

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.

  • The Seattle traffic page contains updated road information including links to traffic cameras.
  • The travel alerts website provides real-time information about blocking incidents.
  • WSDOT’s mobile app offers information for travelers on the go.
  • @wsdot_traffic provides Twitter updates about travel issues.
  • 5-1-1 offers traffic updates.
  • The What’s Happening Now page chronicles closures and issues affecting travelers.
  • Learn more about your commute and travel choices.

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Milepost 31 Speakers Series – Bertha and progress on the SR 99 Tunnel Project

Seattle Tunnel Partners, the contractor hired by WSDOT to design and build the SR 99 tunnel, is working to repair the SR 99 tunneling machine. Join us to learn more about STP’s plan to resume tunneling by the end of March 2015, and learn about the other work happening to replace the viaduct.

  • 6 – 6:30 p.m.
  • Thursday, Aug. 7
  • Milepost 31, 211 First Ave. S., Seattle
  • Admission is free

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