Both the tank and flushing chamber are empty. In dry weather situation the gate hangs loose on the frame and stays open.
During a storm, the level in the storm tank / sewer will rise and the gate will be closed following a signal from the float switch. The hydraulic pump starts and drives the shaft, which in turn closes the gate. As soon as the gate is closed it is locked mechanically the hydraulic pump shuts off. The flushing chamber fills as the level rises within the tank / sewer.
The storm subsides and the storage chamber empties leaving sludge and other sewage related debris on the chamber floor.
Once the tank is empty the flushing sequence starts automatically. The float switch sends a signal to the control panel. The solenoid valve then turns the hydraulic pump on. The drive shaft reverses and release the retaining lock hooks. The gate swings open due to the pressure of the head in the flushing chamber releasing the flush water and cleaning all the solids from the floor of the tank or sewer.