Zoom Through Seattle's Nearly Completed SR-99 Tunnel

[Narrator] Remember that saga

in Seattle when Bertha the tunneling machine

got stuck under ground?

Well after four years

under the city, Bertha finally

broke through in April and this is the result.

This drone video shows

the nearly two mile tunnel

that's eventually going to move all the traffic

from an elevated highway

under the surface.

We're entering on the north side here

near Seattle's famous space needle headed South.

The tunneling disassembly pit is the hole

that engineers dug to pull Bertha the tunneling machine

out of the ground

when it's job was done.

One day, hopefully as soon as early 2019,

cars will drive this path.

The corbels, the foundations of the road

are 100 % complete and the top deck of the road

is 85 % done.

The tunnel is a double-decker so traffic headed North

will be on the bottom.

And the builders will bring

in prefabricated road panels

next month to start building that section.

South bound traffic will be up top.

It might not look like much yet

but this is the stage

when all the vital subsystems are going in

and being tested.

Things like emergency exits, fire suppression

and ventilation.

Crews are working

northwards from the south end,

that's why things are starting

to look a little more completed

as we fly through.

The cut-and-cover part is where

the tunnel is dug this part

of the tunnel as a pit

and then laid a roof cover over the top

rather than boring it with a machine.

That's how they build

the shallowest sections

like this that lead out

near the stadiums in Seattle.

As we look back, you can see

the elevated section of roadway

that just totally separates the city

from the waterfront behind

those yellow ventilation chimneys.

That it'll be demolished in 2020

when the tunnel is fully ready for traffic if everything

goes to plan from here onwards.