When the heavy rains come as they do every year, the steep mountain slopes on the southern side of Puerto Rico can become deadly. The Portugués and Bucana rivers often overflow with a rapidity that threatens the municipality of Ponce downstream.

The formal completion ceremony for the $386-million Portugués Dam on Feb. 5 marks the end of a long odyssey to solve the flood-control issues that imperil the Caribbean island's second-largest urban area. The 220-foot high structure is the first single-centered, roller compacted concrete (RCC), thick-arch dam, ever attempted by the US Army Corps of Engineers, according to project officials.