Dive Brief:

• Seattle Tunnel Partners is pushing back against Washington Gov. Jay Inslee's order stopping tunneling on the $1.35 billion Alaskan Way Viaduct project, which developed a sinkhole when STP resumed tunnel boring operations in late December after a two-year hiatus, according to the Seattle Times.
• STP, a joint venture including New York-based Dragados USA and California-based Tutor Perini, said the order is unjustified because it is already addressing the problem by filling the hole with a mixture of 250 cubic yards of concrete and sand. STP said the root-cause analysis of the sinkhole that the governor and Washington State Department of Transportation demanded last week did not completely determine why the sinkhole formed.
• The tunnel-boring machine, Bertha, has only moved forward 190 feet since its 2013 breakdown and has moved a total of 1,280 feet since tunneling began.

Dive Insight:

A root analysis by STP maintained that potential reasons for the sinkhole as "a pre-existing void, a ground loss in the face of the (tunnel-boring machine), or a combination of both," the Times reported. The study went on to say that "stopping the (tunnel-boring machine) at its current location is not recommended and increases the risk of creating additional sinkholes."

An independent panel of experts will review STP's analysis, and WSDOT must issue written permission to STP before the company can resume tunneling.

STP maintains that Bertha should be allowed to tunnel at least 250 feet more to a concrete-lined rest stop where it can be inspected before continuing under the viaduct and Seattle's historic Pioneer Square.

In October 2015, the WSDOT announced it was suing STP for delays on the viaduct project. STP countered that the WSDOT failed to inform them about a 119-foot steel well casing in Bertha's path and said it was seeking additional compensation under the contract with WSDOT.

Tutor Perini recently announced a major 2015 revenue adjustment from $5.5 billion to $5 billion, and the company cited the Viaduct as one of the main reasons behind the losses.