Chinese engineers have completed the world’s first tunnel specialized for ultra-high-voltage power transmission lines, designed to cross the Yangtze River in East China’s Jiangsu province.

The tunnel is a key section of the 1,000-kilovolt UHV power transmission project linking Huainan, Nanjing and Shanghai, which aims to help ease power shortages in the Yangtze River Delta region.

The tunnel is 5,468.5 meters long and 12.07 meters in diameter, crossing the Yangtze River from Nantong in the north to Suzhou in the south. The lowest point of the tunnel is 74.83 meters below the water level of Yangtze River.

A specially designed 140-meter shield tunneling machine started excavation work on June 28. The machine was modified to adapt to high water pressure and complex geological conditions on the riverbed.