By the end of June, Nigerians will know what caused the June 2 collapse of a four-story building that killed four construction workers in the city of Onitsha, 482 kilometers from the capital, Abuja.The Anglican Church of Nigeria was constructing the building. The church's Niger diocese and the government of Anambra state have set up parallel teams to probe the collapse. Construction experts have blamed several factors, including contractor incompetence and non-compliance to project specifications and standards. The building is suspected to have been initially approved for just two stories. Unconfirmed reports also suggest that, before the collapse, too little
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. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.