Evening star., 1896-02-22


side walls and backing.
bered. the rock has disintegrated and fall
en- into the tunnel just at the end Of the
timbfring, leaving quite a large pocket in
the roof of the tunnel. At about station
24-I-tD IN the same heading, the rock, which
IS similar in character to that at station
ESQ, has d.sintegrated, crushed through
the tagging. and filled up about two-thirfs
of the width OF the tunnel at the bottom
From Howard shaft west. AMI Foundry
Branch shaft east. for a considerable dis
tance there is quite a deposit of gravel
stone, etc, in the tunnel, which was not
there at our last report. With these ex-
ceptioas, and the increase in strength Of the
mortar due to age, we noticed no change
IN the conditions Of the tunnel now and
those existing in January, 1889"
Maj. Knights Views.
In recent report in regard to the re-
suits to be accomplished by raising the
dam at the Great Falls and completing the
tunnel conduit and reservoir, Major knight,
formerly in charge Of the WASHINGTON
aGueduct, said:
w hen the Great Falls dam ha; been
raised 2h2 feet, which work is now in prog
ress. the mouth of the conduit will be full
at low stages OF the river. The discharge of
!he conduit will increase as the water is
covered in the Dalecarlia reservoir until
the crown of the inlet of the conduit at
that reservoir is uncovered. When this is
me case, the water then will be 7.23 feet
lower than at Great Falls, and the dis
charse OF the nine-foot conduit seven
miles long, will be about 75OOO,UO gallons
IN twenty-four hours, its maximum at low
stages OF the river. This reservoir is con-
nccted with the distributing reservoir hy
l"'loo 1eet OF conduit, also nine feet in di-
ameter. Water flowing through this CON
dult must have the same rate of fall as
the nlne-foot conduit in order that the dis
charge into the distributing reservoir NOV
De at the same maximum rate of - 600 W0
gallons in twenty-four hours This reo,,ires
iaii OF OF Loo feet between the two reser-
Volrs. Inc dis tributing reservoir is con
neeted with the Howard University reser
Eolr ny the incomplete tunnel conduit
ran OF Luz rect from the distributing to
the Howard University reservoir will cor
'4,rD,ED gallons. This discharge is NOT
OF course, the maximum discharge of the
tunnel conduit. If these d;fferen = falls he
Ieuuced' the discharge will >be reduced
win the present rate of consumption the
falls may be reduced; but in eighteen vears
the consumption will at least equal and
probably exceed. the maximum discharge
given.
giving to the dam at Great Falls addition ~
height; but more permanent relief could
only be afforded by an additional conduit
from Great Falls to the Dalecarlia reser
Folr ana thence to the distributing reser-
vor. 1t will be wise precaution to con-
plete this additional conduit by 1910 and
the preliminary studies should he entered
upon Immediately. If the discharges given
are reaiiZed, they can only be at the ex-
pense OF the storage capacities of the diff
ferent reservoirs, for they correspond tn ;.
loss OF 2.I3 feet of water in the Dalecarl;a
reservoir, OF S.1S feet in the distributing
ana OF 296 feet in the new, or jointly to a
loss OF storage capacity of about 100 900 O0O
gallons. The direct result of comnletin~
the tunnel conduit would be that daijv
supply OF ABOUT 5oGonNO gallons of water
STORED fhn
reservoir ready for distribution at a nn;nt
two miles from the Capitol, while the nresN
ent distributing reservoir is four miles
therefrom. 1t is difficult to state with e~'
actness what will be the result in diffaremt
sections of the city, e''
One Objection to ComnIct,or
Maj. Knight. in his letter. presents sev-
erai possibie objections to the completion of
the tunnel and answers them all but one
This he states to be 1.-The extreme Difficulty
OF repair in case Of any accident" On this
ground he says:
IAH water above the level of the mouth
OF Rock creek shaft can readily be dis
charged INTO that creek; but the tunnel be-
low TINS level, when completed will hold
9,oplooo gallons; of this quantity only :.
Uo'Ooo can be pumped out at Rock creek
smart, with an extreme lift of about 10 feet.
II would be necessary to pump about 2
oOo.oo0 from the Champlain avenue and
east shafts, with extreme lifts of 127 and
12S feet, and 100000 from Foundry branch
smart, with maximum lift of Go feet.
About 9,oo0,00O gallons of water nust
then be taken from the tunnel at four dif
ferent shafts before the tunnel would he
open to entire inspection from end to end.
With boilers, engines and buckets of con-
siderable size this might be done in five
days. After the water had been removed
there would be ali the difficulty of repairs.
which would be occaslCned by access for
men and materials only by means of shafts
from a mile to mile and a quarter apart.
There can be no doubt that We're repairs
needed they could be executed only with
extreme difficulty.
The ordinary dangers to which tunnel
aqueduct under internal pressure is exposed
are the falling Of rock earth from the
roof, the forcing in of the sides and the
opening of cracks in the lining occasioned
by internal pressure. The first two may be
guarded against by suitable lining, includ-
ing invert; the opening of cracks in the lin
ing must be prevented by the resistance of
the rock walls exerted through solid ma
sonry backing of the lining.
1.-THE construction of the new Croton auue-
duct has proved satisfactory work of this
character to be possible, even when the orig
inal work was defective. The amount Of
defective work in that aquedSct thus made