The call that might have averted disaster came into William Mulholland’s office that morning. Stubborn, single-minded and tireless, lionized and controversial, the Los Angeles water boss was 72. Fifteen years earlier, he had opened the great aqueduct that carried Sierra snowmelt to the San Fernando Valley and made the metropolis possible. Now, on March 12, 1928, a supervisor at the St. Francis Dam was calling to say there might be a problem. Water was seeping from under the structure. It looked muddy, which might indicate real trouble — erosion in the foundation. … “Like all dams, there are little seeps here and there,” Mulholland would later testify at a coroner’s inquest. “Of all the dams I have built and of all the dams I have ever seen, it was the driest dam of its size I ever saw in my life.”