Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-03-04

The obstruction in and about the piers of the
Long bridge make the sections at that point only
approximate. II may be assumed however.
that the mean of the three sections at and be-
low the Long bridge will give fair approxima-
ton to the natural lOw-water channel-way Of
the river. The mean thus found is "a $40 square
feet With channel way of 1000 feet the mean
depth should be 1927 feet. With this mean
depth the extreme channel depth should be over
twenty-five feet. The mean Of the sections on
the bridge for the present main channel is 81 1856
feet, the width is about 2. 600 feet or deductinp
one-twentieth for piers and instructions, 1, 800
feet. The mean depth is 11.24 feet, and the ex-
treme depth about 26 feet.
The sectional area Of the proposed channel at
the Long bridge, assuming rise at that point
feet; the present area is A. 1874 feet 1t will be
necessary then to take out the causeway now
existing at the south end of the bridge, 2l9 feet
in length, to the lOW-water mark. This will in
crease the area to 36l7 feet.
During the freshet of 1877 the rise at Easby's
Point Ia feet at 18th street, 10 feet; at the
Long bridge, feet. and at the Arsenal, "a feet
above low water. The relation between these
different heights shows that the Long bridge
presented no obstruction to the free passage Of
the waters. As measure Of safety it might be
we'll to carry the bridge, in trestle, for a dis
lance sufficient to give total high-Water Sec
tiOnal area Of d GOO feet
The river at Easby's Point is reduced to low
water SeCtiOu VI l9SUU Icel, d0ue0 TO Which the
conhguratiOn Of the shore is such as to throw
the current Of the main channel strongly against
the Virginia side and to form q broad mOrass
under the lea of the point. 1t is extremely inn
portant that all the wharfage line down to 18th
street should be preserved and that there shOnld
be uniform depth along the whole Of this 'front.'
age. The channel should therefore be opened
by cutting Of the point giving it an area as great
as it can probably maintain; that Is, about a. 900
feet II the depth along the bulkhead is as
sumed to be % feet, there will be 222 feet 10 be
cut from the point. The excavation will. be
mostly in rock, but the greater part in open
cutting. 1t seems most probable that the point
OF AnalOstan island should also be removed to
the depth OF about six feet below low water in or
der to throw the main channel more easily AGAINST
| the proposed line Of the Washington shore
This is. however. matter of no pressing impOr-
lance, since the direction of the main channel
may be controlled by retaining wall, composed
OF rough stone. carried down from the island
ID the position indicated. The channel at this
point should be about 500 feet in width. With
rise of 10 feet in time of flood. the sectional
area would be 80, 900. The channeIway back of
AnaOstan island. or the section of the river.
should then be opened to such width as to give
about ,OO0feet additional area. BY this meansthe
flood-iine along the Georgetown wharves would
be lowered about three feet. 1t would seem
better. II possible to avoid opening the AnalOs-
ton shute on account of disturbing the regimen
OF the river below. This might be done by cut
at the head of the island. This. however. is q
matter which may be left for future considera-
ton. We may say with certainty that the bar
in the Georgetown channel will disappear when
/ the works here outlined shall have been com
pleted.
The inside channel being stopped at the Long
bridge, will become al inside basin. With such
an arrangement proper means must be taken to
keep the water in . pure and wholesome cOnd-
| ton. To accomplish this end flushing or sluic-
ing basins are to be provided the present flats
above the bridge. into which the water from the
| outer channel may be- admitted at high tide by
automatic gates. The waters so accumulated
Will be used to flush the inner channel on the
last third of the ebb tide. The total area of
these basins is 100 acres. AS the mean rise of
the tide Is three feet, the quantity Of pure water
passing from them into the inner channel with
each tide will be about IA, 600 600 of cubic feet
The entire contents Of a channelway of 500 feet
wide, with mean depth of IL feet, will be
600 cubic feet. The infiOwing tides will
supply q. 600 Goo while the flushing basins will
supply 2S.0O0,0OO Thus the water will be en-
entirely displaced each day. For a channel of
greater dimensions larger basins may be pro-
vided below the present causeway.
With this general scheme the fats to be re-