The Wild Story of the Taum Sauk Dam Failure — Practical Engineering

Quick Overview

The Taum Sauk Dam failed on December 14, 2005, due to a series of small oversights, including faulty level sensors, significant embankment settlement, and critically, the absence of a spillway, leading to a catastrophic overtopping and the release of 6 billion liters of water down a mountainside. This disaster prompted major changes in dam safety regulations and design, emphasizing the need for robust, simple safety measures over complex control systems.

Key Points: On December 14, 2005, the Taum Sauk upper reservoir overtopped its parapet wall after pumps continued running despite the water reaching maximum levels, leading to the wall's collapse and a massive surge of water. The primary cause was dislodged and deflected level sensors, which provided readings lower than the actual water level, compounded by operators reprogramming the control system to subtract two feet from the upper set point. The original rockfill embankment had more soil than intended and unsound foundation areas, causing parts of the parapet wall to settle by two feet, making the failsafe probes ineffective as they were installed higher than settled sections and incorrectly programmed. The failure unleashed approximately 6 billion liters of water down the mountainside towards Johnson’s Shut-Ins State Park, sweeping away a park superintendent's family who miraculously survived with injuries and hypothermia. A significant design flaw was the absence of a spillway, as designers never envisioned a need for one, relying instead on complex control systems for safety, which proved insufficient. The Federal Energy Regulatory Commission (FERC) fined the owner, Ameren, $15 million, the largest penalty they had ever issued, and the State of Missouri settled for $177 million, much of which funded park restorations. The dam was rebuilt using roller-compacted concrete, incorporating a spillway, and reopened in 2010, leading to FERC implementing major changes in dam safety oversight, including requiring internal dam safety programs and Chief Dam Safety Engineers.