The sun. [volume] (New York [N.Y.]) 1833-1916, 1915-06-06
NEW

REAT interest was excited
among engineers a year ago
~ by the announcement that in
constructing the new 1850
foot piers between Forty-fourth and
Forty-sixth streets the Dock Depart
ment planned TO hold the Hudson
River at bay for a shore length Of
nearly 500 feet by means Of a dam
Of exceptional size. The project has
now been, carried out. The cofferdam
has been built INT the enclosed basin
has been drained Of its 5000, 900 gall
Ions Of water. The structure Is unique
in its effectiveness, as well as in its
dimensions. for II Is fulfilling its mis-
sion with a measure Of thoroughness
not before accomplished in any SINH
lar undertaking.
The piers to be built now include
the whole Of the first and one-half
OF the second OF the 1850 foot group
Of piers that will form berthing
spaces for the biggest Of transatlantic
liners. 1t was found when the river
ward limits were fixed by the United
States army engineers that for the
slips enough water could be obtained
near the shore only by extensive eX-
cavating Of underlying rock.
Experience had proved work Of this
sort to be extremely costly and at
best it meant that jagged surfaces
would be left projecting upward. With
ocean liners costing millions Of dol
lars n so heavy that their least con
tact with rocky projections would rip
their steel skins Dock Commissioner
Smith wisely decided to eliminate that
peril and at the same lime to cheaper
the cost Of the quarrying operations.
Accordingly. after careful study Of
what wa done by the United States
Government in the case OF the ~refoat-
ing Of the wreck Of the old battleship
Maine and the Black Rock harbor
Improvement in the Niagara River
Engineer Charles w. Stamford OF the
Dock Department decided TO have re-
course to a steel spined cofferdam
patterned after the examples set by
the Government undertakings. But
even Sc he had to contend with a far
more serious problem than that pre-
sented at Havana or at Black Rock.
In the case Of the Maine the hulk
was surrounded by an elliptical Golfer
dam made up Of a series Of circular
units Of steel sheet pilings with their
cavities loaded with mud. The very
form Of this enveloping wall made
it possible TO shore the various ele-
ments by heavy beams canted against
them from within he space to be
drained n also at certain points
to tie the conerdam units by braces
spanning the minor axis of the ellipse
from side to side. With all OF these
precautions II was found necessary
rn1tnnnx, % .n4ltf,, A.. I..ir. "a A.
cofferdam during its building, entail
ing a total outlay OF $7S5,i74 instead
OF the original estimate Of $500 900.
In the case of the Black Rock cof-
ferdam the constructors had to con-
tend with water Of moderate depth,
while at Havana the bottom lay
thirty-seven feet below the surface
Of the water. In New York the task
was to provide against a head Of
sixty-eight feet and the enormous
hydrostatic pressure that would be
exerted against the bulkhead by the
river when the supporting water
within the enclosure was withdrawn.
1t was necessary not only to old the
river at bay above the Hudson's bed
but also to arrest leakage through the
underlying silt and sand.
At the Black Rock harbor site
three fifteen inch pumps were kept
continually going in order to neu-
tralize the leakage. and at Havana
ceaseless pumping was also required
to prevent the water from flooding the
enclosed area after Its draining. To-
day the New York cofferdam space Is
dry; the leakage Is substantially
nothing.
The achievement was not due ia
chance; 1t was the result of careful
planning. Engineer Stamford could
not count upon the self-supportins
factor OF an eliiptical cofrerdam. He
had to provide for substantially a
straight bulwark against IN Hudson
and, with water nearly twice as deer
as that at Havana, he had to make
sure that his work should be strong