CHAPTER V. THE MAINTENANCE AND EXTENSION OF THE WATER-SUPPLY BY THE AN Act to reorganize the Local Government of the City of New York (chapter 137 of the Laws of 1870), passed by the Legislature in April 1870, created the Department of Public Works which superseded the Croton Aqueduct Department and the Street Department. The new Department was organized into the following bureaus, viz.: The Bureau of the Water Purveyor. The Bureau of the Water Register. The Bureau of the Chief Engineer of the Croton Aqueduct. The Bureau of Street Improvements. The Bureau of Lamps and Gas. The Bureau of Repairs and Supplies. The Bureau of Streets and Roads. The Bureau of the Collector of Assessments. The Bureau of Sewers. Chapter 574 of the Laws of 1871 added to the above: The Bureau of Incumbrances. The extensive and important responsibilities entrusted to the Department of Public Works were as follows: Ist. The maintenance and extension of the water-works. 2d. The maintenance and extension of sewers and drains. 3d. The collection of the water revenues. 4th. The opening of new streets and roads. 7th. The control of the street vaults. 9th. The filling up of sunken lots. 10th. The removal of incumbrances. 11th. The construction and care of the wells. All this important work was put in the charge of one Commissioner of Public Works, who was to have complete control over all the employés of the Department. The Commissioner was to be appointed by the Mayor. The first person who filled this responsible position was William M. Tweed. The names of his successors, as also those of the principal engineers in charge of the water works are given in the following table: COMMISSIONERS OF PUBLIC WORKS AND ENGINEERS IN CHARGE OF THE WATER-WORKS The only part of the work controlled by the Department of Public Works which we shall describe is the Maintenance and Extension of the Water-works. The Croton Aqueduct.-When the construction of the Croton Aqueduct was commenced in 1837, an allowance of 22 imperial gallons per capita per day, based upon the consumption in European cities, was considered ample. The population of the city of New York was, at that time, about 300,000. In giving the Croton Aqueduct a capacity of 60,000,000 imperial gallons (equal to about 72,000,000 U. S. gallons) the constructors of this work thought that they had provided for the wants of the city for many years to come. As has been stated on page 64, the waste of water became so great, soon after its introduction in the city, that it amounted in 1850, at times, to 90 U. S. gallons per capita per day. Aside from this waste, the natural growth of New York was so much greater than what had been anticipated, that twenty-five years after the Croton water had been introduced the aqueduct was delivering what had been calculated to be its maximum discharge (about 72,000,000 U. S. gallons per twenty-four hours). The rapid increase of the consumption of water is shown by the table on page 107. As the demands for water grew larger the aqueduct was made to deliver more than the quantity given above as its maximum discharge. Two circumstances made this possible: Ist. The maximum flow of 72,000,000 U. S. gallons per twenty-four hours was calculated on the supposition that the water was to be kept below the spring-line of the arch, which had not been designed to withstand any pressure from within. 2d. The maximum discharge stated had been calculated by the hydraulic formulæ based upon experiments on small pipes, which have since been found to underestimate the discharge of a large conduit. The necessity of delivering more water into the city obliged the Department of Public Works to increase the depth of the water flowing in the aqueduct, until it reached within a foot of the crown of the arch. Parts of the conduit which had settled on embankments 3 to 13 inches were thus placed entirely under pressure. The maximum capacity of the aqueduct, when filled nearly to the crown, has been variously estimated in different reports of the Department of Public Works at 90,000,000 to 120,000,000 U. S. gallons in twenty-four hours. As the consequences had been disastrous. when the aqueduct was forced to discharge 103,000,000 gallons daily, Chief Engineer Newton gave in 1881 the maximum safe discharge of the aqueduct at 95,000,000 gallons in twenty-four hours, which was based upon a depth of water of 7'5" in the conduit, the surface of the water being 12 inches below the crown of the arch, where the aqueduct had not settled below grade. In order to enable the masonry conduit to resist the additional strain to which it was subjected, by carrying a greater depth of water than what had been originally intended, it was strengthened in the following manner: The arch was uncovered and reinforced by one additional ring of brick (making the total thickness of the arch twelve inches). In some places the thickness of the arch was increased to 16-20 inches. The spandrel walls were carried up nearly to the level of the top of the arch, and retaining walls were raised correspondingly. The conduit had been originally covered with four to five feet of earth as a protection against frost. Experience having proved that two feet of earth covering was sufficient for this purpose, the earth refilling was only replaced to that depth at the crown of the arch, the surplus material being distributed on the outer slopes of the earth covering. The work of reinforcing the aqueduct as described above was commenced in 1875, and continued from year to year, to the extent the annual appropriations permitted, until all the weak parts had been strengthened. As a result of this work five inches more depth of water was permitted to flow through the aqueduct in 1889 than in 1875. While the arch was uncovered, during this reinforcement, a great many small fissures in the masonry were discovered and repaired from the outside. We have stated in Chapter IV that the Croton Aqueduct Department had frequently to stop leaks in the conduit, caused by settling of embankments. After the Department of Public Works took charge of the aqueduct this trouble increased, owing to the severe strain to which the conduit was subjected in obtaining a greater daily discharge. When the leaks were not very large, they were generally stopped by dumping sawdust, fine sand and loam, mixed with water into a paste, into the aqueduct above the leak. In ordinary cases, three barrels of sawdust mixed with 1 barrels of sand and a little cement was all the material required. About an hour's time was consumed in dropping the paste slowly into the aque duct about a mile above the leak, and three to four hours later the leakage was generally stopped by the sawdust, etc., being drawn into the cracks of the masonry by the escaping water. When the fissures to be closed were of any great extent the repairs had to be made from the inside of the aqueduct. This operation necessitated the emptying of the whole conduit whenever the repairs were near its lower end, as no provision had been made for discharging the water from only a portion of the conduit. To make repairs of two hours' duration in this manner, the aqueduct had to be shut off from the city for forty-nine hours, as it required thirty hours to empty the conduit and about seventeen to fill it again. The inconvenience caused by thus depriving the city of a two days' supply began to be seriously felt as the consumption increased. In 1881 an improvement, suggested by Mr. B. S. Church, the Resident Engineer in charge of the aqueduct, was introduced in the construction of the work, and obviated the difficulties previously experienced in making repairs from the inside. At each of the four waste-weir gate-houses (viz., at Sing Sing, Tarrytown, Yonkers, and Kingsbridge) large shutoff cross-gates were constructed. By means of these gates and the blow-off gates the part of the aqueduct between two consecutive cross-gates could be emptied independently of the other parts. This arrangement reduced the total time required for making repairs of two hours' duration from the inside to about six to ten hours. Instead of altering the existing waste-weir gate-house at Sing Sing for the cross-gates, a new building was constructed one quarter of a mile nearer Croton Lake, in order to avoid the necessity of laying a waste-weir pipe two thousand feet long. The work required in connection with the cross-gates was completed by 1886. Notwithstanding the great improvement made by the introduction of these gates, the aqueduct had occasionally to be shut off from the city for several days at a time on account of extensive repairs rendered necessary by serious breaks. On September 11, 1885, such an accident occurred near Van Courtland Station. The aqueduct had to be shut off from the city for four days for repairs, during which time the water in Central Park reservoir was lowered ten feet. The whole conduit was emptied on this occasion and several other leaks were stopped, including a large one at Dobbs Ferry, which had been running for over twenty years. On July 11, 1886, a serious break occurred on the sixth division of the aqueduct, necessitating the shutting off of the conduit from the city for three days. Whenever the aqueduct was shut off from the city the only available supply was the water stored in the three city reservoirs, the maximum capacity of which amounted only to 1,204,000,000 U. S. gallons. While the bad breaks occurred on the embankments, small fissures and cracks were discovered occasionally even where the conduit was constructed in From 1884 to 1889 the demand for water was so great that the Department of Public Works did not venture to make a thorough examination of the interior of the aqueduct. All leaks that occurred were consequently stopped from the outside. cuts. The completion of the New Croton Aqueduct in the summer of 1890 afforded at last an opportunity for a thorough inspection of the old conduit which had been in service, without a serious interruption, for nearly half a century, delivering, for the greater part of that time, much more water than had ever been intended by its constructors. Since the new aqueduct has been in use the old conduit has been thoroughly repaired from the inside, the work being done as rapidly as the annual appropriations permitted. The Storage Reservoirs. When the Department of Public Works took charge of the city's water-works in 1870, the available amount of water stored in the reservoirs was as follows: Total...... .... 1,804,000,000 U. S. gallons. The Boyd's Corners reservoir was in course of construction and not yet available. During the year 1869 an extreme drought brought the city to the verge of a waterfamine. On October 2d all the storage water mentioned above was practically exhausted and the only supply obtainable was the minimum flow of the Croton River, which had been estimated by various competent engineers between 1836 and 1842 as 32,400,000 U. S. gallons a day, above Croton Lake. The danger of part of the city being deprived of water was fortunately averted by a heavy rain-storm on October 3d. For some time previous to this event the consumption of the city had been materially reduced by the outlet-gates from the reservoirs in Central park being partially closed. The year 1870 proved to be much drier than the preceding one. In this instance a water-famine was prevented by the energetic steps taken by the Department of Public Works to increase the water-supply by purchasing the rights to draw down some of the lakes and ponds in the Croton watershed by cutting down their outlets. The additional amount of water obtained during the drought of 1870 in this manner was as follows: 70 50 600,000,000 U. S. gallons. 66 1,000,000,000 Lowered. 3 12 3 20 IO 10 66 Total.... 66 66 Water Obtained. 398,000,000 584,000,000 528,000,000 198,000,000 132,000,000 2,008,000,000 When the city stopped drawing water in this manner, dams provided with outlet-pipes and stop-planks were constructed across the outlets of some of these lakes and ponds, which, **Above the level required to discharge 36,000,000 U. S. gallons per day through the aqueduct. |