Teton Dam - Filling The Dam

Filling The Dam

The dam was completed in November 1975, and filling the reservoir began at the standard rate of 1 foot (0.30 m) a day. However, snows were heavy that winter, and five months later the project's construction engineer requested permission to double the filling rate in order to deal with the additional spring run-off, while continuing to inspect for leaks and monitor the groundwater. A month later, even though monitoring showed that groundwater was flowing a thousand times faster than had been originally anticipated, the filling rate was doubled again, to 4 feet (1.2 m) a day.

On June 3 and 4, 1976 three small springs were discovered downstream of the dam, although the water running through the leaks was clear, and such leaks are not unexpected for an earthen dam. At the time, the reservoir was almost at capacity, with a maximum depth of 240 feet (73 m). The only structure that had been initially prepared for releasing water was the emergency outlet works, which could carry just 850 cubic feet per second (24 m3/s). The main outlet works and spillway gates were not yet in service: the gates were cordoned off by steel walls while they were being painted.