Today, an almost-forgotten catastrophe. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
Kermit Pattison tells about
the day the St. Francis Dam burst. In 1928, this
dam on the San Fransisquito Creek north of Los
Angeles burst, and it killed over 500 people. The
St. Francis dam was the last of William
Mullholland's efforts to bring water into Los
Angeles.
Mulholland, Los Angeles's tough water
superintendent, had built the great aqueduct from
the Owens Valley agricultural region down into Los
Angeles. With water the city grew, and as it grew
it demanded more water. Owens Valley ranchers
finally fought back.
They damaged Mulholland's aqueduct, took over
pumping stations, and kidnapped city officials. Los
Angeles would need a reservoir to sustain its water
supply, so Mulholland chose the San Fransisquito
Creek. He'd built many dams in his work. Now this
dam would create a reservoir of thirty-thousand
acre feet and a year's supply of water.
By now Mulholland's reputation as an engineer was
too strong. As the dam went up, certain features
weren't checked aggressively enough. This was a
gravity-arch dam: heavy enough that the water
wouldn't push it aside, but it also arched back
into the reservoir where its curvature lent it
extra strength.
As work began in 1924, a drought sent people
clamoring for even more reservoir capacity.
Mulholland raised the dam from 175 to 195 feet
without demanding reinforcement. The reservoir
began filling in 1926. Water rose to 165 feet in
the first three months.
A year later, with water three feet from the top,
cracks appeared. Mulholland deemed them the normal
result of concrete curing. When leaks appeared,
Mulholland pointed out that all dams leak. Then, on
March 12, 1928, a strange thing happened. The water
level had been standing just three inches from the
top for some time. In the early evening, the
water-level gage in the center suddenly dropped 3.6
inches. For that to happen, a million cubic feet
would have to've been released. It made no sense.
Just before midnight, a chunk broke out of the east
side of the dam. The center section moved just
enough to break away from the west side, which then
swept downstream followed by twelve billion
gallons of water. No one who watched the dam
burst open lived to tell of it. It was one the
great engineering disasters of all time.
Dawn found Mulholland walking on the mud in the
shadow of the still-standing center section. It
seems he'd built part of the dam on silt without
realizing it. The water level hadn't dropped 3.6
inches before the dam broke. Rather, mud had worked
in below the center and buoyed that section upward,
breaking the sides loose.
The tough Mulholland broke down and wept at the
hearing. He took full blame. He lived only seven
more years with his nightmare. History has debated
his guilt ever since. One thing is clear: The
failure owed much to his own expertise. The dam
broke because people had trouble questioning his
ability. And that's a position that no good
engineer should ever want.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
