China is planning to build a rail tunnel that connects Taiwan to mainland China with Chinese scientists confirming its design, which will be considered to be the world's longest railway tunnel when completed.

"It will be one of the largest and most challenging civil engineering projects in the 21st century," according to a scientist from the Chinese Government who requested anonymity due to the sensitivity of the project.

Chinese scientists are said to be close to a consensus on the design of an underwater tunnel that will connect mainland China and Taiwan. Once completed, this will be the most ambitious and longest railway tunnel in the world that is said to be the 135-km undersea distance at a 250-km/hour speed. The completion of the project is set by 2030.

This project will consume multi-billion Chinese Yuan in engineering and for technical warm-up. Experts said that this will be a major breakthrough for China's science, engineering and construction sectors.

The Chinese Academy of Engineering, which is China's largest central governing advisory board on infrastructural construction, has funded the completion of the underwater tunnel's design. The project has also the full support of China's research corps and construction industry. Several engineering organizations in the country also expressed their support and excitement for the project.

In its design, the tunnel will start from Pingtan, Fujian Province and will go down 200 meters, cutting through large layers of hard granite rocks. It will surface in the coastal city of Hsinchu, near Taipei. The tunnel is said to be three and a half times longer than the Channel Tunnel that connects Great Britain and France. The mainland China-Taiwan underwater tunnel project will have a similar design that of the Channel Tunnel that has three individual tunnels. The two tunnels will be used by trains traversing in opposite directions. In between these tunnels will be a smaller tunnel that will house communication cable wires, power lines, and some emergency exit points.

Some experts, however, cited some challenges that might occur along the implementation and realization of the project. They cited that the political tension between Taiwan and mainland China might hinder the immediate implementation of the project plans. Other analysts, however, were quick to dismiss such challenges and cited that it is possible for the Chinese Government to start the project in a unilateral and very emblematic move.

The mainland China - Taiwan underwater rail project has been an almost century-old idea but it was only in 2016 that it achieved prominence when the Chinese Government included in its 5-Year Plan a high-speed rail network. It was also just recently that the Chinese scientists were able to conceptualize the engineering and design of such a tunnel.