The Iowa Beef Processors (IBP) Waste Pond was originally constructed in 1971 and was used for the storage of wastewater from the IBP Beef Processing Plant near Wallula, about 12 miles southeast of Pasco, Washington. When full, the waste pond had a surface area of 37 acres and stored about 270 acre-feet. The pond was created by construction of a 15-foot high, 1000-foot long earthfill dam across a natural ephemeral drainage course. The dam was not provided with any spillways, and thus could not pass any flood runoff from the 55 square mile drainage basin above the dam.
The dam was inspected under the U.S. Army Corps of Engineers Phase 1 inspection program in 1981, and their report concluded that not only was a spillway needed, but that the dam was riddled with animal burrows. In 1985, IBP hired a consultant to perform a geotechnical evaluation of the dam, and they also cautioned that the animal burrows in the embankment were a serious problem and stated that they could initiate a piping failure if left untreated. Despite these warnings, IBP took no action to repair the dam or provide a spillway.
The failure occurred early in the morning of January 25th, 1993. The exact time is not known, but at 3:40 am on the 25th, a Union Pacific freight train derailed on a washed-out section of track downstream from the IBP dam. The breached dam section had a width of 60 feet and depth of 19 feet below the dam crest. The resulting dam breach flood passed down the natural drainage channel below the dam and washout out two additional ponds before overtopping the railroad embankment about one mile downstream. At the site of the derailment, five locomotives went off the tracks and into the flood waters, injuring 3 crewmen.
The estimated cost of this failure was $5 million, which included the cost of damage to the locomotives, environmental cleanup, and repair of the rail line. The cost for IBP to construct a new waste storage facility was several million more dollars. This case study will present the inherent design flaws of the dam, the likely main causes of the failure, and the lessons learned from this event.
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