WHERE DOES IT FLOOD?

The North Branch flows along the border of Albany Park on the city’s North Side. Floods caused damage to hundreds of structures since 2008.

North Branch Chicago River

Area of flooding

North Shore Channel

FOSTER

SPRINGFIELD

94

ELSTON

LAWRENCE

PULASKI

KIMBALL

KEDZIE

MONTROSE

Feet

1,000

ALBANY PARK

WHERE IS THE TUNNEL?

The tunnel will run for 1 mile under Foster Avenue.

Tunnel

FOSTER

HOW BIG IS IT?

The tunnel is 18 feet in diameter and 150 feet underground. Once finished a total of 69,000 cubic yards of rock will have been removed, leaving a tunnel that can hold 1.6 million cubic feet of water.

Concrete 14 inches

Tunnel 18 feet

HOW DOES IT PREVENT FLOODING?

If water rises over the bank, it flows into an inlet at Springfield Avenue at the North Branch of the river.

Down to tunnel

Inlet

Floodwater

FOSTER

The water flows east, where it will come back to the surface and exit the outlet into the North Shore Channel near Albany Avenue.

Outlet

HOW IS THE TUNNEL BEING DUG?

Engineers are using an enormous hydraulic boring machine nicknamed “Keri,” built by German-based company Herrenknecht. It will cut the tunnel bit by bit. The machine was lowered down the outlet shaft and is boring the tunnel west toward Springfield Avenue.

PHOTO COURTESY CITY OF CHICAGO

HOW LONG WILL IT TAKE?