Reclamation Information Sharing Environment (RISE)

Penstock structures on Reclamation dams provide regulated flow to powerplants and outlet channels using gates or valves on their downstream end. Guard gates, typically located on the upstream end of the penstock, are an important feature for filling, dewatering, and other operations. They also provide a measure of redundancy for isolating or shutting down equipment in emergency situations when the primary shutdown equipment is disabled. An important feature during emergency shutdowns is the air vent system that prevents extreme negative pressures in the penstock. This report concatenates four case studies that assess air vent sizing at Reclamation facilities during unbalanced guard gate closures. This report also presents guidance that can be used for assessing similar facilities.