Evening star. [volume] (Washington, D.C.) 1854-1972, 1915-07-10
Recent Accident Threatened
to Affect Seriously Success
full Operation of System.
DAMAGE DONE BY SOIL
SEEPING INTO THE PIPES
New 24-Inch Terra Gotta Conduit
Laid at Station Near the
Soldiers Home.

one OF the dig drainage pipes at the
District filtration plant just south of
the Soldiers Home grounds developed
a leak recently that but for prompt
discovery and repair might have at
fected seriously the successful opera
ton of the filtration system. Informa-
ton regarding the accident was with
held from the public for prudential
reasons until the necessary repairs
had been made and the service was
again in perfect working order. The
accident was of a most unusual type
from an engineering standpoint and
was made the subject of a special re-
port by Capt. Charles L. Hall, Corps
of Engineers, one Of the assistants of
Col. Newcomer, the engineer officer in
charge of the District water supply
system. "A peculiar feature of the mis-
hap was that the damage was DONE
not by the water escaping from the
leak, but by the surrounding soil of
sandy loan seeping into the pipe and
draining into the city's. sewers.
Capt. Hall Describes Accident.
The filtration plant" said Capt. Hall,
In describing the accident, Consists of
number of filter beds. which are To-
Gated in adjoining blocks, separated by
open spaces called courts. These courts
are all paved over with six inches of
concrete paving, the only interruption
in the paving being small plots In
which trees are grown. The soil under
lying the paving is sandy loan, a large
part of which was removed and then
replaced when the filtration plant was
completed. This removal was necessary
in order to lay the sewer pipes. The
sewer pipes are used, among other
things. for draining the filter beds when
1t Is desired to discharge the water
from the beds. not into the filtered
water reservoir, but into the city sewer
In order to secure the necessary head.
SO that the sewer can discharge by
gravity, the pipes were laid at con-
siderable depth.
I'm court No. l there was laid in che
same year that the filtration plant was
constructed G905) a twenty-four-inch
terra-cotta pipe, with bell and spigot
joints, calked with cement mortar.
The pipe was sixteen feet below the
level of the court paving. The soil i'm
mediately everything it was extremely
sandy.
Tree Nearly Disappears.
"The first indication of anything
wrong was the almost total disappear
ance at am. of a small tree placed In
one of the open plots of the court pre-
viousIy mentioned. The court pave
ment was Immediately taken up, when
it was discovered that the surface lay
err of earth had dropped. leaving a cav
ity about fifteen feet wide, twenty-four
feet long and nine feet deep. This sud-
den drop of a large mass Of earth evil
IDENTIFY occurred at the same time as
the falling of the tree, and completely
smashed the pipe for distance of six
teen linear feet.
"The cause of this break was doubt
less leakage in the joints. which al
lowed the water to leak through and
liquify the sandy material to such an
extent that 1T entered the pipe and was
carried along with the water. Begin
Qing with small leak, the material
surrounding the drain was gradually
carried through the pipe to the sewer,
causing settlement and small breaks in
the pipe The process probably had
been going for years and became
apparent only by the dropping of the
supporting surface layer of earth. The
archtng effect of the earth had evident
ly supported the earth itself, and the
arching effect of the concrete pavement
had evidently resisted the ordinary
highway pressure on the court. It will
thus be seen that there had been taken
away gradually. without it's becoming
apparent. a total of 120 cubic yards of
earth.
New Pipe Is Installed.