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

f0rmable by the alteration in the position Of the
cross section of the present channel
In making the calculations for the improve
ment Of the river 1t was Necessary to determine
| the low water sectional area which should be
adopted as standard. The average sectional
area Of the river between the AQueduct bridge
and Easbys point was found to be 10 1916 square
feet, and for the Georgetown channel between
Easbys and the Long bridge, oO,679 square feet
The sectional area at the Long bridge was be-
| lieved to present the conditions necessary for
determining tn area which should be assumed
as the standard in the calculations for the i'm
provement. In these calculations the heights of
freshet assumed are those of the freshet of 1877
which was actually higher freshet than that of
1881, the greater elevation of the latter above
the Long bridge being due to the ice gorges at
that point as already stated.
The cross section taken parallel with and so
feet above the Long bridge, showed the sec
tional area Of the Georgetown channel to be
| 81 ,051 square feet. (between the lines of the
abutments). that of the Washington channel to
| be .662 square feet, and of the flats between
| 1,S26 square feet. The sectional area of the
Washington and Georgetown channels together
at this point is q. 7l3 square feet.
From this point to the Arsenal wharf.-the aver
age section of the two channels together is about
4,oC0 square feet. not including the flats be-
| tween them. As the Georgetown channel will.
upon the completion Of the improvements. be
called upon to discharge the entire body of the
| freshet water, its 1Ow-water section should be
| equal to the combined section of the two chan
| nels and in view Of all the facts ascertained by
| the survey, the standard low-water section has
been assumed at Is, 600 square feet.
The sectional area of the freshet of 1877 has
been assumed as the standard in providing for
the freshet discharge.
A sectional area of 4S. 600 square feet. with a
rise of ten feet. has been provided for at the
Long bridge. In order to discharge this through
| the Georgetown channel it will be necessary to
remove the causeway, which forms part of the
abutment OF the southern end of the bridge for
distance of about 400 feet. replacing it by
trestle work Cor spans of bridge similar to those
now in use), the causeway to be removed to a
depth of three feet at low water. so as to allow
| the tide to flow underneath it.
The sectional areas above and below the
bridge will be sufficient for the discharge of the
water of freshets.
l. The low tide sectional area assumed as
standard is % 600 square feet.
2. The high tide sectional area assumed as q
standard is 81 .S75 square feet.
8. The freshet area assumed as a standard is
1000 square feet.
The limits of the flats to be reclaimed. as con-
templated in the act by means of the dre(lned
material the port warden lines Tor the Wash
ington channel. or inner harbor as well as the
outer port warden line beyond which neither
whalves nor landing slips will extend are indi-
Gated On the accompanying tracing. The harbor
INES are not indicated precisely on the map but
will be fully laid down on later maps which en-
body the fuller results of the survey.
On the Georgetown channel the harbOr line
commences at Easbys wharf. following a curved
line. as shown on the plan, to the southerly end
of the causeway of the Long bridge: thence on
curve, nearly parallel with the river channel
| to point on the flats below the Arsenal wharf
| at the intersection of the two channels.
For the Washington channel. the inner line
| follows nearly the limits of existing wharyes
and the outer line of the Washington harbor is
$40 feet from the inner line. The inner line
beyond which 1t is recommended that no wharves
| be allowed to extend, is as follows: Commencing
! at point 25 feet outside the northwest corner
| OF Riggs wharf, running thence in a straight
| line to point Is feet outside the southwest
corner of the lower wharf of the Great Falls Ice
Co.. thence in a straight line to a point % feet
| outside the southwest corner of Evans stone
wharf. thence in straight line to point 25 feet
outside the northwest corner of the third wharf
below the Alexandria Ferry Co.'S Slip thence i'm q
straight line to the southwest corner of the
wharf of the Inland and Seaboard Co.,
and continuing to point 40 feet above the
first angle in the Arsenal wall and 22O feet west
of said wall. thence to point $50 feet outside
the Arsenal wall at the site of the old peniten-
tlary wharf. thence to a point 10 feet west of
| the northwest corner of the existing Arsenal
| wharf
| The Washington channel above the Ion @ bridge
| is LETT open as far as 18th street.
The greatest depth of the sectional area of
discharge is assumed as equal to the greatest
depth of the proposed channel. the assumption
, ebb and food tide.
The part of the channel south of the reclaimed
| area, being partly an estuary of Chesapeake Bav
may nave low-water sectional area greater
| than the lOw-water section of the river at that
point. without any alteration of the present low
water surface of the river.
The tidal area excluded by the Improvement
VIII be about go acres. While the exclusion of
| tidal water i'll harbOr improvements is not to be
desired, in the present instance it cannot be
no of oh,
! however facilitate the propagation of the tida.
wave. and will in some degree compensate for
the exclusion of tidal water.
IMPROVEMENT.
The general plan of Improvement consists in
dredging the Georgetown channel to a maxi
mum depth of % feet, with bottom width OF
| dredged channel not less than 400 feet SO as to
give low water area of q, 900 square feet
| dredging the Washington channel between the
Long bridge and theArsenal wharf to a width of
4OO feet at the bottom and depth of 90 feet at
! low water, and thence to the outer wall. where
the depth will be 5 feet, the dredged material
! to be placed upon the flats. so as to Use them
them to height of feet above low water. this
area to be protected from freshets by means OF
an embanKment around the edge of the re-
| claimed area, with provision for drainage 1t
| may further be desirable to dredge out a basin
| above the Long bridge and along side of the pre-.
| sent sewer canal to scour out this canal at low
\
provement may be varied somewhat, 1 have pre-
pared the following estimates
! ESTIMATE NO. 1.
| The dredged material to be deposited on the
flats, SO as to raise them to height of 6 feet
above low water, both above and below the
Long bridge. An embankment around the edge
OF the reclaimed area, SO feet wide on top, with
outer slope OF IA to l, and inner slope 3 in
100, Height 10 feet above low water above
bridge, and 10 feet below bridge. The edge of
the filling protected by wall of dry rubble ma
| sonry.
S,9402 80 Gu. yds. material dredged
and deposited on flats, at &c., 81 sos. 238
366, 020 Gu. yds. embankment at 2Oc 73.2O4
100000 Gu. yds inner slope embank-
ment, at 1885,. Observation-Disclosures. $4,000
Dry masonry wall Observation-Disclosures. 292, $40
Contingencies, 10 per cent. .. 2O6, 49S
| Total. ACKNOWLEDGEMENTS So ,2n ,4SO
| ESTIMATE NO. 2.
| Height Of filing 6 feet as above. Embankment
along Virginia avenue from 18th street to the
high ground on the monument lot, to protect
the city against floods, slope protection of rip
rap and piles.