Submerged Pipe to Fort Greble.
To avoid for the future having to carry water in boats to the garrison of Fort Greble, on Dutch Island, Narragansett bay, a regular pressure supply from spring water stored in a 400,000-gal. reinforced concrete reservoir at Saunderstown, R. I., is brought by means of a submerged 6-in. cast iron pipe some 4,150 ft. long. This line of pipe is laid where the water has an average depth of 35 ft., a maximum of 60 at low water, a strong undertow, a tidal current of 4 miles and a rise and fall of nearly 5 ft. To lay this pipe so that it should not he in the wav of heavy anchors a trench was dredged. The bottom turned out to he, not mud. but firm clay mixed with shells. The sides of the trench were cut almost vertical; the width varied from 8 to 15 ft.; the depth was almost parallel with the surface. One great difficulty was found in the fact that the alignment of the pipe was diagonal to the current, which rendered it hard to keep the dredge at work. Much time was lost thereby; but each of the two dredges accomplished 100 ft. of excavation daily, and although the dredges had to return to harbor nightly, and sometimes only one tide could be utilised, the work was occomplished in about forty-five days with thirteen men. To carry the pipe and afford a working platform for connecting it a 130-ft., 3-masted schooner was employed and properly secured at right angles to the pipe, except when forward movement was called for, when the control was by no means satifactory. On an average each 12-ft. section of pipe weighed about 1,000 lb. The connection was made by fours, Ward joints being employed with 28 lb. of lead in each joint caulked by hand. The section was then lifted and placed in a wooden chute about 100 ft. long, the inclination being about 45° with the horizontal and one-half submerged. A wire rope was passed through the first section of the pipe and carried on shore through a snatch-block and back to the dredge engine. This rope hauled the end of the pipe: more pipes were added as it went forward; and finally the extremity was brought to high-water line. As the schooner was advanced. 4-pipe sections were successively and successfully added until the strong current caused the abandonment of the jointed chute at a point 700 ft. from the shore, it being found that, with the advancement of the schooner 48 feet so as to effect another pipe-connection, it could not be kept in line. The pipe was then transferred to a lighter, the flexible lower sections of the chute were removed, and the pipe hung hy its own joints from the lower end by the rigid chute to its hearing in the trench. The chute hung from a fixed boom from the lighter, which was kept anchored on the pipe line for a length of 2.000 ft. At that distance it was found it would cause less strain to the line to lower it into the trench whenever pipe-laying ceased for the time being, the schooner then returning to harbor, while the dredge stayed anchored at the end of the pipe, which was buoyed before being released and recovered on the resumption of operations. During the operations the work was done most easily in the deeper water, 84 ft. being on one occasion unsupported uninjured between the end of the chute and the hearing in the trench—a portion that afterwards required less caulking than the rest. Most of the laying of the pipe took place during the storms of February and March, when sometimes nothing could be done for days together. while, on the contrary, as much as 1.000 ft. would be laid in nine hours. The last length of 48 ft. hung from the lighter, after she had been brought close to shore at high water at a point iust above the low-water mark. The land portion had already been laid, and, when the two were connected, by pumping in air at one end and driving out the water little by little throughout the length of the pipe to the other end a lest was made of supplying the water. A diver followed abreast of the water, as it went back and noted where the escaping air showed leaks. Those lie caulked with a Boyer pneumatic hammer operated under a 90-ft. pressure. Even the deepest part, this was sufficient to exhaust against the pressure-head without any need of another exhaust-pipe reaching above the surface. Nr, leaks of any importance were discovered, nor had the pipe suffered any injury. Whatever leaks were found on the under side of the pipe, an hydraulic jet. operated by the diver, washed out the soft material in the bottom of the trench, and the caulking of the joints was easily accomplished. On the completion of the tost the trench was hack-filled, the material being dug deep alongside and thrown over the pipe hy a dredging bucket. The leakage to be allowed for was 1 cu. ft. of water per 100 lin. ft. of pipe per hour under a pressure of 150 lb. Tins amount was much less than was actually found. The leaks were the unavoidable results of the back and forward movements, which could nn hm compress the lead in the joints and made vacancies which could not he filled, when the pipe was again displaced. What made these joints such a success was turning the pipe at each bell and shrinking on it a welded 2.3-in. band for every joint. The pipes had their ends so carefully machined that no yarn at all was used in any joint.