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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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