Construction of a $4-billion dam at the heart of Ethiopia’s bid to become Africa’s biggest power exporter has been delayed five years as engineers had to replace shoddy work by a conglomerate pulled off the job last year, a project official said. The Grand Ethiopian Renaissance Dam, announced in 2011, was designed to generate more than 6 000 MW in a region that struggles to produce enough energy, but has proved a lightning rod for tensions in both Ethiopia and Egypt.