The bridge also is environmentally friendly, with special filter screens installed in every drain to prevent rubbish and oil leaked from vehicles from being directly discharged into the sea, Su said.

Yu Lie, deputy director of the Hong Kong-Zhuhai-Macao Bridge Authority, said the number of wild Chinese white dolphins has risen over recent years to more than 1,800.

A total of 258 Chinese white dolphin groups－with 1,890 individual dolphins－were counted in the national conservation zone for Chinese white dolphins at the mouth of the Pearl River, according to a report on the ocean environment off Guangdong province released by the province's Administration of Ocean and Fisheries in 2016.

There were about 1,400 Chinese white dolphins when construction of the bridge began in 2009. Construction of the main structure of the bridge is to be completed soon.

Bridge builders were able to reduce the number of piles driven into the seabed and avoid disturbing millions of additional cubic meters of sand and mud on the seafloor after the designs were further improved to protect the Chinese white dolphins, Yu said.