One clean piece featuring two simple arches sits atop the banks of a river flowing into an estuary, just about to touch the sea.

It took a complex engineering maneuver to solve a months-long process in just a few hours. A new bridge joins the 14 already over the Nervión River. This is a second link between the island of Zorrozaurre and the city surrounding it, Bilbao, across the Deusto Canal.

The San Ignacio Bridge was installed in April 2020 over the Bilbao estuary; the viaduct consists of a single piece with no expansion joints. Its carbon steel and concrete structure convey lightness, yet it is robust. Its deck, measuring 28 meters wide, is flanked by two symmetrical arches that rise 34 meters at the center. As a whole, the bridge spans 75 meters with no other supports than the banks.

The Deusto Canal, built as a branch of the Nervión when life in Bilbao revolved around its port, is 111 meters wide where the new viaduct crosses it. That distance is shorter, though, after an abutment was built on the island of Zorrozaurre on the canal’s left bank. The abutment, a watertight enclosure made of 24-meter-long sheet piles, makes the bridge fit into the environment in one piece.

By the time the bridge is fully operational, it will have two pedestrian sidewalks on the sides, two lanes for public transportation, and two lanes for other traffic, where cars, motorcycles, and bicycles will share an area with a lower speed limit. For now, though, it will only be used by the trucks working on the construction of developments in Zorrozaurre.