It is a pipe structure to supply or remove air for smooth flow of water in conduit. Air vent pipes are located between Emergency Gate and Service gates to release trapped air to the atmosphere. If trapped air is not quickly removed to the atmosphere by providing air vent of adequate cross section, it produces additional load on gate parts, causes vibrations to the Dam Structure. Air vent pipes are also provided at downstream side of service gate to supply sufficient amount of air to reduce cavitations. Air vent can be in the form of a steel pipe, a concrete conduct or a dry well with connection to atmosphere at top.