Decorah public opinion. (Decorah, Winneshiek County [Iowa]) 1895-1928, 1910-03-30

73,000,000 cubic yards of wet or
dredging excavation. One million
yards is contained in a cube 800
feet on each side; the entire amount
would be equivalent to a cube about
a quarter of mile on each side.
1t consists of soft silt, earth, clay
and hard rock The monthly out
put of the dredges at work is about
100000 cubic yards. The great
sea-going suction dredges draw the
material up into bins by centrifugal
pumps, then steam to the dumping
grounds out in the sea, empty by
opening the bottom gates, and re-
turn for another load. They work
night and day, stopping only for
fuel and repairs.
Dry excavation, outside of the
lock construction, is the most
spectacular work on the Isthmus,
and is carried on upon a greater
scale than ever before in the history
of the world. This is done almost
exclusively with great steam SHOW
els, the larger ones lifting five tons
at a time, loading an entire car
with three to four shovels, and a
whole train of cars, carrying 500
tons of dirt, in a few minutes.
The greater part of this work, of
course, is in the big Culebra cut,
about eight miles long and 534 feet
high at the highest point, on Gold
Hill. There are about fifty miles
of railroad tracks in this cut alone,
and over 800 trains, working on
various levels, gradually going
deeper These great steam shovels
load the trains, and they run down
grade east to the Gatun dam and
the Atlantic breakwater. and down
grade west to the Pacific break
water. where they are emptied by
means of a great shovel working
on the principle of a snow plow
from the rear, pulled along the
a powerful windlass at the engine,
which unloads an entire train of
eighteen cars, 500 tons of dirt, and
the train is pulling out again in five
minutes. To prevent the flooding of
the canal prism in the cut during
excavation by water from the ada
cent rivers, the canal channel is
paralleled on each side by diver
siOns" or channels, which turn aside
and carry off the water that other
wise might wash into the cut One
of these alone. the Obispo is 95 feet
deep. so feet wide at the bottom
and 5h miles long. 1t will carry
off 5000 cubic feet of water per
second.
At various points along the banks
of the Culebra cut the excessive
rainfall and the character and slope
of the material results in the move
ment of soft material on layers Of
slippery clay, called Slides" The
best known is the Cucuracha slide,
south of Gold Hill, which has been
a source of annoyance since the
days of the French, in 1884. 1t is
about one-half mile in length and
covers about 27 acres. Over 100000
cubic yards are in motion. 1t moves
as far as IA feet in "a hours, and
has at times filled the entire cut
The only effective remedy for this is
the removal of the dirt, and this is
being done, shelf being construct
ed above the water line some forty
feet in width, and then the cut
sloped backward from there. After
the completion of the work, tropical
vegetation will soon cover this and
prevent it's sliding should it then
have tendency to do so. This has
created considerable comment in the
United States, but has never wor-
ried the canal engineers in the least.
Preparations for the work of ex-
cavation described above are made
by dislodging the rock from the
hill-sides by dynamiting. Hundreds
OF compressed air drills precede the
shovels, there being up to a dozen
in space forty feet wide. These
are supplied with compressed air at
pressure of so pounds from i'm
mense eompressors. and carried in
pipes wherever needed. Holes are
drilled Is to 80 feet deep, to 16
feet apart, and each loaded with 75
to 200 pounds of dynamite, 1,O00,-
600 pounds of which is used month
ly The charges are discharged by
electricity, mainly at night, when
the blasting can be heard for miles.
Rocks which are then too large for
the steam shovels are blasted with
"dobie" blasts, consisting of dyna-
mite placed on the surface, covered
with wet clay, and discharged with
a fuse. One steam shovel has exca-
waited as much as 1000 cubic yards
in eight hours, equivalent to the
work of more than 600 men.
The work requiring the largest