Damn Dam

Dam failures are bad. Really bad. Really really bad. As a society, we depend on our engineers to do the dirty work for us so we don’t have to think about all the hazards around us. And believe you me, there are plenty of hazards to worry about.

The class I teach has been talking a lot about the St. Francis dam lately. It was a dam built in the 20s by our friend William Mulholland. Two years after its completion, the dam failed and sent a wall of water roaring thru Santa Clarita and on out to the Pacific Ocean. It is the 2nd greatest loss of life in California, the 1st being the 1906 San Francisco earthquake. The tragedy killed at least 600 people (which is not insignificant considering the population of the area at the time) and ruined the career of our buddy Billy M.

After completing his first engineering masterpiece, the LA Aqueduct, Mulholland set his sights on water storage rather than water transport. He wanted to construct a reservoir of fresh water that LA could tap into incase something happened with the Aqueduct system. After the 1906 earthquake, geologists traced the San Andreas down to the vicinity of LA and Mulholland knew that his aqueduct snaked over the fault a couple times. It didn’t help that farmers were sabotaging the LA Aqueduct because of the royal screwing over they had received when water was diverted from the Owens Valley. He took all these factors into consideration and decided that it would be best to have a reservoir that could meet LA’s water needs for as long as necessary to get the water flowing again. A reservoir would need a dam.Above is a colorized picture of the St. Francis dam as it was. It's ok for that water to be comming out the middle. That part of the dam is called a spillway and allows water to be released from the reservoir when necessary. The 200ft gravity dam was completed in 1926 and promptly filled with water from the Aqueduct system. Everybody was happy, especially ole’ Mulholland.

The dam was leaky to begin with. Throughout 1926 and 1927, the damkeepers were forever noticing little spots of water seeping through the concrete. Mulholland justified these leaks by saying “Poppycock! (or whatever other 1920’s guffaw you can think of) That’s only natural. The concrete is settling as the reservoir is filling behind it, no big deal”.

Early in 1928, lots of people began tapping Mulholland on the shoulder saying “Ummm, there’s a lot of water leaking through your dam. Are you sure we shouldn’ be worried?” Under the advisement of the damkeeper, Tony Harnischfeger, Mulholland marched up to the dam for a personal inspection during the daylight hours of March 12, 1928. He walked on it, tapped it, probably kicked it a couple times, perhaps jumped up and down on it, and declared it safe. End of story. Stop calling me Harnischfeger he probably thought. What a pussy-ass damkeeper I’ve hired.
Even though it’s a confusing name, we should remember Tony Harnischfeger for being of sound mind. He was right to be worried because at 11:57pm that very same night, the dam busted wide open. A volume of water equal to three times the flow of the Mississippi roared down the canyon. It obliterated everything in its path. The map above shows the path the flood took. It followed along the Santa Clara River (see below) all the way to the ocean. Bodies were found as far south as San Diego and even Tijuana.


The cause of the break was not shotty engineering, but unsound geology. One side of the dam was built on an old landslide. The rocks on that side are schistose – schist being a metamorphic rock that has well defined layers. Under a sufficent load and with proper lubrication, this stuff sloughs off along the planes of the layering. The other side of the dam was built on a rock that disintegrates when wet. It seems solid enough when it’s dry, but saturate it with water and what was sturdy rock crumbles to pieces.

This catastrophe left Mulholland a broken man. To his credit, he did take full responsibility for the dam failure. Subsequent trials and investigations acquitted him of any egregious wrong-doing. What WAS his fault was the poo-pooing of any advice given to him by geologists before building his dam. He died in 1935 at the age of 79.

So there you have it. The story of St. Francis dam. Heavy shit, huh? I'll spare you the "those who do not learn from the past are doomed to repeat it" banter. It's an incredibly interesting story and one that all Angelinos especially should know.

Citations:
* St. Francis Dam - J. David Rodgers and Kevin James. Department of Geological Engineering. University of Missouri - Rolla
* Santa Clara River - Matthew Trump