NIGERIA will begin exploiting its vast deposits of bitumen, an essential material for road construction, next month, an official said on Tuesday. Most Nigerian roads are in deplorable condition due to lack of bitumen, while the oil-rich west African country has an estimated 42 billion barrels worth of bitumen deposits in the southwest of the country. Femi Dada, director of the state-run Bitumen Implementation Project, said work would begin on May 15. He said materials required for large-scale production have also been provided, adding that exploitation would be carried out in phases.