New Orleans Republican. [volume] (New Orleans, La) 1867-1878, 1875-01-31


vhere it ID .propossato hssinths jetties, tn,
| as it is confined by q slowly widening
channel secured out, the water issuing from
them will, having at first no banks to con
| fine it, spread out more rapidly, thus, per
hape, losing velocity more rapidly and
forming q sleeper seaward slope on the
bottom than now exists at the upper end Of
the proposed dykes. This sleeper slope
| seward from the thirty feet of water be-
tween the jetties would give a sboal OF
twenty five feet at distance of less than
200 feet and in period Of less than twenty.
| two years.
The period is uncertain; experience alone
can determine the precise time. Different
estimates made by this method, and others
by different members of the board, vary
largely, and ten years have been assumed
for the purpose Of estimate. In ten years,
then, it is assumed that the jetties will have
to be heightened 1000 feet. As shoals will
have formed at the ends of the jst'ies, it
has also been assumed that the extension
will be in water averaging fifteen feet in
depth.
1t has been stated that there Is a shOal at
the head of South Pass, with but seventeen
feet of water on the shoals. At present this
shOal is securing out. Should that securing
not give depth as great as at the shoalest
point below the pass, the construction of a
dyke to defect more water into it would
become necessary. Should the South Pass
increase much beyond its present size, it
might become necessary to put an apron on
the bottom and sides Of the pass near it's
head, to stop that increase.
Estimates OF the cost of the ietties ard of
the works which may be needed at the head
Of the pass are given in Appendix 3.
First cost OF jetties at mouth of South
Pass, OF dredging and OF works at
Average annual cost of extension, in ''''D '''
GLIDING removal of mud Jumps
should they rise, $4,000, which,
capitalized at five Per cent, gives. $500 900
Cost Of construction and maintenance of
Improvement. ....................$S 942, ITO
The board also made an estimate Of the
cost of improving the Southwest Pass, the
result Of which is as follows:
First cost Of improving Southwest Pass
Average 'I ANNUAL cost Of extension ~''l'''iA
$3.50, 900. which, capitalized at five
Der cent, ACKNOWLEDGEMENTS. 1900 900
Sum required to improve and maintain
SOulhwest Pass. ...................b16 053 l24
The board has now given plans and esti-
mates for improving the mouth of the Mis-
sissippi, either by a canal or BY opening one
of the natural outlets. 1t is also required to
give its opinion as to which plan ia prefera
BILE. Leaving cost aside for the moment
and assuming that one plan can be az easily
executed and maintained az the other, there
is NO question that the improvement of the
South Pass would be the best that would
give good sea entrance about 900 feet
wide, and a minimum width in the pass of
about $50 feet, while the width of the canal
would be about 300 feet. 1t would offer no
locks taiable to do or suffer iujury) to delay
the passage Of vessels through it. 1t would
give an ample and unobstructed waterway
to commerce in place of q narrow and OBJ.
structed one. Ii the question of coat and
canal $ll,5l4.2Oo, against s7,9i2llO for
the South Pass. The only remain.
ing question is whether the two
plans can be executed and main.
tanned at about the estimated cost
For the canal the difficult points are to
maintain Golfer dam and secure q stable
foundation on which to build the masonry.
BY proper examination it is believed that
sites can be found where Golfer dams can
be maintained, and although the masses of
masonry are heavier than any which have
been built IN that region without settling,
it is believed that by the plan proposed in.
furious settling would be prevented. The
board is there fore Of opinion that the canal |
can be built at the estimated cost. In the
of the South Pass the difficult |
points are the control Of the water entering
It, the removal of the shOal and the main
tenance of channel at its head, and the |
execution and maintenance of that part of the |
ettles living outside of the outer crest of the |
bar. While the proper method of control of |
the water at the head OF the South Pass !
must be learned mainly by trial, great diff.
'ulty Is not anticipated, as such con troll was |
readily obtained on the Sulina. The con.
'tructlon and maintenance of the jetties be-
70nd the crest of the bar is q difficult
work, in which there will be contingencies
arising from the action of heavy storms.
'ither on the ietties themselves or on the
Material on which they rest, and from set
ling. A liberal allowance has been made
or such contingencies and the board
las no reason to increase its estimates.
indeed it is our opinion that experience in
obstruction may very probably show that
he cross section of the dykes NAV be re-.
uced. thus lessening the cost. If the let
les are constructed and maintained, the
nds being prolonged as it becomes neces-
airy, the board has no doubt that the de.
lred depth will be obtained. It therefore
that the South Pass of the
ilsslsslppi river be improved by the plan
lready given.
The board concludes its report with the
that if Congress decides !
open one of the passes Of the river the
ntlre sum necessary to accomplish the
ork be appropriated at once or in some |
'ay he made available. IT the mouth of
le river is to be improved by ietties, the
ork, when once begun, should be pushed
J rapidly as possible to its entire compile
on. The board is of opinion that the works |
proposes for the Improvement of the South /
ass can be completed in three years,
b. S. ALEXANDER.
Lieutenant Colonel of Engineers,
c. b. COMSTOCK,
Major of Engineers. .
HENRY MITCHELL,
United States Coast Survey.
T. Z. SICKLES,
w. minor ROBETS,
II. d. WHITCOMB.
l concur in so much of the report as refers .
the selection of the South Pass for the 8
al OF the Jetty system if that system is to r
adopted. Also, to the plans and esti- =
ates for both canal and jetties. But as .
my judgment the chances of success of :
y one OF the natural outlets of the river
not Justify the recommendation of the h
ard. have withheld my signature from n
report. 1t an adequate and permanent "a
annei could be obtained at any one of the n
sses 1t would no doubt be preferable to y
proposed canal. As the ship canal Dro. .
+ does, in my judgment, offer reasonable !.
ances OF success, l must give it the pref n
nee over the jetty project recommended .
the board. II. s. WRIGHT, II
Lieutenant Colonel of Engineers