The St. Francis Dam Disaster
March 12-13, 1928.
Located 40 mi. north of Los Angeles, Calif.

The Loss: 450 known deaths. 700 homes destroyed. The dam had cost $1,300,000 and there were claim damages of $30 million.

The Cause: The dam, completed in May, 1926, rested on a foundation imbedded 30' in the earth. It was 175' thick at its base and tapered upward 175' above the stream bed. Had geologists been consulted, the damsite across San Francisquito Canyon would not have been chosen. But design engineers could see no problems arising from the anchoring of one side of the dam in unstable laminated rock, and the other side in rock composed of gravel and pebbles. In between these anchorage points the dam sat not upon bedrock, but upon compressed powdered rock, a substance semisoluble in water. Though built to the highest standards of the day, the dam actually relied on its sheer weight to withstand the elements and the pressures of impounded waters. In less than 2 years from its completion it collapsed.


St. Francis Dam after completion

The St. Francis Dam was a concrete gravity-arch dam, designed to create a reservoir as part of the Los Angeles Aqueduct. The dam was located 40 miles northeast of Los Angeles, California, near the city of Santa Clarita. The dam was built between 1924 and 1926 under the supervision of William Mulholland, chief engineer and general manager of the Los Angeles Department of Water and Power (then called the Bureau of Water Works and Supply). Three minutes before midnight on March 12, 1928, the dam catastrophically failed, and the resulting flood killed more than 600 people. The collapse of the St. Francis Dam is the worst civil engineering failure of the 20th century and remains the second-greatest loss of life in California's history, after the 1906 San Francisco Earthquake and fire, and marked the end of Mulholland's career.

Throughout 1926 and 1927, several cracks appeared in the dam and its abutments, some of which leaked muddy water as the reservoir was filled. The cracks and leaks were inspected by Mulholland, who dismissed them as normal for a concrete dam the size of the St. Francis. On March 7, 1928, the reservoir was filled to capacity for the first time, whereupon damkeeper Tony Harnischfeger spotted new cracks and leaks and contacted Mulholland, who again dismissed them as normal.

The same week, motorists traveling on the road along the east shore of the reservoir reported cracks, then a deepening sag in the roadbed near the dam's east abutment. By the morning of March 12th, the roadbed had sagged almost five feet.

The same morning of March 12, Harnischfeger discovered a new leak and immediately alerted Mulholland. Mulholland and his assistant Harvey van Norman inspected the new cracks and leaks, and once again Mulholland, convinced the leaks were relatively minor and normal for a concrete dam, pronounced the dam safe.

Three minutes before midnight on March 12, 1928, the St. Francis Dam catastrophically failed, less than 12 hours after Mulholland had inspected and declared it safe. There were no eyewitnesses to the dam's collapse, but a motorcyclist named Ace Hopewell rode past the dam and reported feeling a rumbling and the sound of "crashing, falling blocks," after riding about a half-mile (800 m) upstream. He assumed these were either an earthquake or another one of the landslides common to the area, not realizing he was the last person to have seen the St. Francis Dam intact, and survive.

Damkeeper Tony Harnischfeger and his family were probably the first to die in the floodwave, which was at least 125 feet (38 meters) high when it hit their cottage in the San Francisquito Canyon 1/4 mile downstream from the dam. 45 minutes before the collapse, the motorcyclist also reported seeing a light in the canyon below the dam--the dam itself did not have lights--suggesting Harnischfeger may have been inspecting the dam immediately prior to its failure. The body of Harnischfeger's wife was found fully clothed and wedged between two blocks of concrete near the broken base of the dam; their six-year-old son's body was found further downstream, but Tony Harnischfeger's body was never found.

Twelve billion U.S. gallons (45 000 000 000 liters) of water surged down San Francisquito Canyon in a floodwave, demolishing the heavy concrete walls of Power Station Number Two (a hydroelectric power plant), and destroying everything else in its path. The flood travelled south down San Francisquito Canyon, flooding part of present-day Valencia and Newhall. The deluge then turned west into the Santa Clara River bed, flooding the towns of Castaic Junction, Fillmore, Bardsdale. The flood continued through Santa Paula in Ventura County, emptying its victims and debris into the Pacific Ocean at Montalvo, 54 miles from the reservoir and dam site. When it reached the ocean at 5:30am, the flood was almost two miles wide, traveling at a speed of 5 miles per hour. Bodies of victims were recovered from the ocean, some as far south as the Mexican border.

Telephone operators in Fillmore (notably Louise Gipe) and two motorcycle policemen in Santa Paula notified people in their homes of the danger, until the rising floodwaters forced their retreat.

The dam broke into several large pieces, some of which were carried almost 1/2 mile downstream, while the center section of the dam--nicknamed "The Tombstone"--remained standing.

St. Francis Dam after the breach

The exact number of victims remains unknown. The official death toll in August 1928 was 385, but the bodies of victims continued to be discovered every few years until the mid-1950s. Many victims were swept out to sea when the flood reached the Pacific Ocean and were not discovered until they washed ashore, some as far south as the Mexican border. The remains of another victim were found deep underground near Newhall in 1992, and the current death toll is estimated to be more than 600 victims (excluding the itinerant farm workers camped in San Francisquito Canyon, the exact number of which will never be known.)

The Los Angeles Coroner's Inquest concluded the disaster was primarily caused by the paleomegalandslide on which the eastern abutment of the dam was built, but would have been impossible for the geologists of the 1920s to detect. Indeed, two of the world's leading geologists at the time, John C. Branner of Stanford University and Carl E. Grunsky, had found no fault with the San Francisquito rock. Therefore, the jury determined responsibility for the disaster lay with the governmental organizations which oversaw the dam's construction and the dam's designer and engineer, William Mulholland, but cleared Mulholland of any charges, since neither he nor anyone at the time could have known of the instability of the rock formations on which the dam was built. The hearings also recommended, "the construction and operation of a great dam should never be left to the sole judgment of one man, no matter how eminent."

Soon after the inquest, Mulholland retired from the LADWP and retreated into a life of self-imposed isolation. He died in 1935, at the age of 79.

Today, the only visible remains of the St. Francis Dam are weathered, broken chunks of gray concrete and the rusted remnants of the handrails that lined the top of the dam and the wing dyke. View a wikimedia map here

[Source: Various sources including Wikipedia.org]

A List of Victims is located at the Ventura County Genealogical Society here

©2006 K. Torp
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