What the Bonneville Lock Actually Controls, System by System

The Bonneville Lock is a control system, focusing on sequence and interlock rather than concrete. It maintains four critical parameters simultaneously: water level, chamber depth, upstream pool depth, and vessel position. The upstream pool supplies the pressure source, and the control system determines when to open connections and control the flow rate, using only the head difference between the two pools.

Gate position is achieved through miter gates with leaves meeting at an angle, allowing water pressure to close them without relying on motor power. Vessel position is managed by floating bollards that adjust as water levels rise or fall, keeping mooring lines short and preventing drift or surge loads. The lock's sequence ensures that both ends are never open at once and that gates are never moved against the pressures they were designed for, controlled by a series of interlocks based on valve, gate, and water level positions, as well as vessel presence.

The lock's operation is finely tuned, with failure modes ranging from gate leaks to bollard faults, each of which can lead to significant delays. The lock shares the same river with other control problems, such as the fish ladder, which requires a consistent, predictable flow for fish passage. Power generation also competes for the river's resources, with daily decisions made about how much water to allocate for turbines, navigation, and lock operations.

The layout of the site influences operating logic, determining where lock components are positioned in relation to powerhouses and fish ladders. The key metrics to monitor for the lock's health include water levels at each end, gate and valve positions, fill and drain durations, bollard loads, and the difference between commanded and actual cycle times.

These measurements provide more insight than any inspection report, highlighting the importance of the lock's sequence and interlock system in managing the river's resources effectively.