bank of the Hudson and the first work of peculiar interest is the
Aqueduct bridge over the road from Tarrytown to Sing-Sing; before
it reaches this place it passes through three tunnels, over high
foundation walls, and encounters deep excavations.
[Illustration: XIV
_F. B. Tower._ _W. Bennett. sc._
AQUEDUCT BRIDGE FOR ROAD WAY.]
Plate XIV. is a view of this bridge: it is eleven and a quarter miles
from the dam. The arch is 20 feet span and has a versed sine or rise of
5 feet. From this the Aqueduct passes on, encounters one tunnel, and
reaches the valley of Mill River, twelve miles and three quarters from
the dam. This River runs through Sleepy Hollow and enters the Hudson
about a mile and a half above Tarrytown. The stream is 72 feet below
the bottom of the Aqueduct, and the valley being of considerable width
required a very heavy foundation wall.
Plate XV. is a view of the _Mill River Culvert_: it is 25 feet span and
172 feet long. It is about half a mile east of the road leading from
Tarrytown to Sing-Sing, and to follow the course of the stream which
passes through it, it is three quarters of a mile to the _Old Dutch
Church_, near Tarrytown, which is well known, and familiar to every one
who has read Irving’s “Legend of Sleepy Hollow.”
There is much of the wildness and beauty of nature about this place;
the woods are standing close upon the work,--the stream which passes
through the culvert displays its whitened crests as it tears along
over the rocky bed, and utters its music until it is lost in the depth
of the forest. The wild vines will soon climb the walls and cover
them; vegetation will gather over the work until _nature_ and _art_ be
harmoniously _wedded_.
[Illustration: XV
_F. B. Tower._ _W. Bennett. sc._
CROTON AQUEDUCT AT MILL RIVER.]
From Mill River the Aqueduct passes the village of Tarrytown and
through one tunnel and over several depressions and streams, reaching
Jewell’s Brook which is seventeen and a half miles from the dam. This
stream enters the Hudson River about two miles below Tarrytown. The
distance from the mouth of the stream to the line of Aqueduct is only a
quarter of a mile.
Plate XVI. is a view of the work at Jewell’s Brook. The culvert for
the stream is 6 feet span and 148 feet long. The larger culvert for a
private road is 14 feet span and 141 feet long. The wall which supports
the Aqueduct at this valley is 50 feet high.
In this case, as in many others, the slope wall which covers the
face of the embankment has an arch turned in it over the top of the
culverts: the object of this is to prevent the direct pressure of
the wall upon the top of the parapet wall, as it would tend to displace
the coping or injure the parapet itself.
[Illustration: XVI
_F. B. Tower._ _J. W. Hill._
CROTON AQUEDUCT AT JEWELLS BROOK.]
After crossing Jewell’s Brook the Aqueduct passes along the bank of the
Hudson through the village of Dobb’s Ferry, where there is a tunnel
and a valley requiring a culvert, and continues from this place to the
village of Hastings, where there is an Aqueduct bridge over a rail-road
which is used for transporting marble from the quarry near by, to the
landing on the Hudson River.
Plate XVII. is a view of this bridge and the view under the arch shows
the face of the quarry which is near the work; the landing at the river
is near by, giving a very rapid descent from the quarry. The arch has a
span of 16 feet and a rise of 1½ foot. This bridge is twenty-one miles
from the dam.
From Hastings the Aqueduct continues along the bank of the Hudson until
it reaches the village of Yonkers where it leaves the valley of the
Hudson, and passing through a tunnel of considerable length reaches the
valley of Saw-Mill River. At the crossing of this valley there is a
culvert of 20 feet span for a public road to pass under the Aqueduct,
and one having two arches each 25 feet span for the river.
Plate XVIII. is a view of the work at Saw Mill River.
The water is set back at this place by a dam for a mill a short
distance below, giving the stream an appearance of more magnitude than
it really possesses. This point is 25 miles from the dam. The wall
which supports the Aqueduct over this valley is 40 feet high.
From Saw-Mill River the Aqueduct passing through one tunnel soon
reaches Tibbit’s Brook, which it crosses by means of a foundation
wall about 30 feet high and a culvert of 6 feet span, and continues
along the south side of the valley of this brook, thence to the Harlem
River which it crosses at one mile from McComb’s Dam. This crossing is
thirty-three miles from the Croton Dam, and about ten miles from the
City-Hall.
The distance across this valley is about a quarter of a mile, and the
surface of the River is 120 feet below the bottom of the Aqueduct.
In all the examinations which were made with a view of bringing
water from Westchester County, the crossing of this River, or _arm
of the sea_, was regarded as the most formidable work that would be
encountered; various plans were proposed, and in presenting these plans
the project was such as to call into requisition much talent and skill.
An Aqueduct Bridge built of stone, having arches resting upon piers and
abutments, was proposed so as to continue the Aqueduct across with its
regular inclination.
An Inverted Syphon of iron pipes was proposed; the pipes to descend to
a level near the surface of the River, and passing along upon a stone
embankment rise again and connect with the Aqueduct: in this stone
embankment an arch was to be built of sufficient dimensions to allow
free passage of the water of the River.
[Illustration: XVII
_F. B. Tower._ _J. W. Hill._
CROTON AQUEDUCT AT HASTINGS.]
Another plan was proposed which, though novel in its application
to such purpose, was worthy of consideration: this was to build a
Suspension Bridge of wire cables reaching across the valley, supported
at intervals upon suitable stone piers. This, maintaining the regular
inclination of the Aqueduct, would support iron pipes. The design
was a bold one, yet instances where such bridges have been constructed
for road-ways afford examples of the feasibility and permanency of the
structures, and prove that the application of that principle for this
purpose was not a visionary project.
The plan which was adopted as the most suitable under all the
considerations of economy and security to the work, was a _Low Bridge_
to support an inverted syphon of iron pipes; and the design of it was
as follows: adjacent to the southern shore of the river there was to
be constructed an arch for the channel of the river, of 80 feet span
and springing from abutments 10 feet above high water level; this would
form a passage of 80 feet wide, and the height from high water level
to the under side of the arch at the crown would be 50 feet: south of
this arch followed three other arches on the slope of the rocky hill,
of 35, 30, and 25 feet span: south of these arches a foundation wall
was designed to continue the plane of inclination to the level of the
Aqueduct. From the large arch to the northern shore of the river an
embankment of stone was designed for the support of the pipes, and from
this wall the table land on the northern shore and the slope of the
northern side of the valley, would be excavated to a form to give the
proper position to the pipes descending from the Aqueduct. The lowest
level of the top of this stone embankment was designed to be 4 feet
above flood tide. Suitable parapet walls were designed to be built
along the sides of the embankment to sustain a covering of earth over
the pipes. With the form which was given to this _inverted syphon_,
four pipes, each of 3 feet interior diameter, were found to give a
discharge of water equal to that of the Aqueduct of masonry on the
established inclination.
In accordance with this plan of the _Low Bridge_ the work for
crossing the River was put under contract and some progress made in
its execution, when a law was passed by the Legislature of the State
requiring, instead of this, a structure, the arches of which should
be (over the channel of the river) at least 80 feet span and having a
distance of 100 feet from the level of high water to the under side of
the crown; or to go under the channel of the river by a structure which
should not rise above the bed, and that would leave the present channel
unobstructed. At this time when the work was going on vigorously,
they were compelled to abandon the plan which had been adopted, and
devise one which would comply with the requirements of the law of the
Legislature. A comparison was instituted between the plan of a tunnel
under the bed of the river and that of a bridge of masonry at the
required height above the river.
The tunnel would be at least 300 feet long and the top of the masonry
forming it, would be 18 feet below high water level. In this tunnel the
iron pipes would pass under the River and would be protected from the
salt water.
[Illustration: XVIII
_F. B. Tower._ _W. Bennett. sc._
CROTON AQUEDUCT AT YONKERS.]
An estimate of the cost of crossing by means of each plan was made,
and the result was in favor of the tunnel under the bed of the River;
but from the imperfect knowledge which could at best be obtained of
the formation of the bed, there was great uncertainty in the estimate
of the cost of the tunnel and the time that would be required for its
completion. The history of the progress of work in the tunnel under the
Thames at London warned them of the difficulties of such a work and
the uncertainty of arriving at a proper estimate of the cost.
In the alternative to which they were driven by the Act of the
Legislature, the plan of an Aqueduct bridge of masonry was adopted as
the proper one for crossing the River; but in establishing its altitude
they complied _only_ with the requisitions of the law, and made the
soffit or under side of the arches at the crown, 100 feet above common
high water level. This would not carry the work up to the level of the
Aqueduct, and would render it necessary to connect the Aqueduct on
each side of the valley by iron pipes which would descend to the level
of the bridge and crossing it rise again to the masonry channel-way.
The plans which were before spoken of for a bridge of masonry across
this valley, contemplated a structure which would maintain the regular
inclination of the Aqueduct; and the channel-way would have been formed
of masonry having a cast iron lining; but a more full consideration
of the subject suggested the propriety of using iron pipes over
the bridge, even if it had been carried up to the grade plane of
the Aqueduct: when the use of iron pipes was determined upon, then
considerations of economy induced them to build the work _only_ high
enough to comply with the requirements of the law.
The plan which has been adopted for building an Aqueduct bridge across
this valley is as follows: on the south shore of the river there is one
arch of 50 feet span, across the river there are eight arches, each of
80 feet span, and on the north shore there are six arches each of 50
feet span; making a range of fifteen arches. From the extremes of this
range of arches, a foundation wall of dry stone work connects with the
Aqueduct.
Two of the piers in the river have a rock foundation and the
foundations for those where rock is not obtained is formed by driving
piles which are placed 2½ feet from centre to centre, and the spaces
between filled with concrete to a depth of 3 feet below the top of them.
Plate XIX. is a view of this bridge, which, when completed, will be
the most interesting work on the whole line of Aqueduct, and in its
appearance will rival the grandeur of similar works of the Ancient
Romans. The height from the foundations in the river, to the top of the
work is 150 feet; the width across the top is 21 feet. The pipes when
laid upon the bridge will be covered with earth to protect them from
frost. The distance between the extremes of the pipes when laid across
the bridge will be 1377⅓ feet. For a distance of 18 feet at each end
of the pipes there is an inclination and the remainder of the distance
across, which is 1341⅓ feet, they are level.
The bottom of the interior of the pipes on the level part, is 12-8/10
feet below the bottom of water way of the Aqueduct on the north side,
and 10-5/10 below that on the south side of the valley.
In the progress of excavating in one of the coffer dams in the
channel of the river a portion of a sunken vessel was found within
the enclosure; it had the appearance of great age. Tradition among
the inhabitants of the vicinity says that at an early period of the
Revolutionary war a vessel was scuttled and sunk in that part of the
river.
[Illustration: XIX
F. B. Tower. Napoleon Gimbrede. sc.
CROTON AQUEDUCT AT HARLEM RIVER.]
To a mind fond of antiquarian researches and accustomed to invest
objects of such a nature with associations of the past, this ancient
wreck would furnish a fruitful theme. We are now laying the foundation
of a magnificent work: at the day when this vessel was sunk the
American people were laying the foundation of a new form of government
composed of principles which should support a fabric of enduring
strength and beauty. We are now building a work which will stand as
a monument of the genius and enterprise of the age, but it may be
regarded among the fruits of that civil and religious liberty which has
been reared upon the foundations formed by the people of that day.
The water is now conveyed across this valley by an iron pipe of 3 feet
interior diameter. In the progress of preparing foundations for the
piers of the bridge, an embankment has been formed across the River and
the pipe leaving the Aqueduct on the north side of the valley follows
down the slope of the hill, and crossing over the River upon this
embankment, ascends on the south side again to the Aqueduct. At the
bottom or lowest point in this pipe, a branch pipe of 1 foot diameter
has been connected, extending a distance of 80 feet from it at right
angles and horizontally: the end of this pipe is turned upwards to form
a jet, and iron plates are fastened upon it giving any form that may be
desired to the water issuing. The level of this branch pipe is about
120 feet below the bottom of the Aqueduct on the north side of the
valley; affording an opportunity for a beautiful _jet d’eau_;--such an
one as cannot be obtained at the fountains in the city. From an orifice
of seven inches diameter the column of water rises to a height of 115
feet when there is only a depth of 2 feet of water in the Aqueduct.
To those who had watched over the work during its construction and
looked for its successful operation, this was peculiarly gratifying. To
see the water leap from this opening and rise upwards with such force
and beauty, occasioned pleasing emotions and gave proof that the design
and construction of the work were alike faultless, and that all the
fondest hopes of its projectors would be realized.
The scenery around this fountain added much to its beauty; there it
stood,--a whitened column rising from the river, erect, or shifting its
form, or waving like a forest tree as the winds swayed it, with the
rainbow tints resting upon its spray, while on either side the wooded
hills arose to rival its height: all around was of _nature_; no marble
basin,--no allegorical figures, wrought with exquisite touches of _art_
to lure the eye, but a fountain where nature had adorned the place with
the grandeur and beauty of her rude hills and mountain scenery.
Plate XX. is a distant view of the jet at Harlem River.
From Harlem River the Aqueduct passes along the south bank of the River
for a short distance where it rests in the side of the rocky hill, and
continues over an uneven surface encountering two tunnels before it
reaches Manhattan Valley, which is about 35 miles from the Croton dam.
This valley is four fifths of a mile wide where the Aqueduct meets it,
and the depression is 102 feet below the plane of Aqueduct grade.
[Illustration: XX
_F. B. Tower._ _W. Bennett._
VIEW OF THE JET AT HARLEM RIVER.]
Here was an opportunity for constructing a work of architectural beauty
and boldness by building up with arcades of arches, one line above
another, and thus maintain the regular inclination of the Aqueduct;
but considerations of economy forbade it. Where the Aqueduct reaches
the north side of the valley, a gate chamber is formed, and from
this, two pipes of 3 feet interior diameter descend to the bottom of
the valley and ascend on the south side to another gate chamber where
they connect with the Aqueduct again. Provision is made for four pipes
of 3 feet diameter, but at present only two are laid which answer the
demands of the city at this time. At the bottom of the valley waste
cocks are provided which discharge into a sewer leading to the Hudson
River, a distance of half a mile.
The lowest point in the pipes is 102 feet below the bottom of the water
way of the Aqueduct on the north side of the valley.
From Manhattan Valley the Aqueduct passes through a tunnel, and
following its course the next work of interest is at Clendinning
Valley, which is thirty-seven miles from the Croton Dam. This valley is
1900 feet across, and the Aqueduct is supported upon a foundation wall
of dry stone work having the face laid in mortar, except over three
streets where bridges are built, having an arch of 30 feet span for the
carriage-way and one on each side of 10½ feet span for the side walks.
These bridges are over 98th, 99th, and 100th streets.
[Illustration: XXI
_F. B. Tower._ _W. Bennett. sc._
CROTON AQUEDUCT AT CLENDINNING VALLEY.]
Plate XXI. is a view of a portion of the work at Clendinning Valley
showing the three bridges; and comprises a length of about 700 feet.
The greatest height from the foundation to the top of the work is 50
feet, and the width at the bottom of the Aqueduct is 30 feet. Parapet
walls are built on the sides of the wall above the bottom of the
Aqueduct to support a covering of earth over it.
Plate XXII. is an enlarged view of one of the bridges and a portion of
the foundation wall and Aqueduct adjacent to it. The Aqueduct has a
cast iron lining over the bridges like that described at the Sing Sing
Kill.
These bridges are beautiful specimens of mechanical work; indeed the
whole structure across this valley has a degree of neatness, finish,
and taste, not surpassed by any on the line of Aqueduct.
To visit this structure and follow along its whole extent, gives one
an idea of the magnitude of the work which the City of New-York has
accomplished; particularly when it is considered that this is only one
of the _parts_ which make up the _whole_.
From Clendinning Valley the Aqueduct soon reaches the Receiving
Reservoir which is thirty-eight miles from the Croton Dam.
This Reservoir occupies an elevated part of the island between 79th
and 86th streets and between the 6th and 7th Avenues. It covers seven
of the city blocks; is divided into two divisions, one covering three
and the other four of these blocks. It is 1826 feet long and 836 feet
wide from outside to outside of the top of the exterior walls of the
embankment, making an area of thirty-five acres.
[Illustration: XXII
_F. B. Tower._ _Gimber._
AQUEDUCT BRIDGE AT CLENDINNING VALLEY.]
The situation was chosen as one affording the proper elevation: but its
formation was such as to present difficulties in the way of making the
Reservoir perfectly water-tight; the surface, in tracing it from 79th
to 86th street, was quite undulating, a portion of it in the southern
division of the Reservoir falling below the proposed bottom, and that
portion of the surface which was earth, forming only a covering to
the rock, which over the whole island, presents a singularly broken and
uneven formation. In almost every instance of excavation, the rock was
found above the proposed bottom of the Reservoir, and the difficulty
of preventing leakage along the surface of this rock may easily be
conceived; but considering that measures are taken to prevent such an
occurrence, another difficulty is still presented in the formation of
the rock: the veins and fissures which are frequent in this gneiss
formation would possibly afford courses for the water to escape; the
rock being unsound in many instances, would render such an occurrence
still more liable. A Reservoir has however, been constructed here which
proved, when it was filled with water, that sufficient precaution was
used to prevent leakage, and that the difficulties which presented
themselves before the commencement of the work were no longer to be
feared.
The embankments forming the Reservoir are made of good assorted earth,
and a portion of the bank is puddled, or made compact and impervious by
wetting the earth and using a spade to force it into a compact state.
They are about 20 feet wide on the top, and increase in thickness
towards the base by a slope on both sides: the outside face of the
Reservoir bank has a slope of 1 foot horizontal to 3 feet vertical:
the inside has a slope of 1½ foot horizontal to 1 foot vertical. The
outside face is protected by a stone wall 4 feet thick having the face
laid in mortar: the inside face is protected by a slope wall of stone
laid without mortar, 1¼ foot thick. The top of the bank is 4 feet above
top water line, and the inside slope wall terminates at 2 feet above
top water line, leaving the remainder of the face to be covered with
grass, so as to present a belt of green above the water on the bank
entirely around the Reservoir.
A neat fence bounds the outside and the inside of the top bank, forming
a walk of a mile in length around the entire Reservoir.
The greatest depth of water in the northern division is 20 feet: it was
originally intended to excavate so as to give the water a depth of 20
feet over the whole, but a quantity of rock was left, as the capacity
was thought to be sufficient without taking it out.
The southern division has 30 feet of water where the bottom was filled
in with embankment, and 25 where excavation was made. A portion of rock
was left in this division for the same reason as that in the northern
division; the greater part of it being in the south-west corner, where
it rises above top water line.
The capacity of the Reservoir when both divisions are full, is
150,000,000 Imperial gallons.
The surface of water in the northern division covers 18.13 acres, and
in the southern division, 12.75 acres; making in both nearly 31 acres.
Plate XXIII. is a plan of the Receiving Reservoir.
The Aqueduct enters a gate chamber at A. where there are regulating
gates by which the water can be discharged into the northern division;
or into the southern division by a continuation of the Aqueduct within
the Reservoir bank to the angle B. of that division.
[Illustration: XXIII
Scale 200 feet to one inch
_F. B. Tower._ _Gimber._
RECEIVING RESERVOIR]
A connection pipe of cast iron is placed in the division bank at C. to
allow the water to flow from one division into the other in order to
equalize the level; it is placed 10 feet below top water line and has a
stop-cock to close or open it.
At D. is a waste weir, where surplus water may pass off: it is so
arranged that the water, when it rises to a proper level, will flow
into a well, and from this a brick sewer conducts it off into low
grounds, where it finds its way to the East River.
At each place where it is designed to discharge water from the
Reservoir, a gate house is built far enough into it to reach the
greatest depth of water beyond the slope of the embankment. These
houses have a wall upon three sides, and the front which faces the
centre of the Reservoir has a suitable screen of wood work and wooden
gates which regulate the level below the surface for the current
of discharge, and the iron pipes leading from these houses have a
stop-cock by which the discharge is controlled; this stop-cock is in a
vault within the Reservoir bank.
The position of these effluent gate houses is marked on the plan by the
letters E, F, G, H, there being two in each division. A foot bridge
affords convenient access from the bank to the house.
Those houses on the east side denoted by E, F, are the ones from which
pipes lead to the lower or Distributing Reservoir, and those on the
west side denoted by G, H, are intended for supplying the western part
of the city north of the Distributing Reservoir.