REPAIRING A THIRTY-INCH SUBMARINE WATER MAIN.*
THE thirty-inch main which forms the subject of this paper is one of three force mains which connect the principal pumping station of the Hackensack Water company, reorganized, with its reservoirs at Weehawken, N. J —the distance between the two points being practically fourteen miles. The main in question is not laid the entire distance between the pumping station and reservoirs, but is connected to a twenty-inch and twenty-four-inch main at a place known as Ridgefield, N. J., which is ten miles south from the pumping station. The thirtyinch main was laid during the season of 1897 and 1898, and after being carefully tested between each gate as the work progressed, was put into use in April, 1898, and continued in service without any interruption until the afternoon of Friday, August 19, 1898, when the pressure at the pumping station of 102 pounds, against which the engines were working, suddenly dropped so low that it was evident that a serious break had taken place somewhere on one of the force-mains. The three force-mains referred to, extend over a distance of practically forty miles, and at several intersections are connected with each other. At the time the break occurred,the engines were running with these connections all open, in order to reduce the working pressure as much as possible, and, consequently, the cost of operations. As the distance to be covered was so great, considerable time was consumed by the men in getting to the gates which had to be closed; but, as soon as the connections were closed, which enabled us to prove each main separately, the difficulty was found to he with the thirty-inch main, and the break was finally located at a river crossing, on the bed of which the main lies, and over which there was eleven feet of water at low tide.
With the thirty-inch main out of commission and crippled in a place where it required no argument to persuade me to believe that to make the repair meant a question of weeks rather than days, and with our daily consumption over 1,000,000 gallons greater than what could be delivered ihrough the twentyinch and twenty-four-inch mains, even after raising the pressure to 120 pounds, and with a stock on hand of 20,000,000 gallons, I began to see numerous visions of outraged citizens rushing into my office and demanding by what authority T had shut off their water supply, without first giving them proper notice. It wae decidedly too evident for comfort that either more water muet be delivered into the reservoire at Weehawken than it was then possible to do—running at the pressure named on the twentyinch and twenty-four-inch main, or else, to prepare for a water famine as gracefully as possible.
About 2,500 feet north from where the break occurred, the street on which the thirty-inch main is laid intersects a turnpike, along which the twentyinch main lies, and from this point south the mains parallel each other for practically a mile. Three hundred feet north from this point of intersection there is a gate on the thirty-inch main, which is the first gate north of the break, and was, consequently, closed. I felt positive that if the twenty-inch main were connected to a point on the thirty-inch above the closed gate, and delivered through the thirtyinch from the pumping station into the twenty-inch at this point, my advantage would be the loss of friction between these two points, and would result in an increased delivery of from 2.500,000 to 3,000,000 gallons per day. Ae we were fortunate enough to have sufficient material on hand to make this connection, which required 300 feet of twenty-inch pipe, a thirty-inch by thirty-inch by twenty-inch branch, a twenty-inch by twenty-inch by twenty-inch branch, a twenty-inch gate, bends, etc., work was begun early on Saturday morning, and by working continuously with alternate gangs, was completed late on Sunday night. After this connection was opened, we were able to deliver 12,500,000 gallons a day at 120 pounds pressure, which showed the effective value of the by-pass to be 3,150,000 gallons a day. which enabled us to breathe so far as a fear of water famine was concerned. The value of the by-pass was also emphasized a week later when, due to the exceedingly warm and dry weather, our daily consumption exceeded 13,000,000 gallons.
*Paper rend at the twentieth annual convention of the American Water Works association, at Richmond, Va., May, 1900.
The method adopted in making the repair to the thirty-inch main is not based upon any established precedent, so far as I know, but upon what seemed to lie the best, quickest, and cheapest way to accomplish the result. It seemed practicable to make the repair in two ways—either by sinking a caisson in the usual manner, or by raising the pipe up off of the bed of the river and high enough above low tide to permit the removal of the broken length, and the substitution of a new one. After viewing the case from all sides, it seemed to ns that the latter method was practicable—and that it could be done more quickly and for less money than the former. We decided to make the attempt. After engaging a piledriver, scow, tackle, diver and bis apparatus and making provisions for such other requirements as were needed, the work was begun. On the first examination the diver reported that he had found the broken pipe, which is known as the “Ward joint type.” cracked on the bell end, parallel with the axis of the pipe and very near the top, that the slit followed along the pipe for about three feet, then turned at an angle of about ninety degrees, and passed round the pipe for a distance of about three feet. The diver further reported that the opening was one and one-half inch to two inches wide.
The river across which the pipe lies is practically 500 feet wide; but the location of the broken pipe wits about 100 feet from the north shore at low tide, and exactly in front of a draw in a bridge which crosses the river at this point In general the method of operation decided upon was to drive pilesin bents, in the centre of each length of pipe, from the shore out to the break, cap the piles with twelve-inch by twelve-inch yellow pine, break out a length on shore above tide, and raise the pipe up gradually and intact about three feet above low water, and hold it suspended while the broken length was removed and a new one substituted. In order to facilitate the work, it was first necessary that the pipe be free to move endwise on the shore end; otherwise, in raising the pipe from its bed, we should be lifting against an inverted arch. Some difficulty was experienced in breaking the shore pipe, which is one and one half inches thick, and weighs 550 pounds per foot, but it was finally accomplished, after several unsuccessful attempts, with the use of dynamite.
As soon as the piles were driven and capped, the diver passed a heavy chain round the centre of each length, to which was hooked a three sheave block and fall, which was bung from nil eye-bolt in the cap piece on top of the piles. When everything was in readiness, the process of lifting was begun, which required a considerable time, as only a short lift could be taken at any one time, and every change from one tackle to another involved the moving of the piledriver from which power was taken. Measurements were taken almost continuously from the surface of the water, which served as a good level, in order to guide the work, and to be sure that the joints were not being unequally strained. Some difficulty was experienced in starting the pipe from the bed of the river; but, after it was started, the lifting continued until the pipe was several feet above the bed of tlie river, and the weight, which represen’ed 60,000 pounds, was supported by the piles and capping. By rigging another block and fall from the shore end of the pipe,which was now susperded.to the main land, very little difficulty was met with in separating the the two lengths, as the crack in the bell was about two inches wide, and,therefore.did not offer much resistance. After this was done the broken pipe was raised up until it was about three feet above low tide, which enabled us to cut off tlie broken pipe, and remove the spigot from the adjoining bell. With this part of the work done, it now remained to raise the end still lying on the bed of the river to the same level as the first section, which was accomplished by driving fourteen more piles in seven bents—capping the same as in the previous case, and by repeating the operation of lifting.
After the pipe was raised to the proper level, a new length was put in place, the joints run, and the work was ready for the final lowering. As the pipe when ready to lower formed an arch, the radius of which was about 100 feet, and in its descent the arch must necessarily be reversed, it was absolutely necessary to keep the pipe, from the break inshore, suspended, so that it should be free to travel endwise, until the balance of the picked-up section was down on the bed of the river, after -which the inshore end was lowered into place. Before making the final connection on shore, the end of the pipe was plugged, and the section in the river xvas tested for leakage. After the pressure had remained full on for an hour or more, it was turned off, and the falling off of the pressure as shown by the guage was a satisfactory evidence that there was some leakage at the joints, due to their movements in raising and lowering. These leaks, which were several in number, and all small, were found and made tight by the diver. After the testing was completed the final connection was made, and the main again put into commission on Thursday, April 8, 1898—the repairs having been made in fifteen days, at an actual cost of $2,258.43. The cost of material and labor for making the bypass connection was $1,300.34, so that the total cost by which we shall probably “remember the main” amounted to $3,558.77.
When the break in the river took place, it was accompanied by an effect which in my experience was unusual. The distance between the pumping station and the break, as I have stated before, is practically ten miles south, and yet, about one mile north from the pumping station a twelve-inch main was broken, and one and one-half miles south twosix-inch mains were broken, simultaneously. When this information reached me, I felt very much as the child did who shouted to its mother from the bathroom to “bring her another sponge,” and, upon the parent asking what the matter was with the one she had, replied that it was “all full of holes and leaked awful.” The water pressure at the engines at the time of the break was 102 pounds,and whether the failure of the smaller pipes was due to the exceedirgly sudden relief on that end of the system or from some other cause, I am unable to determine, but the fact remains, and personally will be regarded ae one of the mysteries of hydraulics.