Evening star. [volume] (Washington, D.C.) 1854-1972, 1902-09-05
TO REBUILD PIER 5
Project of Lieut.. Col Allen
Approved.
THE AQUEDUCT BRIDGE
DETAILED HISTORY OF THE
STRUCTURE.
Numerous Points of Weakness Discov-
ered-Efforts to Strengthen-Ac-
ton Taken by Congress.


600 contained in the District of Columbia
appropriation act approved July 1, last, for
the reconstruction of pier No. 5 of the
Acqueduct bridge across the Potomac river
al Georgetown.
I'm carrying on the work of reconstruc-
ton of pier No. of this bridge. provided
for in the act of June 8, 1885, says Col.
Allen, the contractors complained of diff
fculty in obtaining a sufficient number o.
large blocks of Potomac gneiss, notwth.
standing the immense deposits of that Stone
near Washington. one reason urged as ac-
counting for this was the concentrated. con
troll of quarries. No difficulty had been en-
countered, far as known. in procuring
that kind of dimension stone in 1894 and.
1895 for the reconstruction of a large part
of pier No. f. However, as pier No. 81 will
not be connected in any way with pier No.
there is no reason why the contractor for
the work of reconstructing pier No.
should not be allowed to use granite for all
stone work of the pier excepting for the
courses (cut water excepted) above low
water mark, which should be of Potomac
gneiss, relatively small amount Of gne.ss
suficing. Allowing granite as stated will
undoubtedly enlarge the range of bids.
1t is regarded desirable that the gneiss
be used as stated on account of all of the
other piers and the shore abutments being
of that stone, and in order not to have un-
necessary and undesirable contrasts of
color and general appearance that would
most probably be impracticable to avoid
were stone other than gneiss to be allowed
for the pier courses above the water sur
face.
1T is respectfully recommended that the
said appropriation of So, 900 for the re-
construction of the aqueduct pier No 5.
made by act of Congress of July /, 1902, be
from the bottom up All of the existing
pier should be removed to solid rock, a
proper foundation prepared, and the new
pier then built up with heavy quarry
faced ashlar masonry for the faces of the
pier, the hearting to be of concrete or rub
BILE masonry, all laid in the best cement
mortar. The coping and such other per-
lions of the stone now in the pier as can
be suitably utilized to be used in the new
work.
1T is proposed TO do the work by con-
tract, after public advertisement. inviting
proposals for the work, the specified tons,
including usual form of advertisement, to
be submitted to the chief of engineers as
soon as possible after the approval of the
project. 1t is proposed to take a few
soundngs and probings in the immediate
vicinity of pier No. 3 in order to verify
depths TO rock. ...,;
with this is a tracing, showing the
present and also the proposed new pier.
The new pier does not differ materially in
plans in cross section from the old pier, ex
cepting that the offsets at the bottom are
omitted as unnecessary. The present pier
supports the ends of two fixed bridge spans.
which ends will have to be supported by
the new pier. For this, we'll as for
architectural and other reasons. not omit
ting to mention the wording of the act, the
proposed new pier five. in plan and sec
ton, is about the same as the present pier
five. The numbering of the piers begins on
the Virginia side of the Potomac"
The Original Piers.
The piers of the Aqueduct bridge, con-
structed to carry the Chesapeake and Ohio
canal across the Potomac river at George
town, We're built about 1S35-1S40. They
are composed of Potomac river gneiss. eX-
cepting the icebreakers, which are Of gran
lite. Between the main river abutmentS
! there are eight piers about 40 feet apart
| between the faces at the tops, Every third
pier is about sixteen feet wide at the top,
the remaining piers have top widths of
about seven feet six inches. The top. of
each pier is about thirty feet above the
plane of mean low tide. These piers were
built within cofferdams and were supposed
to have been constructed of substantial
masonry founded directly upon the rock
bed of the river. There appears to have
been many difficulties attending their con-
struction.
According to the original plan adopte
the superstructure was to have consisted
of nine stone arches the two broader piers
to serve as sectional abutments. For eco
nom1cal reasons, however, a wooden truss
bridge and trough Of kyanized timber We're
substituted.
This structure was the Potomac aque-
duct"
In 1866 the Alexandria Canal Company
leased their canal and the bridge (Aqueduct
BRIDGE to Messrs Quigley, Wells and Du-
gan for period of ninety-nine years. The
lessees replaced the old truss, which had
become decayed and unsafe, by a Howe
truss, and the latter was subsequently
strengthened by wooden arches BY act of
Congress approved July 81, 1868, the Iessees
were authorized to erect and maintain. in
connection with the aqueduct, a highway
bridge and to charge certain specified rates
OF toll. floor system was placed on the
top chord of the Howe truss, trestles and
spans Tor the approaches were built and
the bridge used as a highway until 1885,
For several years prior to the last-named
GATE, however, the condition of the bridge
was not deemed satisfactory, and two ex-
amina tons in detail were made Of it. under
the direction of the chief of engineers and
the results reported to Congress Roth
examinations resulted in reports to the
effect that the bridge superstructure wa
UNSAFE for public travel.
Free Bridge Established.
An act Of Congress approved June 81
1885, provided for the establishment of a
free bridge, either by the purchase of the
Aqueduct bridge piers and the erection of
an iron bridge thereon, or by the construc-
ton of a new bridge at or near the Three
SISTERS, about one-half of a mile above the
Aqueduct. Under the provisions of this
act the bridge was purchased by the United
States. The existing iron superstructure
was constructed by the engineer depart
ment, being completed in 1888
On September Is, 1888, the custody of
the bridge was transferred to the District
Commissioners in compliance with a re-
dnirement OF the District appropriation act
Attention appears to have been first call
ed to the defective construction of the
piers Immediately after the freshet of June.
1889. The sectional area of the river is
much contracted at the site of the bridge
by the number and size of the piers and
especially by the extension Of the embank-
ment of the south approach into the river
The effect Of this embankment Is to pro-
duce violent eddies during freshets in the
vicinity of the first pier from the south
end of the bridge, known as pier No l.
soon after the freshet had subsidized pier
NO l was observed to have moved several
inches to the northward and a nearly YER
tea, crack was also noticed extending en-
tirely through pier No. T. which was sltu
eted about in the center of the channel
from the coping down to low tide, at least.
An examination by diver revealed the
fact that the movement of pier No l and
the crack In pier No were both due TO
the erOSion n he ho of