Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-03-30
WAS NEVER FLOODED
Coferdam Keeps Water From
Post Office Department Cellar.
ACTION OF VALVES
OF CHIEF ENGINEER
O'DONNELL.
Col. Biddle's Opinion-Inquiry Caused
by Assertions in Yesterdays
Senate Debate.

In the discussion in the Senate relative
to the use of the south side of Pennsyl-
vania avenue for the erection of pubic
buildings yesterday Senator Nelson said
that the Post Office building had been
flooded during the high waters of the Poto-
mac, and that such calamity might be
expected at any time when the waters of
the river rose beyond their natural bounds.
This condition, 1t was asserted in the de-
bate, might be brought about by the jam
ming of ice at the Long bridge or by other
holding of the waters that were seeking an
outlet into the bay. Arguing along these
lines it was held that to erect great public
buildings on such treacherous soil would
be the height of folly. AS a matter of fact,
however, the engineers at the Post Office
building say that there has never been
food there, and that SO long as the waters
do not rise on the street to a higher level
than the cofferdam surrounding the build
ing there can be no danger. Before the de-
bate closed Senator Fairbanks announced
that he had telephoned to the Post Office
building and had ascertained that the base
ment had never been flooded.
The Building Never Flooded.
reporter for The Star today had an op-
portunity of visiting the engine rooms of
the Post Office Department building. He
heard from the chief engineer, Mr.. James
ODonnell, that not only had there never
been a flooded condition of the building,
but that such thing was impossible under
the circumstances of protection which nave
been installed there, unless the waters OF
the Potomac rose above the cofferdam sur
rounding the building, condition which Is
not expected if previous high waters are
safe to use as precedent.
In modern building construction the cof-
ferdam plays a highly important part
said Mr.. O'Donnell land without 1t the
basement space would be impossible The
floor of the basement of the Empire build
ing in New York is perhaps sixty feet be-
lew the high water level OF New York bay,
and yet there has never been flood there.
The cofferdam saves it, of course. Persons
not having familiar knowledge of modern
building construction cannot understand
this method of keeping low levels perfectly
dry, but it is extremely simple. When
foundation is laid the cofferdam is built all
around 1t and to such q level above it that
all danger OF flood from either superficial
or subterranean drainage is averted.
In addition to this precaution is the
system of back pressure valves that are al
ways at work WIN automatic regularity.
This system renders flooding by a sudden
downpour of rain an impossibihty, for the
reason that when the sewers are flooded by
the sudden accession of water from the
roof and from the streets the valve prevents
the water from rising and backing into the
building. 1t is SIMPLE valve that works
with the pressure If the pressure is greater
in the sewer it holds the valve shut tight,
and If 1t Is greater in the pipes leading to
the sewer it forces the water into the sewer
at high pressure and drives it toward it's
natural outlet
Height Of the Cofferdam.
''The cofferdam on the outside of the post
office building is, / am informed, higher
than the l..ghest flood ever known in the
city, and in order for there to be any danger
of the basement of this building being
flooded it would be necessary for the river
to rise so high that the water would come
above that record level. We have never
experienced the slightest anxiety here save
on one occasion, when there was heavy
rain that flooded the sewers and caused
them to back water so rapidly that they
and for time threatened trouble But
we put the engines to work and soon had
1t cleared After that the back-pressure
valves were put in and there has never
been any trouble since.
There are three drip wells in the base
meht." said Mr.. O'Donnell, and he con-
Quoted the reporter to them SO that ne
might see for himself what they were. He
mon to all engine rooms and were for the
purpose of catching and carrying off the
waste of the engines, which are below the
level Of the sewers. The waste is con-
stantly dripping into these wells and as
regularly being carried off by pumps that
are always busy and which raise the water
to the level of the sewer which then does
its part In the work. There is a well at
the c street side OF the building that Is
intended to take care of any water that
might possibly find its way into the build
ing by percolation. but it has never been
used and is maintained there only as
S ifeguard in the event OF a possible require
EleDt in time of great emergency.
1T is the opinion of all the engineers en-
ployed in the post office building that there
has never been any danger of flood and
that there never win he unless the waters
OF the Potomac rise above the cofferdam.
That invention protects the building. they
say. perfectly, and IL danger of food is the
chief objection to utilizing the south side
of government buildings that fear can be
eliminated from the plans"
Col Biddle's Opinion.
Col John Biddle. Engineer Commissioner,
when asked for his opinion as to the pos
slbihty that the cellars of public buildings
located south of the avenue might be Hood
ed. said that he did not consider that any
serious damage was likely to result from
that contingency
'The building of suitable and safe founda-
tions south OF the avenue he said, would
probably be more expensive than If they
were constructed higher ground, but
with proper construction of foundations and
easements think there is danger to be
feared from possible floods. The cellars
can be protected with proper construction.
when the new sewage disposal system
has been completed continued Col Bid
die, 1.-The danger of floods in cellars along
the avenue will be still more greatly de-
creased"
Assistant Secretary Loomis Returns.