St. Francis Dam Disaster 6

Outland's book and the results of the investigations in 1928 are essential, but the science of geology and the technology of dam construction continue to change. Drawing upon a distinguished panel of historians and engineering authorities, including Duke University professor Henry Petroski, our documentary will take an updated look at the disaster, scientifically, as well as socially and politically. An especially important source for this will be historian and consulting engineer J. David Rogers who has studied the St. Francis story for more than 25 years.

Although it is generally agreed that geological conditions at the site and inadequate construction techniques were major contributing factors to the collapse of the St. Francis Dam, understanding exactly how it happened is a fascinating detective story. We will follow the clues for answers. Just what happened in the surrounding geology that caused the failure? Should Mulholland have known better? Most modern engineers say yes. But evidently, with his years of experience, "the Chief" was confident that he knew best. Clearly, he didn't.

One of the most dramatic pieces of visual evidence from the disaster is the reservoir water level chart, or Stevens Gauge. It drops precipitously at 11:57 AM, a startling indication that the dam was down. But a gradual fall had begun hours beforehand. This would indicate a large outflow of water, but none of the survivors below the dam reported such a pre-flood. What is the Stevens gauge recording? The answer is chilling. In fact, in response to weakening abutment support, the enormous concrete structure was lifting, twisting and tilting, causing the water level to drop against the upstream side of the dam.

And what accounts for the unexpected survival of a single center strip of concrete, and the final resting-places of huge portions of debris, some weighing tons, found far downstream? Investigators beginning as early as 1928, as well as the work of Charles Outland, have helped unravel the mystery. With the help of dramatic photo-realistic 3-D graphics, Rogers presents the results of their work -- and his own -- to provide a complete picture of the collapse and its causes.

Perhaps the most dramatic discovery made during the 1928 investigations was the fact that the St. Francis Dam was built against a series of gigantic prehistoric landslide sites. The terrain that looked so ideal to Mulholland was in fact the result of thousands of years of shifting soil. In 1928 it was this ancient unstable geology that ultimately contributed to the collapse of the St. Francis Dam.

LEGACY

The St. Francis Dam disaster was a major catastrophe for California, but it also had far wider significance. In its aftermath California's first dam safety agency was created, a model for the rest of the nation. On a more personal level, a state-mandated process for the arbitration of wrongful death suits was put in place that has served ever since as another model. Perhaps most importantly, it was acknowledged internationally that outside consultation -- especially geological consultation -- is essential in the design and construction of any dam.

On a broader level the St. Francis Dam Disaster poses serious questions about the writing of history. Why is the greatest American civil engineering failure of the 20th Century so little known? And when it is written about, why are Mexican-American victims and survivors rarely if ever mentioned? Our documentary will address these issues as it places this great national tragedy in its proper place in modern American history.