ALLEGHENY’S WATER MAIN.
ALLEGHENY City, Pa., has a large water main now being laid from Troy Hill reservoir, to Montrose station on the Allegheny river. It will be, when finished, a little over 9 1-2 miles long. It is made of steel plates, half an inch thick; is 60 inches in diameter; will be 50,000 feet long; and 9,000 tons of steel will be used in its construction. It is sunk below the ordinary frost line, and during its whole length follows the undulations of the territory through which it passes. From the pumping station to the reservoir on Mount Troy the total elevation is 250 feet. To lay this pipe it was necessary to trench an average depth of 10 feet, the excavation being 8 feet at the top and 6 11-2 feet at the bottom. Altogether the excavation aggregates over 200,000 cubic yards of earth. At some places the trench Is from 22 to 25 feet deep, and in many places from 12 to 16 feet was the depth required through certain cuts. To assist in the excavation of this vast quantity of earth, a steam shovel was manufactured at Toledo, O., for this special work. It is the first of its kind ever made, and could dig from 1,000 to 1,200 cubic yards of dirt from the trench in 10 hours’ work; lifting a cubic yard and a half of dirt three times every minute, and accomplishing the work ordinarily done by 200 men. The contract for laying the main was undertaken by the firm of T. A. & R. G. Gillespie, of Pittsburg, Pa. The work was begun on June 27, and, it is expected will be finished by the middle of Decemberat latest. The water pipes were manufactured from steel plates from the mill of James O’Neil & Bros., Pittsburg. The plates, after having been planed and punched for the rivet holes are bent into circular form and riveted together in sections of four, each length being 24 feet long. Every rivet is driven and set under a 69-ton hydraulic pressure hammer, under which they are held until they are cold. Pneumatic agency caulks the pipes inside and out. Each section is then coated with Sabine coating material composed of Colorado asphalt, which renders them rustproof, after which they are baked in an oven for eight hours. In the trench the joints are riveted by pneumatic riveters, caulked round the rivets and seams, and then subjected to hydraulic pressure up to 25 pounds to the square inch—just double what they will have to bear when in use. There are 2,200 sections of tubing, each section weighing 9,000 pounds and requiring 392 rivets, of which 862,400 arc needed (weighing 600 tons in all) and requiring the punching of 1,724,800 holes. There are also nine 60-itich gate valves at different points along the line, weighing 52,500 pounds each, and five 60inch “ Y’s” from Mount Troy to the pumping station,each weighing 51,000 pounds apiece.
In connection with this main is the Venturi water meter which has been built for it at Providence, R. I., by the Builders’ Iron Foundry, of that city, the invention of Clemens Herschell, civil engineer, of New York. Ills operated by an electrical clockwork arrangement, and, when connected with the main office of the water depart* ment, will show at any moment the exact quantity of water passing through the main at a given time. It is about 40 feet long with a diameter of 60 inches at one end, tapering to 30 inches within about 10 feet of the other end, at which point is located the electrical apparatus that measures the water as it passes. The Venturi meter consists of a converging, followed by a gently dnerging tube; between the two is a short cylindrical piece, surrounded by a pressure-chamber which is connected with the interior by piezometer holes. A similar pressure surrounds the main pipe at the inlet end, and may also he applied to the main pipe at the outlet end, if it be desired to measure the loss of head in passing the meters. It is a fundamental principle Jn hydraulics, that the hydraulic pressure of the water against the interior of a pipe containing water in motion is equal to the hydrostatic head (to what the pressure would he if the water stood still), less the head due this contained velocity. As the indications necessary for the measurement of the water passing through a Venturi meter are merely the pressure in two little pipes, these same two pressure-pipes may be used to operatesev. eral mechanisms without interfering with each other, which would not he true, if, for instance, the pressurepipes contained a stream of water, instead of only static pressure. Thus a diagram can be drawn by them that will indicate the rate of flow through the meter for any convenient length of time. This makes the meter a socalled waste-water meter, used to find and locate leaky house fixtures iu cities. The Allegheny meter is the largest ever made as yet; but meters embracing the same principle are in use at Bellefield reservoir, Newark, N. .T., and elsewhere.
In laying the main some considerable engineering dif Acuities had to be overcome. Along the Butler plank road, for a distance of almost 7,000 feet one of the street railway tracks of the Bharpsburg & Etna line had to be removed and the work carried on so that trafiic on the public road and the other car track should not be interfered with. At Girty’s run a cut of 22 feet deep was required under the bed of the stream, the water being carried away through flumes. Under the creek the pipe was incased iu concrete 12 to 18 inches thick. In Millvale two dwelling houses had to be removed, and after the pipe was laid, replaced where they had been. In Sharpsburg and Etna much trouble was experienced in getting under the gas and water mains, and again in laying the water pipe under the bed of Pine creek. Along Dick’s run, on the hill, above Etna, the cutting was almost solid blue rock, requiring drilling ami blasting. On Troy Hill the digging was almost solid rock. The main passes under four railroad tracks, besides innumerable streams, water pipes, and gas lines. Between Aspinwall and Quyasuta, within a distance of 200 yards a perfect “H” is formed by the pipe. At night the work has been pushed under the gaslight furnished from mains laid to follow the pipe lines.