 Days after the first filling of the reservoir , around 80 hairline cracks were observed in the dam 's structure . The submerged spillway gates of the dam might pose a risk of cavitation , similar to that which severely damaged the poorly designed and <unk> spillways of the Glen Canyon Dam in the US state of Arizona , which was unable to properly withstand the Colorado river floods of 1983 . However 163 @,@ 000 concrete units of the Three Gorges dam all passed quality testing and the deformation was within design limits . An experts group gave the project overall a good quality rating . 
