Construction of a tunnel 50 meters beneath a river has revealed an unexpected geological hazard. Engineers discovered the structure is built directly over a fault line. The tunnel currently has only 5.5 meters of material separating it from potential seismic activity. The presence of 430 cubic meters of water above the tunnel adds to the complexity and potential danger. This discovery presents a significant, and previously unknown, risk to the project and potentially surrounding areas. Authorities are likely to reassess the engineering plans and safety protocols in light of this finding.