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The Day the Dam Burst
"even when dry, was o.f deci~edly inferior
UNIQUE strength and . . . when wet, beoame so so.ft
that most o.f it lost almost all rock character-
istics." The probers concluded that "the
ultimate failure of this dam was inevitable,
unless water could have been kept from
reaching the foundation."
Instead, they found, water had percolated
into and through the area where the schist
and conglomerate met, "with resulting soft-
ening of the conglomerate under the dam."
No eyewitness of the actual break, if
there was any, lived to tell what he saw,
but Gov. Youf1g's investigators were certain
that they knew what had happened:
"Either a blowout under, or a settling
' of the concrete at, this place, or both, oc-
curred, quickly followed by the collapse
of large s:ections of the dam."
The commission had one conclusion of
overriding importance: "The failure of this
dam indicates the desirability of -having
all such sb·uctures erected and maintained
A perfect seedbed under the supervision and control of state
authorities."
The next session of the legislature wrote
in one easy the decision into California law. Never
operation-yours again would one individual be the final
authority on the safety of any dam of im-
portance. This legal attitude became uni-
only from GRAVELY versal in the United States.
In addition, engineering geologists are
Easy! Frnish plowing, start planting. now on every major dam-building staff, and
Powerful 4-blade Rotary Plow pulverizes practical geology is part of every . civil
soil, leaves it ready for planting. engineer's college curriculum.
And after your garden's in, power cul- "If the St. Francis Dam were to be re-
tivate all season long with Gravely's built today," a California engineer told me,
"it would probably be an embankment dam,
Rotary Cultivator ... aerates soil thor- not a gravity dam. That would spread the
roughly, completely. Both among 31 base over a much greater area and very
year-round -use attach- much lighten the unit load on the founda-
ments for the all-gear tion. Putting a gravity dam there was
drive Gravely Tractor . .. rather like resting a woman's full weight
now available with on a spike heel."
Free booklet · ·· standard 4·-speed or new Bet d1e St. Francis Dam has never been
"Swiftamatic" 8-speed rebuilt, though Power Plant No. 2 rose
transmission. again just where it first stood.
San Francisquito Canyon is silent as a
Check the Yellow cemetery at the old dam site today. Ap-
Pages for your nearby propriately so, for it still contains memorials
Gravely dealer ... see to the disaster that occurred there 36 years
him soon. ago. The dry stream bed is littered with
rounded fragments of concrete. Protruding
GRAVELY ends of reinforcing rods, twisted like string,
testify to the terrible strength of the water
that hurled them there on that long-ago
5903 Gravely Lane, Dunbar, W. Va. 25064 night in March. • •
182 POPULAR SCIENCE MARCH 1964