Evening star. [volume] (Washington, D.C.) 1854-1972, 1893-01-19

Some Points From the Eu.iueer's Report ~
Interest ut This Time, -


Interest nj This Time, -
In view Of existing conditions the following
extract from the last annual report OF Gen.
Casey, chief OF cngineers e. s. A.. in regard tc
tho dangerous condition Of the Long bridge. ID
interesting: In the event of o freshet occur
ring when the Potomac river 10 fall of ice
great damage is to be expected. The piers Of
tine bridge are of such faulty construction that
an ice gorge would be probable, which would
cause tho water to back up and overflow por-
tons of the city front. aud through the sewers
above the bridge such portions of the lower
parts of the city as may be drained by them.
Great damage was done by the freshet Of June,
1882 but greater damage may occur from a
freshet of lesser magnitude if accompanied by
an ice gorge"
These pertinent remarks are based on the fol-
lowing special report in regard to tho Long
bridge made BY Maj. {. f. l.. u. Davis, the on
gineer officer in charge OF the work of improv-
ing the Potomac river:
On July IA. 1891, the Baltimore and Potomac
Railroad Company submitted to the Secretary
Of War plans for the reconstruction Of tho Long
bridge across the Washington channel. The
plan adopted for the improvement Of the Po-
tomac river provides for filling up the fats at
tho head Of the Washington channel 30 that tho
greater part OF the Long bridge across this
pletion of the filling. Spans require to be
maintained. however. across the opening be.
low tho reservoir outlet, 60 as to afford passage
for the water flowing from the tidal reservoir
into the Washington channel. Tho existing
wooden spans OF this part Of the Long bridge
we're in bad condition and could not be used
much longer for the heavy traffic passing over
them. The Baltimore and Potomac Railroad
Company therefore proposed to rebuild SO
much Of the bridge AZ crosses the waterway Of
the reservoir outlet, substituting plate girdsrs
for the wooden truss, and to fill in with earth
under the remaining spans, the trusses Of which
were then TO be removed.
The plans provide for tho construction Of q
new masonry pier in the center Of the opening
and two new abutments Of masonry located 20
that their upstream ends are met by the con-
tinuation Of the wing walls Of the reservoir
outlet There are two plato gifder spans each
70 feet 0 inches In the clear under the coping.
The girders are 8 feet in depth with their
lower fanges at an elevation Of IL feet above
low tide. The foundations werc to be 6.5 feet
below low tide and the average depth Of water
between the piers and sbutments was to be 8
feet at low tide.
The plans were referred to this Office for re-
port, and repor. was submitted on July 20,
1871, recommending their approval. On July
%. 1891, the plans were approved by the Sec
rotary of War. Tho Baltimore and Potomac
Railroad Company at once entered upon tho
year the bridge proper was practically COM
pleted. On filling the approaches with earth,
however, decided and serious settlement and
movement Of the abutments were developed,
which were most marked in the southwest abut-
ment, which settled no less than eighteen
inches, while the downstream wing moved for
ward about four feet. This movement was. no
doubt, due to the pressure Of the earth filing
upon the thick stratum Of soft mud underlying
the river bed at this locality, and which extends
to depth OF about seventy-four feet below low
tide. In order to check the movement the
company have removed the earth Immediately
behind the abutments and driven piles close to-
gether in the river bed in the span opening 1t
has been necessary to support tho ends Of the
Orders in front of the south abutment by
trestles and it is understood that the com
pany propose to rebuild this abutment. The
work cannot yet, therefore, be reported as COM
plete.
The project for the improvement of the Po-
tomac river contemplated the rebuilding OF
Long bridge across the Virginia channel also.
As the improvement progresses the necessity
for this becomes more and more urgent. The
piers Of the bridge are more numerous than are
necessary in structure built according to
modern plans and IRE in a direction obliaue to
the flow Of freshets. Furthermore they are
surrounded by great quantities of riprap stone,
which has been deposited around them from
time to time to protect them. 1t is estimated
that below low tide level the natural discharge
area of the Potomac river at Long bridge 10
reduced over 30 per cent by the piers and their
foundations rs they exist today.
Long bridge, on account of Its faulty copstruo-
ton, remains q constant menace to the inter-
ests on the river front above it, and also to the
work of improvement of the fats. upon which
the government has already spent a large sum.
In the event Of freshet occurring while the
river is full Of ice the most serious results are
to be apprehended, and such contingency 10
not at all unlikely. Should An ice gorge form
at Long bridge, it would back up the waters Of
the river md overflow portions Of the city front
and, through the sewers above the bridge, such
Of the lower parts Of the city as are drained by
them.
During the freshet Of June, 1885, the water
reached height at Long bridge Of about
thirteen feet above low tide. The street sur
face at l4th and streets northwest is about
eight feet above low tide, and during the
freshet referred to the water was about Ave
feet deep in the street at that locality. Great
damage was done by the freshet of 1889, but
greater damage may occur from a freshet Of
lesser magnitude, II accompanied by an ice
gorge. The bridge should be rebuilt as recon-
mended by the board Of enQiueers