After a year and a day, Nannie’s work is done.

The tunnel-boring machine, which was named after prominent civil rights activist Nannie Helen Burroughs, was recently lifted 102 feet back to the surface. Weighing as much as six 747 airplanes and running more than a football field long, Nannie moved at a snail’s pace of 50 to 100 feet per day, ultimately digging a 26-foot-wide, two-and-a-half-mile-long hole underneath Washington, D.C.

Part of the Clean Rivers Project, the tunnel will catch stormwater and sewer overflow in an effort to keep the runoff out of the Anacostia River. It is actually the second of five planned tunnels to be completed. The first tunnel was dug by a machine named “Lady Bird,” which finished its work in the summer of 2015.