Evening star., 1896-07-20
BRIDGE
Major Aliens Report Of the Work Of
Repair.
BAD CAVITIES FOUND IN PIERS
Difficult Operations Successfully
Completed Without Mishap.
Me MON saw ED

In his annual report to the chief Of en-
gineers in regard TO local river and har-
Dor improvements Maj. Charles ]. Allen,
the engineer officer in charge. gives an in
teresting history of the efforts made to
complete the project for the repair and i'm
provement of the Aqueduct bridge across
the Potomac According to his report all
the piers and abutments of the bridge were
examined by the aid of a diver in May
1893. with the following result:
The south abutment was found In good
condition.
mined by the freshet of June. 1859, and
repaired under the direction pf the Com
missioners Of the District Of Columbia with
Portland cement concrete in bags, was
found in good condition.
Pier No. "A small cavity was found at
the west or upstream end Of the pier. but
with this exception, the pier was found to
be in good condition.
Pier No. 3-The greater part of the pier
was found in excellent condition, but the
foundation courses had been eroded around
the west end.
Pier No. 4-This pier was TO md to have
been seriously injured At the upstream
end of the pier large cavity was found
extending from about feet below low tide
down to bed rock, about "a feet below low
tide, estimated to be from to II feet long
measured lengthwise of the pier) and ex-
ttnding entirely across it under the ice
breakers. TIE erosion had evidently start
ed near the bed rock, where large tree
was found. the everything stones of the ma
sorry having fallen as they We're gradually
undermined This erosion had caused a
slight settlement of the west or upstream
eEd of the pier, and as a result of this set
Gement nearly vertical crack had ap-
peared at about the center of the pier. The
ipht ha Of
wide and was more marked at the so Ith
than at the north side in this pier.
Pier No. mo serious defects were found
in this pier.
Pier No. ca cavity about feet long
5ls feet high and 3 feet deep was found at
the northwest corner of this pier, but the
remainder of the masonry was in good on
dition.
Pier No. IA cavity was found in the
foundation Courses at the west end of the
pier, and another slight one on the north
side of tae pier. The rest was in good con-
diton.
Pier No. S-This pier was in good condi-
ton. except on the southwest corner. where
4 cavity seven feet long. three feet deep
and two feet high was found
North abutment-The north abutment
Was found in good condition.
The masonry of the piers above low tide
also was found in good condition. having
been carefully pointed with Portland ce-
ment mortar in 1885, when the bridge was
reconstructed
Repairing the Damage.
June p. 1893, a detailed report of the ex-
animation was made. July II, 1S93 an es-
innate of the cost of the repairs was sub
mitted. amounting to s51,O7O. 1t was pro-
posed to repair Pier No. by means of a
Golfer dam, within which the defective
masonry was to be rebuilt, and to repair
the remaining piers with Portland cement
concrete In bags. put in place by diver.
August Z, 1884. an appropriation of SOL ,o1H
was made IN the District of Columbia ap-
preparation act for the fiscal year ending
June 3o. 1885, for the repairs of the bridge
September 20. 1894. contract was en-
Company of Chicago, ILL.,, for the repair of
some of the piers by Portland cement con-
crete in bags put in place by a diver, and
for the repair of pier No. by means Of
Golfer dam. within which new masonry was
to be laid in the eroded cavity, the bridge
spans resting on pier No. 4. to he sup
ported on false work during the repairs, to
provide against any possible further failure
Oh the pier when the water was pumped
out OF the Golfer dam, and the effective
weight of the overhanging masonry of tie
upstream end thereby increased. The con-
tract was to be completed by the 31st of
January, 1895. but it was extended to Sep
tember 80. 1895.
Progress of the Work.
Maj. Allen tells of the progress of the
work follows:
after the Golfer dam had been pumped
out and the debris disposed Of the over
hanging masonry of the ice breaker was
moved. in order that the reconstruction
Of this part of the pier might be safely
prosecuted This masonry, which was just
above the eroded cavity, was found to be
well laid in lime and mortar, and was re-
moved with some difficulty, the work hav-
irs been completed June Is. The removal
of the debris below the eroded cavity was
next undertaken. the excavation being car
ried down to solid rock and as far down
stream the first line of cross-braces Of
the original Golfer dam of 1898. which tim
bers-twenty-one in number-had been left
In place and built into the masonry of the
pier. AS this work went on it was found
that the old masonry had not been started
from solid rock. and part Of it was of poor
quality.
The acting secretary Of war and the
chief OF engineers made an inspection of
the work June "a, 1885, and, in view of the
poor quality of the masonry at the base of
the pier, it was decided that after the COM
pienon OF the present contract flor the up
stream end of the pier), it would be neces-
sary In the Lear future to remove the de-
fective masonry in the remainder of the
pier and replace 1t by masonry of proper
quality. founded on the solid rock. The ex-
isting appropriation was insufficient for
this purpose, and 1t was therefore neces-
sary to ask a further appropriation from
Congress The Golfer dam would be needed
was therefore modified as to provide for
the purchase of the Golfer dam from the
contractors for the sum Of $1,000 in lieu of
its removal by them, for which last they
were to be paid $1,5O0, and were to have the
timber.
Difficult Task.
In order to excayate to and start the
foundation of the new work on solid rock
it was found necessary to build an inner
dam of sheet piling three inches thick
around the foundation area Of the west end
Of the pier. This dam reached to a level
of about SIX feet below that drained by the
large pump. and a steam syphon was used
t. keep it clear. This small dam broke in
several times from the pressure of the wa
ter. but was held on June 10, 1895 so that
the excavation could be carried down to
solid rock, and on June 80, 1895, this ex-
cavatioa had been practically completed
The bed rock was found to be very irregu-
lar and covered with small projecting spurs
or nodules, with corresponding depressons
or valleys. The general level Of the rock
plateau uncovered WAS about twenty-four
feet below low tide, but at the extreme up-
stream end of the base Of the pier as it was
10 be rebuilt a deep cavity was found, cury-
ing under the overhanging shelf Of rock. the
lowest part Of the cavity being about thir-
ty-one feet below low tide.
AT the close Of the fiscal year ending
June 30 1895, $i3,3..9.O3 of the appropria-
ho1 daa