On the clear, crisp evening of March...

On the clear, crisp evening of March 12, 1928, a few minutes before midnight, the 2-year-old St. Francis Dam crumpled in the Santa Clarita Valley, unleashing 11.7 billion gallons of water. It was one of California’s worst disasters, with an official death toll--450--just two short of the 1906 San Francisco earthquake and fire.

A wall of water rushed down the narrow gorge of San Francisquito Canyon through Piru, Fillmore, Santa Paula and Ventura before reaching the sea 54 miles and 5 1/2 hours later.

Those who lost their lives included 42 students, half the enrollment at Saugus Elementary School. Some believed that the toll may have been even higher because many bodies, possibly including scores of migrant Mexican farm workers who were never accounted for, were washed into the ocean.

A total of 900 buildings were destroyed and 300 others severely damaged; 24,000 acres of agricultural and home sites were devastated. The cost in 1928 dollars was estimated at $20 million.

Fifteen years earlier, William Mulholland had been hailed as a hero for engineering the 233-mile Los Angeles-Owens River Aqueduct.

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Then came the St. Francis, the 19th dam built under Mulholland’s direction and part of the Los Angeles Aqueduct. When it was completed in May, 1926, few people knew it existed.

Two years later, everyone knew about it.

The morning of March 12, 1928, a Monday, dam tender Tony Harnischfeger summoned Mulholland and his assistant, Harvey van Norman, to tell them about muddy water escaping from the west embankment of the dam. After a two-hour survey, Mulholland declared that repairs were called for but that there was no immediate danger.

Harnischfeger, among others, had expressed his concern about the safety of the dam, basically a giant concrete arch, on a number of occasions. He was so worried that he built stairs to a mountain behind his home as an escape route for his 6-year-old son and himself.

Otto Steen, employed by the Bureau of Water Works and Supply, also saw the muddy water. He later said he and several other employees were “terribly concerned.”

Harnischfeger and his son never had a chance to climb his stairs. They were among the first to die.

As chief engineer of the city’s Bureau of Water Works and Supply, Mulholland considered himself responsible. “Don’t blame anybody else; you just fasten it on me,” he said. “If there is an error of human judgment, I was the human.”

Twelve days after the disaster, a hasty investigation found that his design was at fault. The once-celebrated engineer would spend his last years as a broken man.

The steel-reinforced center portion of the St. Francis Dam survived the break, but the dam was too grim a reminder and was dynamited by the end of 1928.

Mulholland died on July 22, 1935, at age 79. It would take more than half a century for him to be exonerated.

Last year, after an exhaustive investigation, the Assn. of Engineering Geologists’ Southern California Section issued a new study of the disaster.

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“Engineering Geology Practice in Southern California” concluded that the dam collapsed because its eastern edge sat on an ancient landslide that plowed into it “like a bulldozer blade,” causing a chain reaction. Given geological knowledge at the time, the study said, Mulholland and his designers were not aware of the fatal flaw or able to recognize it in the investigation after the collapse.

A book published this summer offers a different explanation. In “Rivers in the Desert,” Margaret Leslie Davis suggests that city officials suppressed evidence of sabotage by ranchers from the Owens Valley, who were angry because--as they saw it--Los Angeles was stealing their water.

Although the disaster cost Mulholland his reputation, his name remains a familiar one to Angelenos. There’s Mulholland Drive and Mulholland Highway, San Fernando Valley’s Mulholland Junior High School and a fountain at the intersection of Los Feliz Boulevard and Riverside Drive, where the engineer lived as a young man. And water still spills daily down the water system that first earned him his reputation and--for a few decades, at least--disgrace.