Herald and news. [volume] (West Randolph, Vt.) 1878-1943, 1890-07-31
A GREAT WORK.
THE NEW cRoToN AaUEDUcT
AT NEW YORK.

A New York letter to the New Orleans
Picayune says that the new Crotoi
Aqueduct is the greatest work of it
kind in the world, and gives this accoun
of its construction and dimensions;
Isaac Newton, chief engineer of tn,
old aqueduct, and Benjamin S. Church
resident engineer, had the plans ready
| Tho estimates were as follows: Quaker
bridge dam and reservoir, "a, coo, 900
140, 81 feet of aqueduct from dam tc
Harlem River, 80, Ais, $50; 1890 feet of
tunnel across Harlem River, $232, 900
IL, 986 feet of aqueduct from Harlem
River to Manhattan valley, $500, 300
1000 feet Of iron siphons across Manhat-
tan valley, 1914, 900; gate house con-
nected with siphons, 100000; 9,783
feet of aqueduct from Manhattan valley
to Central park, $3.50, $50; gate house
and connection at Central park reservoir,
800, 900; waste gates between Harlem
River and dam, $50, 600; total, $14, 460,-
$40.
Benjamin S. Church was appointed
chief engineer, and hearings on the plans
began at once. 1t was finally decided
that instead of following the line Of the
old one down the Hudson valley, the new
aqueduct should have more direct in
terror course through the valleys of the
Saw Mill and Pocantico rivers, and be
built wherever practicable in horseshoe
shape, the interior dimensions of the
conduit being 1888 feet at the greatest
height and 1850 at the greatest breadth,
and affording carrying capacity of
$50, 900, 900 gallons daily, the same as a
circular conduit IA feet in diameter
The length of the line as laid out was
est miles from the Croton dam TO the
Harlem river, d miles from the eastern
shore of the river to the gatehouse at
One Hundred and Thirty-fifth street,
and "a miles from the gatehouse to the
Central park reservoir, making total Of
33t miles.
The plan was to have work on all the
sections proceed simultaneously, and TO
this end shafts were sunk at frequent in
teryals between Croton dam and the
Harlem river. The conduit was to be as
far as possible subterranean tunnel
through solid rock, whereas the old
practice it was found necessary TO line
the tunnel with brick throughout its en-
tire length, and that delayed the work
good deal. The number Of shafts sunk
was thirty eight The deepest shaft had
a depth of $50 feet and the shallowest 2S |
feet.
The completed work leaves Croton |
Lake with the bottom of the tunnel 40 |
feet above tidewater and 60 feet below
the high water level of the contemplated
Quaker Bridge reservoir. For twenty-four
miles there is fall Of 7-10ths of foot to
the mile. Then there is depression for
ITO feet of 10 feet in hundred, and the
lower level is maintained to the Harlem
River, the fall being the same as before,
cloths of foot to the mile. Because Of
he increase of pressure resulting from
he sharp decline of 10 feet in 100 it was
iecided TO reduce the size of the conduit
o ~ feet inches thence to the river, as
t could be done without impairing the
pecifed carrying capacity.
The average depth Of the tunnel below
he surface is 10 feet 1t is at the sur
ace where it crosses the Pocantico river,
icing on a level with the river bed. and
t Tibbett's brook At these points
'atehouses and waste weirs for drainage
ave been built. At Ardsley there is
ear enough approach to the surface for
mother waste gate, the discharge being
arried of in an open cut. At High
ridge there is fourth free discharge
trough an adit tunnel far beneath the
urface into the Harlem river.
In the course of construction serious
itficulties had to be overcome at two
oints. Gould's swamp, n lr Tarrytown,
lied the valley directly in the line, and
! the level of the conduit. 1t was about
J wide as the Harlem river and was
sgular swamp Of wet muck and clay !
overed with timber. At depth of 35
yet solid rock was found, and through
lis the tunnel was run under the swamp
a the inverted siphon principle.
South of Saw Mill river a very treach-
Gus strata of limerick was struck, with 4
isures filled with red clay and water Z
lat formed a quicksand. Work was I
slsyed at this point nearly year. The \
'sures in the rock extended upward $50 a
" 70 the surlhce, anu the Qu1cksand
led the tunnel as fast as it could be q
'ened. II was thought that a change :
course could not be avoided, but at c
st two extra shafts were sunk, and by a
seping the brickwork close to the head n
gs the engineers triumphed. +
The Harlem river is crossed by an in \
'rted siphon, like Gould's swamp. 1t q
as supposed that depression Of 152 o
ct below mean high tide would be o
fficient, but at that depth assure was i,
und in the rock underlying the river, i
ID the tunnel had to be carried 1856 feet I
rther down. There the rock was so 3
lid that not a particle of water pene- n
TED as it was being pierced. The o
lhon tunnel under the river is Z perfect I
role 10i feet in diameter. The pressure p
so great that the reduction of size will !,
t diminish the flow of water. h
On the south side Of the river the con- a,
1T, restored in size to 10 feet inches. +,
lrts on its former level and runs to the !
tehouse at One Hundred and Thirty
tn street and Convent avenue. At the
tehouse its floor is IS feet below the
IL