The Water System of the City of New York
The water consumption in Greater New York, consisting of the five boroughs, is as present nearly 555,000,000 gallons daily from all sources and the estimated population is 5,800,000 exclusive of 400,0000 commuters and other transients. The Department of Water Supply, Gas and Electricity, of which William Williams is commissioner, has jurisdiction over the collecton, transportation, pumping, distribution, and collection of revenues for the municipal water supply and supervisory control over the private water companies. The construction of the Catskill system is under a separate city organization, designated as the Board of Water Supply. New York City at present obtains most of its water from the Croton and Bronx water sheds in Westchester, Putnam and Dutchess Counties and the Ridgewood watershed in Nassau County. The total income from the sale of water amounts to approximately $13,000,000 and the operating expenses per year to about $4,000,000. The daily consumption in the two boroughs was placed at approximately 350,000,000 gallons, while about 150,000,000 gallons is the daily consumption from municipal and private sources in Brooklyn. In Queens the daily consumption averaged 34,000,000 gallons, while the figure for Staten Island, which is the Borough of Richmond, was about 11,500,000 gallons.
Before the introduction of the Croton water supply in 1842 the city (Borough of Manhattan) had no general supply system, being supplied mainly from wells and cisterns. The Manhattan Water Company, later the Manhattan Bank, had, since about 1800, distributed through a system of hollow logs a small quantity of water drawn from wells. The original Croton system with addition of two storage reservoirs, was sufficient until about 1880. Danger of shortage due to inadequate aqueduct capacity resulted in construction of a new aqueduct between 1885 and 1893. The commission for this work also undertook construction of additional storage reservoirs as required and the last of these to be undertaken was Croton Falls which was completed in 1911. The available storage in the city was increased in 1862 by the new Central Park reservoir, the largest of the three Central Park basins.
Manhattan and Bronx.
The boroughs of Manhattan and The Bronx are practically supplied by the same sources and the gravity mode, water being pumped to high sections. The high pressure in lower Manhattan and part of Brooklyn being exclusively for fire protection purposes, and is connected with the regular distribution mains and provision made for the use of salt water in case of mergency. Manhattan and The Bronx were supplied by the Croton and the Bronx and Byram watershed. Croton watershed covers an area of 360 square miles, while that of The Bronx and Byram covers 22 square miles. Croton was used entirely for Manhattan and one-half of The Bronx population supplied with Croton and the other by Bronx and Byram. There are two high pressure system pumping stations in Manhattan, each of which is equipped with six electrically driven centrifugal pumps. Each was connected with the Croton supply and in addition one with the North or Hudson River and the other with the East River, these pumping stations responding to every alarm with a pressure of 125 pounds per square inch. Included in the distribution system are something like 108 miles of mains, from eight to twenty-four inches in diameter apd over two thousand four-nozzle hydrants. The use of a system of telephones enables the increase or decrease of the pressure at any point. The water supply for the Borough of Manhattan is obtained wholly from the Croton River, which lies some twenty-two miles north of the city line, and enters the Hudson River from the east just above the City of Ossining. The large masonry dam which is built across the valley about three miles from the point where the river enters the Hudson is known as the New Croton dam. Above this dam there is a watershed area of 360 square miles, containing a population of about 25,000, mainly concentrated in several small towns and villages. The property holdings of the city in the watershed amount to about 30 square miles. The watershed is divided into twenty-six sanitary patrol districts. In addition, sewage-treatment plants are operated by the city for the Villages of Mount Kisco and Brewster, and chlorinating plants are placed on four of the streams where there is most danger from pollution. Chemists and bacteriologists are at the two laboratories operated by the department, examining the water furnished from the Croton River and all other sources. As the flow of Croton River varies, the city has twelve reservoirs including the old Croton reservoir, which have a total capacity of 104,000 million gallons. The main reservoir is Croton Lake formed by the new Croton Dam. The other reservoirs and ponds are utilized to maintain the required volume of water in Croton Lake. In addition to the regular distribution system. a high-pressure fire service system has been installed, covering the west side of Madison and Fourth avenues below 34th street and the east side of Third avenue below Houston street. Two pumping stations, one near the Hudson River at Ganesvoort street, and one near the East River at Oliver street, deliver water at any pressure required by the Fire Department, up to 300 pounds per square inch, obtaining the supply normally from the Croton mains, but having emergency connections so that the salt water from the river can be utilized. The mains, valves and hydrants connected with this system are designed so that the water can be delivered from the pumping stations directly to the hydrant, at full pressure. The low service is supplied by Croton delivered by gravity. The supply for intermediate service is supplemented by pumping water at the Jerome Park pumping station, and at the same station is pumped the supply for the high service. In The Bronx the Bronx system was developed in 1894, and the Byram River was added in 1897. The Jerome Park reservoir was put into use in 1906.
In Brooklyn wells and cisterns were the only source of supply prior to 1859 when water collected on the south side of Long Island was delivered into the distribution system. The original works extended east to th« Hempstead Valley and additions were made from time to time. Between 1889 and 1892 the extension to Massapequa was made and at this time the Ridgewood south side pumping station was constructed. Brooklyn is equipped with two high pressure fire service systems. One is for the purpose of protecting the business and manufacturing districts and the other is for the Coney Island amusement section. There are a main and a reserve station for the supply for the business and manufacturing districts. Both of these are supplied from the Ridgewood mains while the main station is also connected to the East River. Each of these stations has electrically operated pumps and both together have a rated capacity of 24,000 gallons per minute against a pressure of 300 pounds per square inch. The pumping station that is for the Coney Island system has pumps driven by gas engines and the total capacity is 4,500 gallons per minute against 300 pounds per square inch pressure.
In the Borough of Queens the first ward is supplied from Brooklyn system supplemented by water from the municipal pumping stations in the third ward, Queens. The third ward is supplied by two pumping stations, one station drawing its supply entirely from driven wells and the other obtaining approximately half its supply from a small lake, the water being filtered. The Second, Fourth and Fifth wards are supplied by private water companies. There are four of these private water companies, with two others serving special customers.
The Borough of Richmond is dependent for its supply on ground water drawn from wells, the city owning and operating six small plants. The largest plant, known as the Southfield Boulevard development, was put in operation in 1915 and consists of four auxiliary driven-well units, using electrically-driven centrifugal pumps to collect the supply and deliver it to the main station where a fifth well group is located. At the main station, steam pumps deliver the supply directly into the distribution system. The southwestern portion of the island is covered by the Tottenville low service, with a standpipe at an overflow elevation of 143 feet. The low service for the remainder of the island utilizes the Third Avenue reservoir. The intermediate service utilizes the Clove reservoir, but the intermediate and low service areas are inter-connected, due to location and capacity of existing pumping stations. The high service is controlled by the Grymes Hill standpipe. A private company operates a very small plant at New Dorp, supplying only about 0.1 million gallons daily.
Catskill Water Supply.
The Catskill system is under the Board of Water Supply which consists of three commissioners, Charles Strauss, Charles N. Chadwick and John F. Galvin. The four drainage areas, or watersheds, from which the new supply is to be drawn, are situated west of the Hudson River, in the Catskill Mountains. In the aggregate these watersheds have an area of nearly 900 square miles, and individually, as follows: Esopus, 255 square miles; Schoharie, 228 square miles; Rondout, 131 square miles ; Catskill creek, 163 square miles, to which can be added several small contiguous areas helping to make up the grand total. From this gathering ground it is estimated that even in a series of extraordinarily dry years 770,000,000 gallons daily can surely be drawn the year through. To collect these waters several large impounding reservoirs are to be created from time to time, and inter-ccnnected by aqueducts. Only the Esopus watershed is being developed now, but its sole reservoir, known by the Indian name of Ashokan, is by far the largest and most important of them all. From this reservoir the Catskill aqueduct will convey the water into all the five boroughs of the city. Within the city limits the aqueduct is known there as the city _____n nel. It extends to two terminal shafts in Brooklyn whence steel and iron pipe conduits continue into the Boroughs of Queens and Richmond. Although in a series of dry years the Esopus watershed cannot be depended upon to supply more than 250,000,000 gallons each day, the Catskill aqueduct has, for economic reasons, been constructed of 500,000,000 gallons daily capacity. Construction operations have been in progress about eight years. The development of the Esopus watershed is practically completed and the aqueduct to deliver this water to the five boroughs is finished except for a short length of the Narrows siphon linking Staten Island with Brooklyn. Ashokan impounding reservoir was recently storing over 40 per cent, of its capacity. Kensico storage reservoir through great rapidity in progress in construction of the Kensico dam has been essentially completed and commenced storing water last November. Hill View equalizing reservoir has been storing Catskill water since December and Silver Lake terminal reservoir is more than three quarters done.
The Ashokan Reservoir.
Ashokan reservoir, about 14 miles west of the Hudson at Kingston, was built under contracts amounting, together with the expense for relocating highways and the Ulster and Delaware railroad, to nearly $20,000,000. The Olive Bridge dam, across Esopus creek, the Beaver Kill and Hurley dikes, across smaller streams and gaps between the hills forming the natural walls of the reservoir, the Dividing dike and weir dividing the reservoir into two basins, and the Waste weir over which the surplus flood waters may safely be discharged, are the principal structures of the reservoir. Olive Bridge dam is a massive structure consisting of a central masonry portion flanked by earth dikes, or embankments, known as the North and South wings. The masonry part, founded on solid ledge-rock, is built of Cyclopean concrete with pre-cast concrete face blocks. The wings of the Olive Bridge dam and the dikes are built of selected earth spread in layers 4 or 6 inches thick and compacted by heavy rollers. Each dike has a concrete core-wall extending to ledge-rock or into very compact impervious earth foundation.
The Kensico Reservoir.
Kensico reservoir, east of the Hudson, and 30 miles from the City Hall, will contain several months’ supply of Catskill water and will act as a storage reservoir, so that the flow into the city will not he interrupted while the 75 miles of aqueduct between it and the Ashokan reservoir are being inspected, cleaned or repaired at any time. It is nearly finished under contracts amounting to approximately $8,500,000. It is on the line of the Catskill aqueduct and will be, in a more distant future, the great wholesale distributing reservoir for the metropolitan district. This reservoir is formed by the Kensico dam across the valley of The Bronx River, about three miles north cf White Plains. One mile northwest from the Kensico dam, a low gap in the hills was filled with an earth dike about 1,450 feet long, with a maximum height of 25 feet. The water will be about 110 feet deep over the surface of the old Kensico reservoir, which was developed in 1885, and will be 54 feet deep over the surface of the Rye ponds, which were auxiliary to the old Kensico reservoir and are included in the new. For the purpose of the new Kensico reservoir, 3,200 acres of land were acquired, which, in addition to the 1,300 acres acquired for the old reservoir and Rye ponds, make a total of 4,500 acres, providing a marginal protective strip around the entire flow line. Catskill water will be delivered into the Kensico reservoir at the upper end of The Bronx Valley where the normal surface of the reservoir, Elevation 355, is at the hydraulic grade line of the Catskill aqueduct. At this place there is a covered influent weir and a gate house. The water will be drawn from the reservoir through a short tunnel at a point on the west side of the reservoir about one mile above the Kensico dam. At the reservoir end of this tunnel is the Upper Effluent gate house containing sluice gates for controlling the flow from the reservoir into the aqueduct. At the lower end of the outlet tunnel is a large gate chamber in which the flow of the water will be regulated by valves and either diverted through the Kensico aerator or sent directly to the aqueduct. Near the lower gate house is the Screen chamber in which all the water will be passed through fine mesh screens before it flows on toward the Hill View reservoir. A reinforced concrete by-pass conduit, 11 feet in diameter and 11,000 feet long, from the Influent gate house at the upper end of the reservoir, connects with the Upper Effluent gate house so that water may be delivered directly to New York before the completion of the Kensico reservoir, or at any other time if it should be desirable. The Kensico dam is a gravity masonry structure of cyclopean concrete. The up-stream face is of concrete blocks. The concealed portion of the downstream face below the final grading was molded against forms, above which the remainder of this face is of cut-stone masonry. The entire dam is divided into sections by transverse expansion-joint., about 79 feet apart longitudinally. These are faced on one sine with concrete blocks forming a series of vertical tongues and grooves against which the masonry of the other side was built. Near the up-stream face a copper strip has been placed across each expansion-joint continuous from bottom to top to act as a waterstop. The contraction and expansion are caused by changes of temperature and result in slight opening and closing of the joints from season to season.
Hill View Reservoir.
Hill View reservoir is located in Yonkers. Its function is to equalize the difference between the use of water in the city as it varies and the steady flow in the aqueduct. It will hold 900.000,000 gallons of water with a depth of 36 ½ feet. It is an uncovered artificial reservoir of the earth embankment type. The reservoir is divided into two basins by a wall that contains the aqueduct so that either one or both basins may be used or be by-passed when required, or water delivered directly into the city tunnel.
Catskill Aqueduct North of City.
There are four distinct types of aqueduct, cutand-cover, grade tunnel, pressure tunnel and steel pipe siphon north of the city. The entire aqueduct to the city line, aggregating 92 miles, is completed, excepting some grading, grassing, etc., on some short stretches, completion of a few buildings, installation of some equipment, etc. The cut-and-cover type forms 55 miles of the aqueduct, is of horseshoe shape in cross section and contsructed of concrete. Where hills or mountains cross the line and it would have been impracticable or uneconomical to circumvent them, tunnels at the natural elevation of the aqueduct were driven through them. There are 24 or these grade tunnels, aggregating 14 miles. They are horseshoe shape, 17 feet high by 13 feet 4 inches wide, and lined throughout with concrete. They are on a steeper gradient than the cut-and-cover portions. Where deep and broad valleys were crossed and there was suitable rock beneath them, circular tunnels were driven deep in the rock and lined with concrete. There arc 7 pressure tunnels, totaling 17 miles, with a diameter of about 14 feet. A shaft at each extremity connects each pressure tunnel with the adjacent portions of the aqueduct, with one exception. This exception is the junction between Bryn Mawr steel-pipe siphon and Yonkers pressure tunnel: the three pipes, each 11 feet in diameter, enter the hill at an elevation 167 feet below hydraulic gradient of the aqueduct and arc sealed into the rock in three branch tunnels, which converge into the main tunnel 16 feet, 7 inches in diameter. Drainage shafts were constructed so that each tunnel can be unwatered for inspection, cleaning or repair. For the pressure tunnel under Croton lake, the Dowtitake shaft is also the Drainage shaft and contains the connection to the lake. Yonkers pressure tunnel can be drained by gravity through the Bryn Mawr steel-pipe siphon, with which it is connected. The Hudson River is crossed by means of a tunnel whotly in granite rock, at a depth of 1,114 feet below sea-level, between a shaft at Storm King Mountain on the west bank and another shaft on the east side of the river at Breakneck Mountain. The top of the West shaft is closed by a thick concrete plug, but the East shaft, which is the drainage and access shaft for the Moodna-Hudson-Breakneck pressure tunnel, as well as a waterway, required a removable cover, and for it steel castings and forgings of unusual size and shape had to be manufactured. The Drainage shaft is 14 feet in diameter, outside of which concrete is solidly packed against the rock. About 10 feet above sea-level, this shaft is covered by a steel casting nearly hemispherical in shape. This dome rests on a caststeel ring called the curb. Steep-pipe siphons were used in valleys where the rock was not sound or where for other reasons pressure tunnels would be impracticable. These steel pipes are made of plates from 7-16 inch to ¾ inch in thickness riveted together, aiid are 9 feet and 11 feet in diameter. They are lined with two inches of cement mortar, enveloped with concrete and covered with an earth embankment. There are 14 of these siphons aggregating 6 miles. Three pipes are required in each siphon for the full capacity of the aqueduct, but only one is now needed and this one pipe has been completed in all the siphons. These pipes are not true siphons but are given this name because of their approximate resemblance to an inverted siphon.
Aeration and Filtration.
In connection with the Headworks of the Catskill aqueduct, at the Ashokan reservoir, and also at the Kensico reservoir, an aerator capable of treating all the water which will flow in the aqueduct has been built and is being equipped. These two aerators are great fountain basins, approximately 500 feet long by 250 feet wide, each containing about 1,600 nozzles through which jets of water will be thrown vertically into the air. The nozzles are so designed that the water will be divided into fine spray, to permit thorough admixture of oxygen and removal of undesirable gases and other matters causing tastes and odors. Provision for a filtration plant was made by the acquisition of 315 acres of land at Eastview, near Tarrytown, close to the line of the aqueduct, and about two miles below the Kensico reservoir. Here a connection chamber was built in the aqueduct, so that water can be diverted to. and received back from, the filter plant. Pending the completion of the filters, for which studies are in progress, a small coagulating plant is being built over the aqueduct, in Pleasantville, to aid in removing turbidity from the water whenever the turbidity rises above a satisfactory limit.
The City Tunnel.
From the Hill View reservoir, Catskill water will be delivered to the five boroughs by a circular tunnel in solid rock reducing in diameter from 15 feet to 14, 13, 12 and 11 feet. The total length of the tunnel is 18 miles. From two terminal shafts in Brooklyn, steel and iron pipelines extend into Queens and Richmond. A 36inch, Hexible-jointed, cast-iron pipe, buried in a a trench in the harbor bottom, has been laid across a The Narrows to the Staten Island shore, whence a 48-inch cast-iron pipe extends to the Silver Lake reservoir, holding 435,000,000 gallons. The total length of this delivery system is over 34 miles. The city tunnel, which is the longest tunnel in the world for carrying water under pressure, or any other purpose, was constructed from 25 shafts. Through 22 of these shafts the water will be delivered into existing and additional mains. Provision is made at Shafts 11 and 21 for unwatering the tunnel, whenever necessary, for inspection, cleaning or repairs. Shaft 1 was sunk for construction purposes only and was sealed and refilled. At the top of each of the twenty-four other shafts a chamber has been constructed to contain the valves and other appliances for controlling the admission of water from Hill View reservoir, the flow and pressure of the water from the tunnel into the street mains and for the unwatering apparatus. Unusual features in connection with the operation of the tunnel are the bronze valves in the shafts, 48 inches and 72 inches in diameter, and the section valves, 60 inches in diameter, also of bronze. The former are located about 100 feet below the top of sound rock and are designed to close automatically in case of a break in the valve-chamber or in the street mains, causing an abnormally large flow of water. The section valves, two in number, are located across the main tunnel, at the foot of Shafts 13 and 18, and will permit the tunnel to be divided into parts and drained in sections without putting it entirely out of commission. Each valve will be operated by a hydraulice cylinder in the shaft-head chamber.
Silver Lake Reservoir.
The terminal reservoir for the Catskill water system, located on Staten Island, is about 2,400 feet long and 1,500 feet wide. It will hold about 435,000,000 gallons. Earth embankments close natural depressions in the ground and a dividing dike lined with concrete forms two basins. From a gate-chamber built in this dike, reinforced concrete condits extend to the boundary of the reservoir, and cast-iron pipes prolonged from them connect with the Narrows siphon and with the Staten Island service mains. Work is about three-quarters completed.