THE CROTON DAM AND JEROME PARK RESERVOIR
Progress Made on These Great Works to Date.
As the convention of the New England Waterworks association is to be held next week in New York city, a few particulars as to the water supply of the metropolis will be found interesting. It is needless to go back to the old days when wooden pipes formed the means of distribution and the old standpipe still in existence at Duane and Centre street of Aaron Burr’s and the Manhattan company’s time was the collecting medium for the waters of the Collect creek, still running under the Tombs to the North River. The need of a new source to supply the growing city was felt some years after that system had become practically useless, and the wooden reservoir (.the third built in New York), which was erected at Thirteenth street and Broadway—the supply being by pumping kept up by a steam pump—was really the beginning of the city’s system of water supply. In 1835 the Croton river was chosen as the source of supply, and the Croton aqueduct commission was formed. The old Croton aqueduct reservoir was built some forty miles from the city, with an aqueduct—a masonry conduit—leading the water thence to One-hundred and thirtyfifth street. New York. Its capacity, when running full is 90,000,000 gallons in tw-enty-four heturs; its normal daily capacity is 75,000,000. It was completed in October. From One-hundred and thirty-fifth street the water is carried in four cast iron pipes—two thirty-six-inch, one forty-eight-inch, and one sixty-inch, crossing Manhattan valley to One-hundred and nineteenth street, where is another masonry conduit extending to One-hundred and thirteenth street, whence are laid pipes to the Central Park reservoirs— the fall being 48.06 feet. Through High bridge there are three pipes—two, cast iron, three feet in diameter, and one, wrought iron, seven feet six inches in diameter. The aqueduct internally is horseshoe-shaped, eight feet wide. The area is 53.34 square feet; normal daily capacity, 75.000.000 gallons; elevation of invert at Croton lake 155.0 feet—Croton datum—grade of aqueduct one foot per mile. In 1840 was built the first storage reservoir between Seventy-ninth and Eighty-sixth streets and Sixth and Seventh avenues—now in Central Park. Its overflowings fed the late distributing reservoir in Murry Hill and Forty-second street and Fifth avenue (first used in 1842). The new masonry aqueduct was built in 1890, almost in a straight line from the Croton reservoir to the Harlem river, which it crosses by a submerged masonry conduit to the gatehouse at One-hundred and thirty-fifth street. The length of the masonry conduit is 30.87 miles; capacity 300,000,000 gallons; cost, $20^000,000. Under the Harlem the aqueduct is 311.11 feet below city datum, depth of shaft No. 25 at the south side of the Harlem river, 402.5 feet. With the old aqueduct the submerged conduit discharges into a tunnel gatehouse at One-hundred and thirty-fifth street, whence the water is carried by eight forty-eight-inch mains to the citv. As the pressure from the reservoirs falls before they are emptied, and what water is left is insufficient to reach the higher flows even of buildings of ordinary height, the construction of the Jerome Park reservoir was determined upon. The new aqueduct involved the building of the new Croton dam, now practically completed and being gradually filled till the new lake is formed. Its water surface, when filled, will be 5,000 acres, as against the 840 acres of water surface in the Central Park reservoir. its length, when full, will be nineteen miles and one-half; average width half a mile; area, including the marginal lands, acres. 1 lie length of the dam proper (on which the work began on October 1. 1892). > -3.300 feet, including 1,000 feet of spillway; breadth at base, 206 feet; height from base to crest, 297 feet; foundations extend 130 feet below bed of the river, with the spillway. It contains 850,000 cubic yards of masonry; impounds 30,000,000.000 gallons; cost about $9,000,000. A steel bridge will be built across the spillway, to connect the driveway over the crest of the dam with the road that is being built along the bluffs on the north. The same below will be graded and sodded; graveled walks will be laid out; and a large fountain will be built.
The Jerome Park the Central Park reservoir, the connection between the two being a special line of forty-eight inch pipe. It covers the area between Sedgewick and jerome avenues, the Kingsbridge road and the Misholu Parkway. Its area and that of its surroundings, is over 300 acres. I11 shape it is an irregular ellipse, and all the way round the inner line of the bottom will be about two and three-quarter miles in length. Its four-inch cement lining will cover a gently sloping surface of 250 acres. The slope of both the outer and inner wall will be 2 to 1. The inner slope is concreted and has a paving of granite blocks carried up !o two and one-half feet above high-water line, forming an embankment twenty feet wide on the top, with a vertical wall of masonry, starting from bedrock and rising above the high-water line built in the centre, rendering it water-tight. The old and the new aqueducts pass through this reservoir, whose bottom was below the old aqueduct (that is at ground level), with the new aqueduct about IOO feet below the foundation of the old. The latter foundation had, therefore, to be removed altogether and a completely new structure built in which has been incorporated a branch aqueduct from the new one. The latter is at ground level at about a mile north of the reservoir, where it begins to descend, and a tunnel carries it at a depth of sonic hundred feet below the reservoir. A vertical shaft rises from the aqueduct at the centre of the reservoir to the bottom of the latter, where this tunnel begins in the new aqueduct a gatehouse has been put in, and a surface branch has been built running parallel with the old aqueduct as far as the reservoir’s northern entrance, where the old aqueduct and the branch are imbedded in one masssive piece of masonry, built up from the solid rock of the reservoir, which, extending, from northeast to southeast, divides the latter into two separate basins. A large main gatehouse connects with the shaft by a short conduit at a point where ris*’s the shaft already alluded to as piercing the reservoir. South of that is a double conduit, each barrel of which is twelve feet in diameter. Through this the aqueducts pass, the old above the barrels at its original elevation. These con duits lead to the western and eastern basins of the reservoir at a distance of 1,500 feet south. Six lines of forty-eight-inch pipe radiate from the main central gatehouse—fine of these leading from the southeast to a high-service pumping station—with a gatehouse at each point of exit, and the main gatehouse so arranged that these mains may carry water from either basin or directly from the old or new aqueduct. In the gatehouse are contained twenty-two separate gates and many chambers with sixty huge iron gates set in dressed granite, each gate costi g $ 1.200 and weighing three tons and having 1 opening two and one-half feet wide. Gatehouses of simple construction are also placed at the outlets of the six forty-eight-inch pipes for local distribution. In a channel is laid a twenty-inch iron pipe, passing out at the Van Cortlandt valley and carrying the water drained off from each lobe f the reservoir or the chambers of the gatehouse. All round the embankment runs a watertight core wall of rock masonry, three feet thick at the top, beginning near the top of the earth above the water-line of the reservoir, extending thence to the solid rock beneath. 1 he entire length of the outer water line of the new reservoir is 14,500 feet—nearly two miles and threequarters. I he reservoirs for the Uroton aqueduct supply are as follows; I he Croton dam, already described, the Amawalk, lake Mahopac (completed in 1898)— area of watershed 19.05 square miles ; capacity. – 7.O77.935.000 gallons, elevation of flow-line, 405,660,583 respectively; Carmel, Barrett s pond, lake Glenida (completed in January, 1896) area of watershed, 20.26 square miles, capacity 10,070.000,000 gallons, elevation of flowline, 503>779o0.5. respectively; Boyd’s Corners (completed in April. J873)— area of watershed, 22.39 square miles, capacity, 2.727,437.000 gallons, elevation of flow-line, 593; Middle Branch (completed in October, 1878)-—are, 21.22 square miles capacity, 4.004,916,000; elevation of flow-line 372; Bogbrook (completed in Septembr, 1893)—area of watershed, 3.91 square miles, capacity. 4.145 -000,000. elevation of flpvy-line, 372; East Branch, or Sodom (completed in December. The Jerome Park reservoir, the western section of which will soon be opened, will have a capacity of nearly 300.000,000 gallons. It reinforces 1892)—area of watershed, 70.11 square miles capacity, 4,830,000,000, elevation of flow-line, 415,; Titicus, or Purdy’s (completed in July, 1895)area, 20.51 square miles, capacity, 7,167,000,000, elevation of flow-line, 325; lake Gilead, New Croton, area of watershed, 189.97, capacity, 32,000,000,000, elevation of flow-line, 196. In New ork city are the following: The High Bridge reservoir, 400 square feet, capacity, 11,000,000 gallons, depth of water, sixteen feet, elevation of t1ow-line, 209 feet, city datum, 212.61 Croton datum; completed 111 1898 at a cost of $100,000; Central Park reservoir (old), area, thirty-one acres, capacity 200,000,000 gallons, depth of water, twenty-nine feet, elevation of flow-line, 115 feet, city datum, 118.61. Croton datum, completed in 1842; Central Park (new) reservoir, area, ninety-six miles, capacity, 1,000,000,000 gallons, depth of water, thirty-six feet, completed in August 19, 1892. As has been told in this journal, a new source of supply, the Esopus, to meet a consumption of at least 5,000,000 gallons daily is being investigated and surveyed. Work will be begun on it at once. During 1900 the average consumption per day was as follows: Manhattan and The Bronx, 273,000,000 gallons ( it is now quite 300,000,000), Brooklyn, 93.000,000 ( it is now 100,000,000; Queens, 67,ooo, (it has considerably increased); Richmond’s statistics are uncertain as the supply is furnished from pri vate sources. 1 lie city intended to bring over water, via Bayonne, N. J.; but that has been de dared contrary to law. The supply for Brooklyn and Queens is from wells and surface water in Long Island; but a new source must be found for these two boroughs.
Chief Engineer J. Waldo Smith, of the Croton aqueduct commission, in a paper read before the recent West Baden convention of the American Water Works association, gave an interesting account of the methods used to increase the rate of construction on the new Croton dam. He pointed out that the condition of the water supply of New ^ ork city at the beginning of last year’s working season was such as to render imperative the completion of the dam to such a height as to allow the storing of a considerable quantity of water. About 290 feet of the southern end of the dam had been torn down to allow’ of masonry work superseding the earthen core-wall and gen eral strengthenong, besides. It was necessary to raise the masonry 180 feet above the foundation. I his southern extension of the main dam is about 290 feet long. As it had been built in an excavation deep in the hillside it was difficult to lay rapidly 80,000 to 100,000 yards of masonry. I o do so, after the dam bad been leveled up to a convenient height, two permanent riveted steel towers, weighing about forty tons each, were erected, on which were placed two stiff-legged, ten-ton derricks, with a thirty-foot mast and forty-foot boom, at the corners of the towers, the latter being built permanently into the heart of the dam and sealed tightly with concrete and mortar to protect the steel. I hey were twentylive by fifty feet by fifty feet in height, with steam supplied to one from the main 300-horsepower plant below the dam, and to the other from an auxiliary 200 horsepower plant on the top of the south hill. With this arrangement augmented bv many guyed derricks, nearly all placed outside the dam, and used for passing stone and concrete. 900 cubic yards were frequently laid daily and from 15,000 to 17.000 monthly. During the dayshift the mansonry was built up round the outside of the derrick towers, which are set with their upstream faces twelve and one-half feet back from the dam line. During the night-shift, the concrete was deposited in the lower level under the towers, where it could easily be swung m from the derricks and rolled or pushed down to position. T6 avoid the difficulty of handling large stones here, spawls only were bedded in the concrete. Care was taken to fill in close to the steelwork with fine concrete that would pack solid and seal it tightly. By the time the masonrv reached an elevation about fifteen feet above the tower deck, the derricks working in wells, which A ere later tilled up, timber trestle-work was erected partly on the back-fill and partly on the downstream face of the dam, on which derricks were placed, so as to keep the derricks off the wall as far as possible, in order to maintain a steady rate of progress. The top of the trestle was decked with a solid platform twenty-four feet wide and 300 feet long, made with three-inch plank laid on ten-inch and twelve-inch beams. This platform afforded room for the delivery and temporary storage of materials from the surface tracks, and on it were set six boom derricks for unloading and handling materials. With this system the masonry was built to Kl. 160, when a new platform was built. Four of the derricks were shifted to it for service in setting the masonry, while the other two remained on the first platform to pass up the materials to them. Three more platforms similar to this were built at intervals of fifteen feet, the ends of the extension being always commanded by stationary derricks seated on the old masonry. The upper fifteen feet of the masonry is only eighteen feet wide. and will be built by the two traveling derricks installed on the top of the main dam, wdiich will >vork from both ends to the middle of the extension, moving on the top of the finished structure. The steel towers could not be used above the height mentioned, as the section ot the dam had become too narrow, while, by placing the derricks on trestle-work, the entire working top of the dam could practically be covered. By the end of December the desired height was reached, leaving only a comparatively small amount ot masonry to be laid in January. The closing of the opening through the dam, through which the river ran during construction, was begun abort the end of December. It was interrupted by the flood of January 6, of this year, but was finally completed and the gates permanently closed on January 28. The melting of the March snows hastened the filling of the dam to about 125 feet deep, impounding some 14,000,000.000 gallons of water. The entire dam, except this southerly ex tension, had been built of rubble masonry laid in mortar, with facings of coursed ashlar.* The southerly extension was laid with rubble in concrete so-called Cyclopean masonry with the same facing of coursed ashlar, and the rapid progress is due quite as much to this change in methods of construction as to the steel towers ind trestle work. It is not claimed there is anything new in the method of building structural steel derrick towers into the dam. as just described; hut it is thought it might be interesting to know what progress has been made under rather trying conditions.
As Waterloo, la., has had more than one visitation of typhoid fever, it is argued (In some unknown process of logic) that such a thing could not have happened if the town had had a municipal waterworks plant!