Seattle street closed after sinking concern

Transportation crews closed part of King Street at First Avenue South to investigate sinking Thursday afternoon, likely tied to the Bertha repair.

On Thursday, WSDOT released a new map that reveals settlement is far more widespread than previously explained. The map shows sinking detected as far north as a monitoring station at 3rd and Pike, a considerable distance from Bertha's repair pit. That sinking, of .11 inches, compares to 1.4 inches of settlement detected closer to the work site.

The map also shows deep benchmarks, measurements taken as deep as 120 feet, also detected movement. One of them, near CenturyLink Field, detected settlement of .64 inches.

At a city council briefing Monday, project administrator Todd Trepanier said "deep benchmarks are not supposed to settle," revealing how puzzling the sinking is to WSDOT experts.

State officials say 30 buildings in Pioneer Square sank about an inch. In a news conference Thursday, Mayor Ed Murray says that there is no reason to believe buildings are at risk.

State project leaders revealed the uneven settlement they discovered was around King Street in Pioneer Square, but did not actually cause any damage.

On Sunday, WSDOT revealed some of the settlement discovered was uneven, which is the most likely to cause damage.

On Friday the Washington State Department of Transportation disclosed the viaduct sank 1.25 inches, likely as a result of pumping out groundwater to build the pit to access and repair the broken tunnel machine Bertha.

The viaduct, which is vulnerable to earthquakes, has so far settled evenly, a reassurance about its structural integrity.

Two-thirds of the buildings that have settled are outside the zone where contractors have a sophisticated system of laser beams to detect any movement.

Project leaders say that's because the system was designed to check for impacts from tunneling itself, not from building a repair pit.

They said Monday they have hired outside consultants and are extending the monitoring system.

On Sunday evening WSDOT indicated its contractor, Seattle Tunnel Partners, planned to stop dewatering, phasing it out slowly in a safe manner.

On Monday afternoon that message had changed, with project administrators saying the decision about whether to stop dewatering has not yet been made while more data is gathered.

They said settling on the viaduct seems to have stabilized recently.

Todd Trepanier, project administrator, deferred questions on Monday about whether stopping dewatering would mean repair pit construction would also stop, saying that was a decision to be made by STP.

Councilmembers Jean Godden and Mike O'Brien were particularly concerned that WSDOT did not inform the council members sooner on Friday about the settlement.

"I've been on the phone with WSDOT -- what did they know, when did they know and what they're going to do about it," Godden told reporters.

O'Brien repeatedly pressed state officials to provide information about the threshold of allowable settlement on the viaduct.

They said there was no specific number and that it depended on conditions in specific places.

Increasingly concerned about transparency, council members requested that WSDOT officials return next Monday to brief them on the project and contingency plans if the viaduct has to be closed.

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