Evening star. [volume] (Washington, D.C.) 1854-1972, 1894-03-21
TAKING PRECAUTIONS
Need to Strengthen the Aqueduot
Piers Before Allowing Railways.
WATCHING AN EXTENDING CRACK
Two Reports on the Subject of the
Bridges Stability.
OTHER REP AIRS NEEDED

There is no Disgusting the fact that there
is considerable anxiety felt in the engineer
department regarding the safety of the
Aqueduct bridge.
Ever since the first pier at the Virginia
end of the bridge began to move and iuvesti-
cation showed that the water had under
mined the substructure, the engineer de-
partment has been particularly careful re-
garding inspections of this bridge Each
day the piers have been carefully examined
and the superstructure tested to insure its
safety. Recently small crack was dis
covered in the fourth pier from the Virginia
end OF the bridge. 1t was an innocent
looking opening, but the engineers OF the
District and the United States engineer in
charge Of the Virginia end of the bridge
were hurriedly summoned.
Maj c. E. l.. B. Davis the enpineer in
charge of the Potomac flats IMPROVEMENT
was detailed by the Secretary of War 10
make the examination, and his report on
tne condition Of the bridge was recently
South Abutment.
The south abutment was found to be rip
raped on the river face below a depth Of
seven feet at the west end and eleven feet
sonry was found in excellent condition from
low tide down to the riprap.
Pier No. 1. counting from the south a,ut-
ment is the pier which was partly under
mined at the west and northwest ends by
the Hood OF June, 1889, and repaired tnder
.ne direction OF the District Commissioners
with Portland cement concrete In bags.
placed In the eroded cavity by divers AZ
ter the concrete was placed 9a2 tons of rip-
rap were placed about the pier. The top
OF TINS riprap was found, May. 1897. TO he
about fifteen feet below low tide at the west
or upstream end Of the pier and about
twenty-six feet below low tide at the south
east corner.
Pier No. 2.
Pier No 2 was found to be in good copd:
ton, except a cavity about one ari n half
feet deep and two feet high around the west
end This cavity is between the bed rock
which Is quite irregular. and Two r,nbers
which are halved together, forming an an
gle at about the center of the west end Of
the pier These timbers rest On the bed
rock at their outer ends and faay have
rested on some loose stones at other D -.uis
which have since been removed by the ac-
tion or the current. But it is more proi.a-
pie mat the timbers formed a part of he
coner dam and that the foun Ia tim course
was laid inside the umbers, and the ncxt
course projecting a little further than he
former covered the upper sides. ami that
ledge has always existed.
me ped rock was exposed around the
west END and the rest of the pier WAS sur
rounded by a bank OF sand
Pier No. ,.
A cavity extending nearly the whole
length of the south side of thi. pier was
found. This cavity is about 3 feet high
above the riprap and 3 feet deep. but as
the foundation courses project about 6
feet beyond the side of the main pier the
cavity Is not as serious a defect as II
might appear.
There is, however, a large cavity I'm the
west end. which starts under the ice
breaker at course about 8 feet below
low tide. where it is about feet deem
measured lengthwise of the pierl and
extends entirely across the end of the pier
AZ the southwest corner of the pier the
oepth or the cavity is IL feet deep. or
about feet deeper than the average dentb
IL is probable that the erosion started near
the bed rock in the foundation courses
which were worn and displaced by drift
ing DEBRIS. and that as the cavity deep
ened the stones above fell from their own
weight and now lie. together with several
small trees. scattered about the end of
the pier. A large tree was found on the
bottom lying across the. upstream end
or the pier, which was probably a factor
In the initial erosion of the masonry.
Ihere is crack extending entirely
through the pier from the top of the coping
1t was so small that the diver WAS unable
to follow it. The location of this crack. as
SHOWN on the elevation Of this pier is only
ABOUT tnree-eighths of an inch wide at the
widest part The crack is more marked
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 the
pier Ripraps was found along the sides
AT depth or about twenty-five feet below
low tide, and a bank of mud fifteen feet
below low tide at the downstream or east
end ~
No serious defects were discovered in this
pier one of the stones in the ice breaker
just north of the center and at low tide has
started slightly.
North Abutmcnt.
This abutment is i'm good condition. except
few places where the mortar is out of the
races OF the joints. The water is only about
I'D feet deep TO the mud which was found
around the foot of this abutment
Masohar! OF Piers and Abutments
Above Low Tide.
lhe masonry of the piers and abutments
above low tide is in good condition with
the exception of the crack already noted
on pier No. 4. All of the masonry above
low tide was carefully pointed with Port
land cement in 1869 when the bridge WAS
reconstructed, and the pointing was found
intact.
Levels were taken on bridge seats of all
the piers and abutments. These bridge
seats are of granite. the tops being bush
hammered cut work, affording good sur
faces on which to determine precise eIeva-
tiois Of the coping.
These bridge seats We're set at a uniform
grade of 81 feet above mean low tide of the
Potomac river Improvement The levels
taken in May, 1888, show no appreciable
variation beyond such as are due TO ir-
reguiarities in the dressing or setting of
the stone. except upon pier No. / The diff
fcrences in level found here are due to the
movement in the freshet of 1883 Piers
Nos. to S, inclusive are plumb Pier No
l has moved to the north from the under
mining of the freshet of 1SS9 that the
batter of the north face is now 0.O1J feet
per foot. and of the south face 0.U95 feet
per foot. Between the top of the coping
and high tide mark the pier is out of plumb
J2-loo of a foot The pier, however, is in
a condition of stable equilibrium and no
serious results need be apprehended from
tix -alx- eli laxri.