The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1885-1921, 1892-10-27
The HAkBUk BAR.
Inc Scientific American Publishes
an Article About It.

october Sth:-
IA matter of interest to engineers
anu OF great value TO commerce il the
accomplishment of the work nj Ont
ting a channel 200 feet wide and "a
feet deep through the bar at the en-
trance of the harbor of Honolulu.
Hawaiian Islands.
The harbor is deep, narrow chan
mel, extending from the shore line ont
TO the deep waters of the open sea-a
distance Of about 1000 feet. IL is
hanked on both sides by extensive
mud and sand flats, which are bound
ed on the seward side by line of
coral reefs of irregular depth, upon
which the surf is continually break
ing. The width of the channel direct
~ III front OF the city is from 500 to
so0 feet, gradually contracting to a
Wlutn OF about 40 feet at its mouth.
The bar is situated near the outer end
of the channel, is about 100 feet in
length above the plane of 80 feet depth.
and has on its apex minimum dentb
OF Il feet at low tide. Inside of the bar
the depth of the harbor varies from
Is 10 81 feet. The average rise of or.
binary tides is one and seven-tenths
Ieet; OF spring tides, two feet; and of
neap tides, one and two-tenths feet.
In May, 1890, Mr.. Lorrin A. Thurs
ton, then the very able and progress
sive Minister of the Interior of the
Hawaiian kingdom, commissioned
MIR. q. +. Allardt, an eminent civil
engineer from California, to inyesti-
gate the subject of deepening the
bar. The engineer was to report
Fist, the proper method and plant
necessary to remove the bar; second,
the estimated cost of the same; and
third, the proper method of thereafter
keeping the channel open.'
Mr.. Thurston having shortly after
ward resigned, Mr.. e. n. Spencer, the
present Minister of the Interior, took
up the work with great interest and
has carried it to successful conclu-
sion. After very careful examina-
ton, Mr.. Allardt reported that the
material in the bar, to the depth of so
feet at low tide-ascertained by num-
erous borings made with an ordinary
sand pump worked by hand-consist-
ed of loose coral sand, with a few scat
tering pieces of coral. To secure a
clear and indisputable depth of 80 feet,
he estimated that the amount to be
excavated would ultimately reach co.
600 cubic yards.
The dredging operations of the Uni
ted States Government in San Fran
cisco Bay and Oakland Harbor, where
the material is similar and where the
hydraulic method of pumping it up
and transporting it by water carriage
through sheet iron pipes to the place
of deposit has been very successful,
furnished a basis for estimating the
cost of similar work at Honolulu.
The Hawaiian Government was de-
sirous Oh retaining O tract of about
twenty-eighu ceres of land in the east
ern part of the L. Dor, at an average
distance of $500 feet from the bar.
Taking into account the building of a
levee around this tract, the greater
cost of labor and coal, the increased
expense of shipping the machinery of
the dredger in detached parts from
San Francisco, Mr.. Allardt estimated
the cost of deepening the channel at
S9S,O00. OF this sum S65, 900 was al
lowed for u dredging machine of the
Won Schmidt pattern, $4,000 for cost of
pipe, and the remaining So, 900 for
dredging.
He further suggested that to get the
full benefit of deeper channel across
the bar an equal depth should be
secured in the harbor itself. Accord
ingly, to obtain q uniform depth of 30
feet at low tide over all that portion
of the harbOr comprised within the
line of Is feet depth, it would be
necessary to eXcavate about $4,000
cubic yards of material, which would
be sufficient to reclaim and bring up
to suitable grade about eighty acres
of land now useless for business pur-
poses.
Frequent soundings made on the
bar during the past forty years show
no material change in the depth of
water, proving cOnclusively that dur
ing that period of time no appreciable
movement of material has taken place
either outside or inside of the bar, or
- on the bar ITSELF
The Honolulu bar, like others in
tidal waters, was probably formed by
the action of opposing forces from
within and without. In course of
time these reached an equilibrium
and resulted in the present permanent
condition of the bar. 1t is probable
that as this condition of equilibrium
is disturbed by the artificial deepen
ing of the bar the same forces will
tend to fill it again to the normal
depth. This will be very gradual,
however. The concentrated ebb cur
rent will assist in securing the chan
mel and aid slightly to keep it open.
In accordance with the advice of
Mr.. Allardt, the Hawaiian Govern
ment gave the contract for building
Won Schmidt dredger to the Risdon
Iron Works and San Francisco Bridge
Company, jointly, for $4,000. This
was commenced in July, 1891, and
finished May 80, 1892. 1t consists of
a fiat-bottomed rectangular scow 100
feet long, 40 feet wide and 8 feet deep,
carrying centrifugal pump driven
by a pair of compound condensing
engines of 350-horse power. There are
also pair of engines of 75-horse
power for the cutter gear, and
another pair of 75-horse power
for the winches. All the en-
gines and pumps exhaust into sur
face condenser. Steam is supplied by
a pair of fire box boilers feet in dia-
meter and % feet long. The pump is
guaranteed to raise 10000 cubic yards
of coral sand or $4,000 yards of mud
per month, but its actual capacity is
probably three times that amount.
The contract for dredging was taken,
by the same companies jointly which
built the dredger, at $4,000, sum
hIx, hoxya tho oct innate after