The Idaho Republican. [volume] (Blackfoot, Idaho) 1904-1932, 1913-03-14

it was necessary to go through 215
feet of everything earth before COM
ing 20 the rock. The caisson meth
cd had to be restored to, and the cal
son was sunk over 100 feet below
the water line before rock was reach
ed Considerable difficulty was here
experienced in sinking the shaft to
the rock, because it called for the
use OF pneumatic pressure that taxed
the endurance OF the workmen to the
limit. From here on the water will
be conducted through pipes laid in
a trench of moderate depth below
the surface. From the foot of Sew
/ enty-ninth street, Bay Ridge, the
conduit will be run across the Mar
rows to Saten Island, through a pipe
SO inches in diameter, provided with
flexible joints, and laid in>a submar-
inc trench. The details of this sec
ton of the work have not yet been
given out. However tests have been
made to discover at what depth the
pipe line under the water must be
buried. 1t is evident that it must
lie far enough below ground to pre-
vent its being entangled with anchors
from large vessels that may have to
anchor in the Narrows The matter
has been thoroughly Investigated,
and practical tests have been made
BY dragging anchors of large size
along the bottom. 1t has been deter
mined that if the pipe line is buried
at least eight feet under the bed,
it will be entirely safe. On the Stat
en- Island side 4S inch pipe will
carry the water on up the hill and
| through tunnel into Silver Lake
reservoir, 100 miles from the source
in the Catskills.
The greatest interest in this city
| section of the aqueduct attaches ma
turally to that part which is being
excavated through solid rock under
the busy city. 1t is surprising fact
that work of such magnitude can
be carried on directly under our feet
without mountaineering us in the
least. The only surface evidence of
the deep rock tunneling is to be
found at the various shafts which are
located in parks, or public squares.
The principal difficulty that present
ed itself at first was the question Of
storing explosives for a week of such
great proportions To keep the nee
essary explosives on the surface to
harbor constant menaces to the lives
of the citizens. The matter was fin
ally solved by placing the dynamite
magazines far under the surface in
the rock, and setting the doors to
these magazines so they will auto
matically close in case of an explos-
ion and drop the hot and poisonous
fumes in the rock chamber where
they can do no harm to the workmen,
The idea was borrowed from Europ-
can practice, where mining opera
tions are conducted close to and
sometimes directly under large cit
les. Access to the dynamite cham
Der is had through a zig gag drift
At each turn of the drift a pocket is
excavated, and the chamber itself is
made of large capacity. In this
chamber the dynamite is stored I'M
der protecting rock to keep off any
fragments of rocks that might fall
when Jared by the shooting" in the
tunnel. At the entrance of the drift
very substantial concrete bulkhead
is built, and in this is a low door
way. The door is of massive con-
struction, built of I-beams, sixteen
inches deep and spaced apart with
oak beams twelve inches square. The
door has beveled edges, so that it
will seat itself snugly in the door
way The door is always kept open
at an angle of about As degrees. In
the magazine thousand pounds of
dynamite may be kept at a time.
Should this be exploded, the explos-
ion wave would have to travel down
the zigzag passage and would lose
much of its force at each abrupt turn
finally striking the door with great
ly diminished energy. The door
would be slammed shut by the blast
of air issuing from the drift, and
would then be held shut by the gas
es of the exploded dynamite. A mag
azine of this sort has been construct
ed near the foot OF each shaft not at
the foot, however, for fear that in
case of a mishap, it might block
the escape of the men. The magaz-
ines have been tested by exploding
a number of sticks of dynamite
around the first bend in the drift,