Preliminary design of the world’s longest sunken tube tunnel is to begin following a recent contract award covering the roughly 30-km Hong Kong-Zhuhai-Macao fixed highway sea link, China. At 5.6-km, the tunnel will be some 2-km longer than the current record holder, on the Denmark-Sweden Øresund crossing, according to the Scandinavian tunnel’s designer, Copenhagen-based Cowi A.S.

Cowi is also in the design consortium just hired by the Chinese government, which includes the Hong Kong office of Arup Group, Chinese Highway Plan and Design Institute Ltd. and Shanghai Tunnel and Design Institute. The link will be elevated for 22.8-km and include three cable-stay bridges, with spans up to 460-m. The estimated $8.5 billion project is due for completion in 2015, with construction starting late this year or early next.