St. Petersburg Metro's Frozen Secret: The 1975 Flood That Closed a Tunnel

St. Petersburg Metro Tunnel Flooding: A 1975 Engineering Challenge In 1975, a section of the St. Petersburg metro tunnel experienced severe flooding. Engineers employed an innovative solution: pumping 8,000 tons of liquid nitrogen into the ground to freeze the waterlogged soil. Despite this effort, the flooding persisted, ultimately forcing the closure of the tunnel section. The incident highlights the unforeseen challenges of large-scale infrastructure projects and the lengths to which engineers go to address unexpected problems. The video by PRO МЕТРО offers a compelling visual account of this historical event. "Despite the use of liquid nitrogen, the water kept coming back," explains PRO МЕТРО in the video. This persistent flooding eventually led to the decision to permanently close the affected tunnel section, a testament to the unpredictable nature of subsurface conditions. The story of the 1975 flooding serves as a reminder of the complex engineering challenges involved in constructing and maintaining underground infrastructure. The use of liquid nitrogen represents a unique and ambitious solution, though ultimately unsuccessful in this instance.