Evening star., 1896-02-22

exclusive or the cement used for the recon-
Structlon of defective or missing masonry
by hand. 1t is difficult to conceive of any
ACCIDENT (other than that which an earth
quake might occasion) to which the tunnel
would be exposed which could not be prop
cry guarded against during the completion
OF the work Yet. should any occur repairs
would be difficult and require much time"
Col. Elliot's Opinion.
The expert commission having invited the
opinion of Col. George B. Elliot. U. s. A,
retired, formerly in charge of the water
supply, that officer submitted a letter,
which is published in II. r. document 1G6,
containing the various reports on the tun-
rel inquiry. Col. Elliot in this document
answers the only objection. considered by
Major Knight as at all serious. and that is
the difficulty Of repairing the tunnel He
says:
1T is not only difficult. but it is impossi-
tle to conceive Of any accidents that cam
not be provided against during the compile
ton of the tunnel. In view of the tremen-
dous responsibility that had been put upon
him, to say nothing of the loss of SO much
money if the tur mel should be abandoned,
or of the disappointment that an adverse
report from him would produce In the Dis
trict of Columbia, which has paid one-half
the cost Of the work and has nearly re-
covered from the effects Of the report of
the commission of experts of 1899 and now
hopes and trusts that the tunnel will be
success after all. do not see how it was
possible for Major Knight to SO thoroughly
convince himself that there are and will
be no dangers of accidents which could
rot be properly guarded against during the
completion of the work. and then come to
the extraordinary conclusion found at the
end of his report.
He first says in effect that there is no
danger of accidents, and then condemns
the tunnel because If any occur repairs
would be difficult and require much time
His condemnation is founded on nothing
tn ha 1tcnn I,;. IT,,
the facts stated by him and all his de1uc-
tlons from the facts are against his con-
cluson. He acknowledges that the posi-
bllity OF the necessity Of repairs Is both
small and remote yet in spite Of this he
condemns the tunnel and suggests a plan
of his own. which, from his own figures,
would cost rearly half a million dollars
more than mis- estimated cost Of completing
in thorough manner the acqueduct tunnel,
and which would not have one-third Of its
capacity for carrying water to the Howard
University reservoir
Muj.~ Knight'. Plan.
THE plan proposed by him is a conduit
from tie distributing reservoir to the west
side of Rock creek, and thence the water is
to be carried by three 4S-inch mains to the
Howard University reservoir. In respect Of
the comparative cost of completing the
aqueduct tunnel and the plan proposed BY
Maj. knight, have this to remark: His cs-
innate of the cost of completing the tunnel
| IS 81 ,2:}3.32S. His estimate of the cost of his
plan, which is, west of Rock creek mainly
In tunneP Che proposes to substitute one
tunnel for another), is 81 iO3, 209, difference
in favoi of completing the aqueduct tunnel
of about s2I0O0O but his estimate provides
for only three 4S-inch mains.
1--WE find that Maj. knights proposed sys-
tenn would cost nearly half million of dol
lars more than the completion of the tun-
mel, while the capacity of the rev line of
works proposed by him is not one-third Of
the capacity Of the tunnel
The Danger of Accidents.
"Of the dangers of accidents to aqueduct
tunnels generally, mentioned by him, the
only one worth idering in the case of
our aqueduct tunnel is the danger of OBJ
structions of the waterway by falls of rock
from the roof. In the portions of the tunnel
yet unlined this danger is to be guarded
against by the completion of the brick
| lining, solidly backed by rubblestone or by
concrete. That this danger will then not
exist in these portions, aggregating about
cne-fourth of the length of the tunnel or in
the three-fourths in which the lining was
fraudulently done and the defects are to be
made good. is shown by the following fact:
when Maj Knight emptied the tunnel
all parts of it below line 81 feet above its
lewest point had been under water for about
| six years and half and the other parts ex-
posed to air and seepage water during the
same time During this long period the
seams of the rock of the roof Of the tunnel
had been softened and the rock had been
Iut in condition that without doubt per-
mitted all of it to fall that could fall or
would ever fall, and yet it was found that
the three miles OF lining (abouD had per
fectly filled its main object: that is to saw.
it stopped and prevented from falling into
the waterway. and without any injury to
itself all masses Of rock that NAV have
been detached from the roof of the tunnel
during the six years that it was full of
water, and, what Is more important, at the
time the tunnel was emptied last July.
where the tunnel has been completed as
was originally contemplated-that is to saw
where the spaces between the arched lin
ing and the rock roof have been solidly filed
with rubblestone masonry or with concrete,
the arched lining can never again be SUBJ
jected to shocks. There may be at some
places exterior pressures but none that the
arch will not be able to Withstand.
Twelve Days Supply Possible.
"In regard to time for repairs in case of
accidents, although I agree with Major
knight in thinking that it is most i'm
! probable that any viii occur l NAV remarI,
that the capacity of the two western reser-
voirs is about 34O00o00O gallons, of which.
as Major Knight correctly says about 300
100000 gallons are available. The CAPACITY
of the Howard University reservoir is roo
| 00000o gallons. making 100000, 900 gallons
that will be available in the three reser-
voirs. Without taking into account the dali
dent to the tunnel could interfere with. this
amount of water is equal to about twelve
days supply, and much more in case of an
accident for the use of water would then
be restricted by the Commissioners of the
District as Is now done in times of low
water in the Potomac.
Major knights estimate of the time that
would be required to empty the tunnel is
about five days. Therefore taking into
consideration only the amount of water
stored in the reservoirs. and not considering
at all the constant replenishing from Great
Falls of the water drawn from the two
western reservoirs. there would be seven
days Owenty-one days of eight hours) for
repairs; ard think it improbable that
there would be any suffering for want of
water in the city during a repair TO the fun
mel in the improbable even of an accident
to it, although there may be diminished
pressures in the areas that will depend ON
the Howard University reservoir"
Gen. MciGs' APPROVAL.
Col Elliot appends to his opinion n let
ter written to him in 1891 by the late Gen.
NJ. c. Meigs, in reference to a report made
by Col. Elliot on the water supply. Gen.
Meigs said: Il also note that YOU were
making arrangements to measure the daily
outflow of water from the unfortunate tun
mel, SO badly managed in construction and
so foolisbly, 1t seems to me, abandoned.
So many small streams descend into nat