Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams.
ACS, based in Spain, is one of the most active dam contractors internationally and has constructed 23 arch dams since 1960. Its subsidiary Dragados completed the Portugues Dam, a 67-meter-tall, 275-m-long roller-compacted-concrete thick-arch dam, in Puerto Rico in 2013. And it is nearing completion of the Barro Blanco Dam, in Panama. Barro Blanco is an arch-gravity dam of conventional concrete in the central section and loose materials in the buttresses. It is 55 m tall, with a crest length of 332 m for the concrete section, plus 138 m for the buttresses.