 During the 1980s , the idea of a dam reemerged . The National People 's Congress approved the dam in 1992 : out of 2 @,@ 633 delegates , 1 @,@ 767 voted in favour , 177 voted against , 664 abstained , and 25 members did not vote . Construction started on December 14 , 1994 . The dam was expected to be fully operational in 2009 , but additional projects , such as the underground power plant with six additional generators , delayed full operation until May 2012 . The ship lift was completed in 2015 . The dam had raised the water level in the reservoir to 172 @.@ 5 m ( 566 ft ) above sea level by the end of 2008 and the designed maximum level of 175 m ( 574 ft ) by October 2010 . 
