As Washington State Dept. of Transportation officials look toward a fall 2018 opening of the 1.7-mile-long bored tunnel under downtown Seattle that will replace the aging 1953-opened Alaskan Way Viaduct—also part of State Route 99—the final contract in the $3.3-billion project to tear down the viaduct was awarded to Kiewit Infrastructure West.

WSDOT says some of the details about the project won’t be known until the contract gets finalized and the contractor receives approval to begin design work, such as the exact specifics about the timing of the project and just how demolition and decommissioning will work—expect a full ENR story on the project upon finalization of the contract. Even still, WSDOT says the majority of the viaduct demolition will occur in 2019.

The design-build contract, which requires the contractor to provide expertise in the demolition strategy, is valued at $93.7 million and was chosen based on an “apparent best value bid,” a combination of points received for technical proposals and price.

“We are excited to be so close to removing the seismically vulnerable viaduct and ushering in a new era on Seattle’s waterfront,” says Brian Nelson, WSDOT’s Alaskan Way Viaduct Replacement Program administrator. “It will be challenging to tear down a major highway in the heart of a booming city, but we’re looking forward to getting it done safely and as quickly as possible.”

While WSDOT and Kiewit work out the final contract details, Seattle Tunnel Partners wraps up work on the tunnel, anticipated to open this fall. Before the tunnel can open a closure of the viaduct is needed to realign SR 99 and ramps at the tunnel portals, a process that could last a few weeks. This closure will serve as the permanent retiring of the viaduct.

WSDOT says that after the viaduct permanently closes, contractors may start limited demolition work, meaning late 2018 could see the start of the removal of the viaduct.

Along with the removal of the viaduct, the Kiewit contract includes filling in the 1954-built, 2,000-ft Battery Street Tunnel, currently part of the SR 99 alignment. It will take up to two years to remove equipment and fill in the Battery Street Tunnel. Battery Street will also require utility improvements.

Follow Tim Newcomb on Twitter at @tdnewcomb.