THIS WEEK, WE conclude our final walkabout on the Alaskan Way Viaduct with a stroll through the Battery Street Tunnel, which was completed in July 1954, a little more than a year after the viaduct’s opening ceremony. The tunnel connected the viaduct to Aurora Avenue, fulfilling the promise of an efficient, new Highway 99 to divert and reduce the snarl of downtown traffic.

Our historical photo records a City Engineering Department test of the tunnel’s ventilation system. Lined up in two northbound lanes are 180 cars and trucks of city and state employees, simulating the worst of traffic jams, idling their motors for 30 minutes (modern eyes might also note the pipes and cigarettes adding to the haze). Within minutes, 36 big fans were blowing enough fresh air into the tunnel that, “The amount of carbon monoxide in the air … would not be dangerous to a person after eight hours of exposure,” claimed city engineers.

On Feb. 2, 2019, I joined a line of ticket-holders stretching ’round the block to enter the viaduct via the Seneca Street offramp. Tens of thousands paid their last respects and bid a fond farewell — for some, a hearty good riddance — to the double-decked edifice admired for its spectacular, egalitarian views of Seattle and its waterfront. Gray skies clearing, the Hello/Goodbye Viaduct Arts Festival lined the upper deck with art exhibits, performers and food trucks.

Over the next few months, the half-mile-long Battery Street Tunnel will be filled to about 7 feet from its ceiling with rubble from the viaduct, then topped with low-density cellular concrete poured in through surface vents along Battery Street.

For our “Now” photo, we look north along the southbound lanes of the tunnel, on whose walls the group Vanishing Seattle projected an evocative 15-minute video of collected photos, movie clips and written memories of the viaduct. For more, visit vanishingseattle.org or #vanishingseattle on Instagram or Facebook. To experience the last commute on the viaduct in 360-degree video, please visit our blog, below.