A Massive Safety Feature

Evan now knew what the mysterious vortex was. It was a spillway, explaining why the water surrounding it constantly drained into its dark and deep recesses. The hole was a safety feature designed to keep the Monticello Dam’s integrity by preventing too much water to push against its walls. The continuous draining of the water through its cavernous mouth keeps Lake Berryessa at a constant level that the dam is engineered to hold effectively. But why didn’t people notice it until now?

Hidden in plain sight

The mysterious hole had been hidden in plain sight and the reason was quite simple. In the decade leading to its discovery, Lake Berryessa’s water levels had been critically low thanks to the long California Drought that lasted for 10 years. With its levels at an all-time low, the spillway wasn’t obvious to the plain observer due to the absence of water flowing into it which was what made it appear magical. There was no need for the spillway since the dam was under no threat of being breached by dwindling levels of its reservoir’s contents.