The preliminary design review meeting of Qijia Mountain to Jintang section of the Ningbo-Zhoushan Expressway double track was held in Zhoushan, East China's Zhejiang province, marking a major milestone toward construction of what will be the world's longest undersea six-lane highway tunnel — the Jintang Undersea Tunnel.

The meeting of over 60 experts and representatives from 22 entities included provincial and municipal transportation authorities. Attendees reviewed comprehensive design proposals and conducted on-site inspections of key points. Experts agreed the preliminary designs met feasibility standards and were technically sound, passing the review in principle.

Led by Zhejiang Communications Investment Group, the project involves a total investment of approximately 15.7 billion yuan ($2.18 billion) and is scheduled for completion by 2030.

The 18.1-kilometer expressway — with 5.5 km in Ningbo, Zhejiang, and 12.55 km in Zhoushan — will feature a mainline designed to six-lane expressway standards at 100 km per hour, with the Jintang Undersea Tunnel segment set at 80 km per hour.

Spanning 11.6 km, the Jintang Undersea Tunnel will be constructed using advanced 16-meter diameter shield tunneling technology, overcoming complex geological layers, deep-sea precision docking, and underwater tunnel disassembly challenges — all of which push the boundaries of global engineering.

The project is expected to strengthen the national transportation network, support Zhejiang's high-quality development, accelerate integration within the Yangtze River Delta region and the metropolitan area in Hangzhou Bay, and improve cross-sea transport capacity and emergency response.