Sound Transit has taken the first step in finding a contractor to complete the 2,490ft (760m) long Downtown Bellevue Tunnel project, as part of its East Link light rail extension, in Seattle, USA. Bids for the tunnel contract – which has been estimated in the region of $130 to $180 million – are due on August 6th.
The East Link Projects is a voter-approved $2.8 billion, 14-mile extension of the existing light rail transit (LRT) system from downtown Seattle, across Lake Washington via I-90, serving Mercer Island and the cities of Bellevue and Redmond to the east. Construction is scheduled to begin this fall and run through 2021.
Sound Transit is currently finalizing the design for the extension. Final design of the easternmost seven miles of the line – including the tunnel – was awarded to the HJH Team, a joint venture comprising HNTB, Jacobs Engineering and Hatch Mott MacDonald. The tunnel will be approximately 2,490ft (760m) in length, with short 250ft (75m) cut and cover portals and a central SEM section of about 1,990ft in length.
Work for the contract will begin with preparation of the south portal staging area. Activities will include demolition of existing structures and the existing portion of SE 1st Place. The contract also includes installation of a temporary sound wall around the south portal area prior to heavy civil work, including excavation and construction of retaining walls and the portal box structure. The tunneling operation is anticipated to be primarily from the south portal. A mid-tunnel access shaft and adit will also be constructed using SEM/NATM.