State officials will sign a $1.09 billion contract with Seattle Tunneling Partners (STP), a conglomerate of private construction firms, to build a deep-bore tunnel downtown at media event on Thursday, sources tell The Stranger. The Washington State Department of Transportation has not yet released details, nor returned calls to comment, but people familiar with the deal say that STP has won the bid without a challenge. On December 9, the state named STP the presumptive winner, but allowed a grace period for the competing bidder, Seattle Tunneling Group, to challenge the technical rating used in the evaluation.

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Seattle Tunneling Partners, which submitted a higher bid but won on technical merits (narrower portal, wider tunnel, and shorter timeline), is a joint venture of Dragados USA and Tutor Perini Corp, including Frank Coluccio Construction, Mowat Construction, HNTB Corp. and Intecsa. Lower Hudson Journal News reported last month that part of the presumptive team to dig the tunnel—Tutor-Saliba and Perini Corp., which combine to become Tutor Perini Corp, one of the members of Seattle Tunneling Partners—has a history of cost overruns and fraud allegations.

The signing will occur at the Port of Seattle office on Alaskan Way a 3:00 p.m.