Engineering Ethics: St. Francis Dam Failure

In Engineering Ethics:The St. Francis Dam Failure , you'll learn ...

• What caused the St. Francis Dam failure
• Warning signs that were overlooked or ignored
• Impacts of the tragedy on the local community and resultant financial settlements
• Lessons learned from the disaster and long-term impacts on the engineering community

Overview

Credit: 2 PDH

Length: 45 pages

The structural failure of the St. Francis Dam is considered by many to be one of the top ten worst engineering disasters of all time and rated the worst overall civil engineering disaster in the state of California. When the dam collapsed, the water that was unleashed created a 2-mile wide, 50-mile long course of devastation that began in the San Francisquito Canyon reaching all the way to the Pacific Ocean at Ventura.

The dam collapse, which occurred on March 12th, 1928, released 15-billion gallons of water in the form of a 140-foot high wave; that wave picked up debris and mud as it travelled down the Santa Clara River Valley at an average speed of 12-mph. The failure of the dam caused the death of at least 450 people and the loss of property estimated at over $20,000,000 (in 1928 dollars).

The construction of the St. Francis Dam was directed by William Mulholland, Superintendent and Chief Engineer for the Los Angeles Department of Water and Supply (aka LA’s Bureau of Water Works and Supply). Mulholland was not formally trained nor educated as an engineer; he can best be described as a “self-taught” engineer.

The St. Francis Dam, which spanned the San Francisquito Canyon approximately 35-miles to the north and west of Los Angeles, was a curved concrete gravity/arch structure that was approximately 210 feet high with a 500-foot radius of curvature and a maximum base width of approximately 140-feet. During the construction phase, the height of the dam was increased approximately 20-feet to increase the amount of retained water; unfortunately, the base width of the dam was not adjusted accordingly.

When the dam was completed in 1926 and the reservoir was being filled (1926 through March 1928), cracks in the concrete structure were immediately observed. Mulholland attributed those cracks to concrete curing. New cracks and subsequent leaks continued to be observed throughout the filling process. However, Mulholland continued to state that the structure of the dam was “sound”.

On the day of the collapse, the dam keeper contacted Mulholland and reported a newly developing larger leak in the structure. On March 12th, 1928 at approximately 12 noon, Mulholland personally inspected the dam and assured the dam keeper that the St. Francis Dam was structurally sound. Approximately 12-hours later, at 11:57 pm, the St. Francis Dam catastrophically failed.

A board of inquiry blamed Mulholland for ignoring signs that the St. Francis Dam was leaking dangerously. Mulholland, who faced criminal prosecution by the LA County District Attorney, finally accepted responsibility for the collapse stating “Don’t blame anyone else. Whatever fault there was on the job, put it on me.” Mulholland was forced to resign in disgrace soon after the incident.