Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-02-08
TESTING THE TUNNEL
Gen. Casey Believes the Work Can Be
Utilized
History of the Tests by Experts and
the Condemnation of the Project
How 1t Might Succeed Now.

Inc senate mas pdSScu Tic DioeiASS oAAA
with an appropriation of $2o.OOO Tor test
ing the aqueduct tunnel now piercing the
hills north of the city, for the purpose Of
determining the amount Of its leakage and
ascertaining the possibility of its being
used as a part of the city's water supply
system in the future. The item as it
came originally from the appropriations
committee was in the form of lump
sum of $4,000. which was to cover the
cost of general inquiry into the whole
subject Of increasing the supply, the cost
Of raising the dam at Great Falls, and the
subject of the tunnels and the new, but
unused, reservoir near Howard University.
But in the Senate this was changed so as
to separate the two matters, and now
there is in the bill, subject, however, to
change in confer ence, where the House ap-
preparation of s125,OOO for raising the dam
may be restored, two distinct appropria-
lions. one of $4,000 for the tunnel test and
$4,000 for the general inquiry.
This test was recommended by Gen.
Casey several years ago. 1t is known that
he was never quite thoroughly satisfied
with the report of the select joint commit
tee appointed to investigate this subject
In the winter of 1889. This committee
hired board of three expert engineers
and recommended the abandonment of
the entire tunnel scheme and the SubSti-
tuition therefor Of a system of water mains
EAR the surface. The board of expert en-
gineers reported answers to the twenty
two questions submitted by the congress
SIGNAL committee that indicated their be-
lief that the tunnel in any form or state
would never be available or useful as a
part of the city'S system. 1t was pointed
out that whether lined or not the tunnel
would always he leaky and subject to both
frgress and egress Of water. In the for
mer case the water flowing into the How
ard University reservoir would be polluted
by the surface drainage from the country
through which the tunnel passes. In the
latter case the water supply would be
wasted and perhaps cause great damage
to surrounding property. The experts
demonstrated by experiments in the po-
rosfty OF brick and cement walls that there
would inevitably be a passage of the wa
ter either in or out of the tunnel, espe-
cially outward. If the supply should come
eastward with any pressure. On the basis
OF one of these experiments. with the
pressure placed at eighty pounds to the
square inch, 1t was estimated that the
tunnel would lose 27.342. 900 gallons every
twenty-four hours. The only suggestion
that was made by the board of EXPERTS
was that clay might be used to prevent
perco,ation, but this was not recommend
ed on account of the probable impractical
bility OF its use under the circumstances.
Gen. Casey was requested by Congress,
through the Secretary of War, in the
spring OF 1890, to report to the Senate up
on the feasibility of completing the tunnel
and the estimated cost. In his report he
quoted the conclusions of the board of ex-
pertS OF the joint committee of the year
before, and suggested the ACCESSIBILITY Of
test OF the carrying capacity Of the tun-
hel. which he estima ted would cost about
$4,000, and which he said should last for
nine months or year. He proposed fill
Ing the tunnel and allowing 1t to stand
both with and without pressure. in order
to observe the effect of rercolation.
ut Is evident" said General Casey in this
~ he hoav ri -
experts that no masonry lining can be
constructed in this tunnel that will be
water-tight, subjected as it will be to large
HYDRAULIC pressure. Indeed. it is not
known that any such quality was antici-
pated for the lining Its object was to
hold up the seamy and disorganiZed rock
through which the tunnel passed to pre-
vent 1t from falling into the conduit and
to furnish an interior surface that would
render the flow Of water easy and more
abundant"
1t is thus to be seen that General Casey
disclaimed all idea that the tunnel was
to be- in effect. water tight. He intimates
that he had discounted this notion, and.
in fact, he says: ''Seepage of water
through the ground and into the tunnel
can undoubtedly take place. but when the
tunnel is filled from and is in connection
with distributing reservoir, the water in
which stands at 146 feet above datum,
the pressure from within outwards will
be sufficient to force the water in the tun-
mel to level Of say 145 feet, and such
portions of the ground as are over the
tunnel and below that level will be liable
to develop springs. the waters of which
are coming from the tunnel. These pieces
Of ground above the tunnel lie in the val
leys of streams and between ridges, the
waters from which drain into these val
leys and are prevented from uniting with
the waters Of the tunnel by the outward
pressure. Should any Of the assures COM
municatng with the tunnel extend into the
grounds having an elevation Of over 145
feet 1t Is possible that the waters from
these grounds would unite with the water
in the conduit But as compared with the
quantity Of water in the tunnel this would
be insignificant and would have no effect
upon the purity Of the water passing In
the tunnel.
of water in the distributing reservoir the
outward escape will be greater than this
quantity of seepage into the tunnel. 1t is
confidently believed that the quantity of
water escaping from the tunnel when it is
fairly lined will diminish from year to
year as the veins. assures and pores be-
come clogged with the various matters
carried In silt-bearing waters. There
would seem to be no way, therefore, to
determine the extent of the dangers men
toned other than to fill the tunnel as 1t
exists today by connecting it with the dis
tributing reservoir and to observe the re-
suits If the leakage from the tunnel in
its present condition and the outflow upon
the surface Of the ground should turn
out to be less in volume than Is anticipated
then this overflow would surely be less
good condition" In concluding this por-
ton of his report General Casey says that
If the results of the trial make it appear
that 1t would be safe to complete the tun-
completing the tunnel and reservoir to
he 5000, 900, of which there was then availa-
BILE $500, O274O.