Evening star., 1896-03-09
DEFECTIVE PIERS
Money Asked to Repair the Aque-
duct Bridge.
Old TREES In The MASONRY
Recent Discoveries of Early Bad
Work.
THE FUNDS REQ UIRED

L IL T. u N u Ii Il ~ u II T. u
1t is the hope of General Craighill, the
chief of engineers, that Congress will at
this session make an appropriation that
will enable him to make certain important
repairs on the AGueduct bridge, for which
he has estimated $4,000 to be necessary.
This estimate was submitted January 20,
too late for the item to be included in the
District appropriation BILL as it left the
| hands of the subcommittee of the House
and is now awaiting action in the Senate
committee. AS is well known the Dis
trict ill was defeated in the House
| and recommitted with Instructions to
wise the charity schedule, but it is hoped
that the subcommittee may see its way
clear to insert this item. which is regard
ed by the engineering authorities as of
great Importance.
An Old Menace.
The AGuedrct bridge has been a source
of trouble and anxiety for several yeals.
1t was long thought to be of exceptional
soundness ard strength. for the local tradi-
ton was that it's piers were built on bed
rock in the most substantial manner. The
first suspicion against their integrity was
aroused by the appearance of slight
buckle" or twist in one of the steel straps
on the side of the superstructure of the
bridge just north of the first pier from the
Virginia side during the summer of 1882
The river had been swollen with floods in
June, and IN some manner a great tree
trunk had been lodged against the pier wall
near the base in such a position that the
swift current had secured away the mud
and finally the undcrpinnng until the pier
had settled several inches to the north,
thus subjectins tie Steel framework above
1t to an unusual strain. There was consid-
erabe agitation felt at the time for it was
feared that the bridge was in serious dam
ger, and that the pier might completely
collapse at any time. A diver was sent
down, and the settling of the pier was
stopped by the insertion of bags of cement
In the gap secured out by the currents
Nearly Thousand tons of riprap was then
placed over the patch. Since then the pier
mad been regarded as perfectly sound al
thoush when it was further examined in
ls:t', Ii was found that many of the joints
Were more or less open, through the loss
of mortar
An Examination Ordered,
In lS'si resolution was passed by Con-
gress directing thorough examination Of
all the piers to be made, defects having
oeen discovered in one of them causing
settling of several inches As a result
OF this examination minor defects were
found in all Of the piers. while pier T. from
The Virginia side. was discovered to he i'm
very bad condition. The following sum
mary of the defects was subsequently.
L.. b. n
gineer then in charge: "a cavity extend
ing nearly The whole length of he south
side OF TINS pier was found. This cavity
Is about three feet high above the riprap
ana tnree 1eet deep but the foundation
courses project about eight feet beyond the
side of the main pier the cavity is rot as
serious defect as it might appear
A Large Cavity.
There is, however, a large cavity in the
west end which starts under the ice
breaker at course about eight feet below
low tide. where it is about seven feet deep
measured lengthwise of the pier) and ex-
tends entirely across the end of the nier
AT the southwest corner of the pier the
depth of the cavity is eleven feet or about
four feet deeper than the average Geptb
1t Is probable that the erosion started near
the bed rock In the foundation courses,
which were worn and displaced by drifting
debris, and that as the cavity deepencd the
stones above fell from their own weight
and now lie together with several small
trees scattered about the end of the pier
large tree was found at the bottom
lying across the upstream end of the pier,
which was probably factor in the initial
erosion of the masonry: The extent of
the cavity Is shown on the plan and eleya-
tions of pier No. 1, on tracing No. l. ac-
companying this report
There is crack extending entirely
through the pier from the top Of the ccp-
ing down to low tide and probably fur
ther but it was so small that the diver
was unable to follow it. This crack is
only about three-eighths inch wide at the
ON the south side of the pier than ON the
north side. The crack is plainly due to
the undermining of the upstream end of
lhe pier. Riprap was found along the
SIDES at a depth of about twenty-five feet
below low tide and a bank of mud fifteen
feet below low tide at the downstream or
east end
Money for Repairs
In accordance with the report made in
response to the inquiry, Congress inserted
in the District bill approved August :, 1891,
oppropriating for the fiscal year that ended
June 30 last, an item of SOL ,O7O for repair
of the bridge, including the bracing I'D of
piers =, s. q. and by means of concrete
in bags, and the complete strengthening of
pier with the use of a Golfer dam. The
contract for this work was let September
26 1894, to Smaller & schniglau Co. of
begun a month later and continued
throughout the winter when the weather
would permit. Maj Davis reported as fol-
lows to the chief of engineers concerning
Ire state OF affairs uncovered under pier
number 4, November 80:
After the cofferdam bad been pumped
out and the masonry below the water line
was exposed, a most unexpected and sur
prising condition of affairs was revealed
1t was found that the timber cross-braces
of the old original cofferdam built in 1880.
sixteen inches square and twenty-one in
number, had been left in the pier and the
masonry built around them. 1t was also
found that the old masonry had not been
started from solid rock. as shown on the
original plans, but upon riprap stone ap-
parently thrown in to level off, without
removing the debris upon the rock which
Is fissured and scanned and has many pro-
jecting nOduleS.
had Work Done at the Start.
Layers of mud and sand were found
| under the lowest of the old shores, while
lyirg on the rock dagonally under the ma
sonry Of the pier old tree was found
which must have been there before the
pier was built. For about twelve feet
above this insecure foundation the masonry
is of the poorest quality possible and hard
SPECIAL NOTICES.