in 1926 engineers and construction
workers congratulated themselves on the
completion of the saint francis dam
little did they know but two years later
the fruit of their labor
would be rubble and over 400 people
would lose their lives
[Music]
dam disasters are intriguing as the vast
structures seem
indestructible as they hold back
mind-blowing quantities of water
however as we have seen many times
before on this channel
engineers can and have got it wrong and
the results can be catastrophic
today we're looking at the saint francis
dam and i'm going to rate it here eight
on a patented plainly difficult disaster
scale saint francis dam was located
in la county california usa which is
around here
on a map our story starts with eventual
superstar engineer
william mull holland starting off from
more humble route in 1878 he was hired
by the los angeles city water company
as a ditch tender proving to be a good
employee mulholland raised through the
ranks eventually reaching superintendent
during his rise to power mulholland had
become a self-taught engineer
studying in his free time being a bit of
a future thinker
mulholland envisioned an aqueduct to
supply los angeles with water
from 233 miles away in the owens valley
plenty to allow the city to grow
taken on as chief engineer he oversaw
the project during his construction
between
1908 and 1913. the successful completion
of the project which at the time was the
largest of its type
brought fame to mulholland's door
although clearly brilliant
mulholland had the ability to improvise
on the spot which is why the aqueduct
was built in a relatively short period
of time
but sometimes this would come at a cost
of shortcuts
he also had an eye for saving money
which is good
for budgets but not good for redundancy
and design
to save money his own staff performed
all their own engineering calculations
without any external review although
frugal
and ultimately okay on the aqueduct when
it comes to dam design and construction
cut corners can cause well we'll find
out later
by the 1920s the demand for water in los
angeles had outstripped mulholland's
aqueduct
reaching a population close to a million
unfortunately the rising population
ran in parallel with a drought in the
region you see the area was subject to
below normal rainfall
two out of every three years as quoted
by mulholland himself
and as such rainfall was very boom or
bust leading to the
idea of creating a large reservoir to
store
brain from the good years to help the
city for the bad
mulholland proposed an ambitious plan to
increase the reservoir capacity
around the city near his aqueducts
terminus the project would involve
modifying existing water works
and constructing seven entirely new dams
the largest of which would be
the saint francis the new dam would
store thirty thousand
acre feet of water roughly the amount
consumed by city residents in 1922.
surveys for the location for the new dam
began in 1922
eventually the site was settled upon and
initial clearing works
began strangely but understandably the
initial building works went on with
little fanfare but this was because
mulholland had been burnt before
during the aqueduct construction
sabotage cost the project money
as disgruntled locals and landowners
sought to cause trouble
by july 1 1924 preliminary clearing
works had been completed
and main construction works would begin
around six weeks later
but first we need to look at the design
of this shiny new to be built dam
the basic design was actually copied
from the mulholland dam built a year
before
by you guessed it mulholland designed by
edgar a bailey
this would be the second dam constructed
of concrete by the los angeles
department of water and power
chief engineer w holbert supervised the
transfer of the design from the
mulholland location to the saint francis
location
the main changes were adjustments to fit
the new setting of the saint francis
area
as such bilmar holland didn't manage the
project on a micro level like he had on
other designs before
this was exasperated by him being
distracted by the concept
of a colorado river aqueduct before the
designs of both dams
the engineering team studied a number of
recent concrete dams
such as the arrow rock dam in idaho and
the elephant butte dam
in new mexico a storage capacity of 32
000 acre feet
and an elevation of 1825 feet above sea
level
was envisioned in 1924 after initial
survey work the height of the dam was
increased by 10 feet
to allow a water capacity of 38 000
acre feet in 1925. the increased size
necessitated the construction of a 588
foot
long dike along the top of the ridge
next to the western abutment
this was not in the original design as
such the foundations were not widened
for the extra height
the design incorporated a curved plan
laid out on a radius of 500 feet
we have a distinctive series of five
foot high vertical steps on a downstream
face of the main dam
each step was unique in its width and
was a simple solution to building a
complex curve but dam didn't have a
provision for groutable contraction
joints however
a concrete batch plant was built in the
canyon of the dam and local aggregate
was incorporated with around one barrel
of portland cement per cubic yard of
concrete when the concrete was poured
little thought was given to contractions
due to heat given off whilst curing
this combined with the oversight for
contraction joints
left the dam inflexible and potentially
unstable
the reservoir that the dam would hold
back began being filled
in march 1926 with water diverted from
the owens river aqueduct
and the completed dam was opened in may
1926
during reservoir filling a number of
small cracks and leaks were detected
but thought to be within expected
tolerances between march and june
the reservoir filled at a rate of about
1.8 feet per day
and on may 10 1927 the reservoir pool
reached an elevation of 1832 feet
just three feet below the spillway crest
summer demand kept a water level
at that elevation during the winter
months between 1927 and 1928 the
reservoir was allowed to fill up to
just three inches below the spillway
by around february all of la's
reservoirs were beginning to fill up and
on the 7th of march
aqueduct water was no longer diverted to
the reservoir
dam keeper tony harnishvega alerted the
company on the morning of the 12th to
dirty water cascading down the slope
below the dam's right abutment
the presence of dirty water can give an
indication of foundation erosion
because the reservoir was at maximum
fill and new cracks in the concrete were
discovered over the previous week
mulholland and harvey van norman arrived
to investigate the dirty water
and the dam as a whole arriving at 11am
the two men began to investigate the
instability of the structure
because the dirty water was seen to be
clear water mixing with loose dirt from
a newly constructed road
although alarming it was seen as a
problem that could be rectified later on
the rest of the structure was inspected
and given a seal of approval
well how wrong they would be just 12
hours later
around 8 pm employees from one of the
nearby powerhouses
witnessed a 12 inch wide crack on a
nearby road
upstream from the dam hinting towards
the land
around the dam beginning to shift ace
hopewell
powerhouse number one's carpenter was
riding his motorcycle along the road
nearby
passing the crest of the dam around 11
50 pm
he pulled up his bike inside car around
a mile up from the dam
to have a cigarette and to investigate a
loud crashing sound
the southern california edison company
experienced a loss of power at 11
57 pm on their 70 kilovolt boral power
line that ran near the dam's left
abutment
extending eastwards to palmdale the
shorting out the power line hints at
large-scale
landslide that enveloped the dam's
entire left abutment
starting after disaster in the closing
minutes of the 12th
and the opening of the 13th of march
1928
the dam experienced a catastrophic
failure within minutes the majority of
the dam had disappeared
leaving only a central section standing
like an island
the flow of water was monumentous
forming a hundred and forty feet
high flood wave washing away large chunk
of the wrecked dam
as 12.4 billion gallons of water surged
down
the wave traveling at around 18 miles
per hour
destroyed powerhouse number two drowning
nearly all the workers and their
families who live nearby
the flood water overflowed the santa
clarita river's banks
flooding present-day valencia and
newhall
by 1am the entire santa clarita valley
was plunged into darkness
a temporary construction camp set up by
edison company
was washed away killing at least 84. the
flood damaged the towns of fillmore
bardsdale and santa paula eventually
emptying bodies and debris
into the pacific ocean 54 miles
downstream
the flood water was thought to have
killed at least 431 people
although this number doesn't count
migrant workers casual labourers and
illegal immigrants
all of whom would have had no record of
being in the region
many dead were never found or identified
including dam keeper tony harness vega
although his wife's body was found near
the dam suggesting
that a late night inspection was being
undertaken potentially due to the
landslide sounds heard by ace hopewell
so how did such an impressive structure
fail so catastrophically
there was and there still is differing
theories on the failure
it is thought that a failure started
with the left east abutment suffering a
landslide
the left fell side was then swept in
front of the dam
leaving debris as evidence of the likely
side of first failure
a committee appointed by the los angeles
city council set about working on an
official report into the failure
the key failure was placed at defective
foundations and the report essentially
said the dam was well designed but
poorly executed
with an error in judgment about the
suitability of the area's geology
as a stable foundation for the dam the
investigation though
claimed it was the right western
abutment that had failed first
owing to cracks discovered leading up to
disaster but more modern analysis
have speculated differently two
alternate reports by bailey willis
and karl e grunsky support left eastern
side failure theory
they also focused into a phenomenon
called hydrostatic
uplift this is where water seeps under a
dam
and causes an upward force on the dam
reducing its effective weight
although known at the time the
phenomenon was not properly understood
and saint francis dam didn't take this
into account
meaning that hydrostatic uplift mixed
with an unstable land from historic
landslips
caused the failure at saint francis
the dam was not rebuilt and for a short
while became a morbid attraction for
locals to come and collect souvenirs
as the single standing part remaining
known as the tombstone
the site would be cleared and the
tombstone demolished in mid-1929 to
detract a strange
tourism to the area because my holland
dam was essentially identical
330 000 cubic yards was
used to reinforce it from the risk of
hydrostatic uplift
the hollywood reservoir that mulholland
holds up was not allowed to exceed
4 000 acre feet of water mulholland's
career
also ended on the night of the 12th and
the 13th of march 1928.
during the inquest he claimed full
responsibility and retired
in november the same year no criminal
charges were brought against the
designers
with the inquest finding no evidence of
criminal act or intent
mulholland would die in 1935 at the age
of 79. thanks for watching i hope you
enjoyed the video
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