The farmer and mechanic. [volume] (Raleigh, N.C.) 18??-19??, 1911-05-30

world, and also because OF the great
controversy that was waged for so
long as TO whether or not II would be
stable. The dam is half q mile wide
and a mile and a half long. 1t closes
up the Chagres Valley, one end rest
ing on a small mountain west of the
ChasTes River. and the other end
abutting on the east side OF the Il
abutting on the locks at the east side
OF the valley. About midway across
the valley there is a minor ridge run
ming parallel with the hills which wall
the lowland. This has been christened
"Spillway Hill by the engineers. and
on its crest is located the spillway
which Will carry all surplus water
from Gatun Lake to the sea.
The Gatun Dam will not be as high
as was originally planned Two years
ago the world was startled by a report
sent out by a Panamanian yellow
Journalist that the Gatun Dam had
given way, although there was no dam
there to give way. This report so
stirred the country hat President
Roosevelt sent a commission of the
hbest engineers in America to visit the
sthmu and the work With
the utmost thOroughness- The net
result was a unanimous verdict that
Gatun Dam was being built useleSsly
big and that unless precautions were
being taken. The commission recon-
mended that the dam be cut down
from 135 feet height to lis feet, and
that the ~interlocking steel sheet piling
which it had been intended 10 drive
into the foundation of the dam be
omitted as an unnecessary p~recaution.
The result is that today the Gatun
Dam is a mile and a half. long, 10
feet high, half a mile thick at the
base. four hundred feet thick at the
water line. and a hundred feet thick
at the top. The water in the Lake
will have a normal level of eighty
five feet, so hat the top Of the dam
will be thirty feet above the ordinary
axe eVel.
The average conception of the Ga
tun Dam as a high wall of mud, or as
an artificial mountain with preclpi-
tous sides is entirely erroneous Its
slope is so gradual that it is hardly
noticed in the landscape. Take a yard
stick and raise one end three inches
higher than the other, and the result
ing slope viii, be considerably greater
| than the average of that OF Gatun
Dam. Its slope is less than one-third
Of that of many Of the
hills.
The work of constructing the Gatun
Dam is proceeding with wonderful dl-
spatch. 1t will contain twenty mil
| lion cubic wards of material, and con-
siderably more than half of that
amount already is in position. During
the fiscal year of 1910, more thar tive
| HlllIOIl N6iOS ol IIdlCi "C1S pAoN1N
in the dam. Construction was begun
by building two lines of stone retain
ing walls across the valley, Loo feet
apart. Between these two walls, which
are known technically as the toes Of
the dam. millions of cubic yards of
sand and clay are being pumped to
make the core Of the dam. This is
being done by huge, twenty-lnch CEN
trifugal pumping dredges. AS the
dam rises from its foundations a large
pond will be maintained on its crest
into which the materials will be pump
ed The water will run off and the
material it contains will remain on
the dam.
y In this way the engineers have a per-
petual guarantee that the dam they
are building is water-tight and safe.
/ With vast quantities of water on top
of the dam it is plain that if there
are any assures or other weak spots
the water will seek them out and
show them up. Here again the wis
dom Of the engineers has been Vindi-
cated-the material is more imper-
vious to water than they promised it
should be. IT becomes almost as hard
as concrete and forms a core that
water cannot get through. The natur-
al cement held in suspension by the
dredged water tightens up every tiny
space as a brick mason might close
a hole in a wall. One end of Gatun
Dam is now considerabl bly, higher than
half its final height and the other end
is almost to the halfway point.
The engineering problem of Gatun
Dam has been solved. The part of
the work which still demands the at
tention of the engineers is the Gatun
SpillWay. The Chagres River is a
moody old stream. To-Day it will be
as gentle as a dove, so shallow and
quiet that q boy of ten could wade
across it; While tomorrow it may be-
come a torrential river with a sustain
ed flow of $4,000 cubic feet a second.
How to build a spillWay that viii pass
such an enormous amount Of water
down from an eighty-five foot level to
Sea-leVel without harming any detail
Of the works was a problem which
called for the highest engineering
skill. It is true that Gatun Lake is so
big that the Chagres could flow into