Flood Control Dam #3

You are standing on the top of the Flood Control Dam #3, which was quite a tourist attraction in times far distant. There are paths to the north, south, and west, and a scramble down.
The sluice gates on the dam are closed. Behind the dam, there can be seen a wide reservoir. Water is pouring over the top of the now abandoned dam.
There is a control panel here, on which a large metal bolt is mounted. Directly above the bolt is a small green plastic bubble.