RESERVOIR REPAIRS AT ST. JOHN
IMPROVEMENT OF SOURCE OF SUPPLY.
Specially written for FIRE AND WATER ENGINEERING
St. John, N. B., had a satisfactory experience with its waterworks during the past year, chiefly with two of its reservoirs and intake B. The result has been quite an improvement in the East Side source of supply, although in the city itself little was done beyond laying a twelve-inch main in Mill street. That, with the enlargements referred to at Little River reservoir and at Silver halls, has made the works more efficient than ever before.
The principal work done during the year was that of increasing the capacity of Little River reservoir by raising the dam and spillway three feet and dyking the low land on the south side. As there was abundance of suitable clay and gravel on the spot, raising the dam and spillway was a easy work. Because of the lowness of the ground an embankment 700 feet in length had to he constructed. Its maximum height was nine feet; its average height along the southern shore of the reservoir, from the spillway eastward. 4.2 feet. The slope given the embankment was 3 horizontal to I vertical; its cubic contents amounted to 2,241 yards. The spillway was raised by bolting to the existing timber, three courses of birch, closely jointed, then laid up on the front, or water pressure side, with clay and gravel, forming an impervious dam, brick clay being laid against the timber. On the outer side stone boulderhave been closely laid to receive the impact of the falling water and help support the timber wall. The weir is 120 feet long with end walls three feet high running into the bank at each side a distance of about 20 feet, thereby forming a core to the embankment where it adjoins the wasteway and is thus bonded to it. About 970 cubic yards of earth, sixty cubic yards of stone, twenty and three-quarter tons of birch timber and 856 and one-quarter pounds of iron bolts were used. The bolts are of one inch diameter, and vary in length from thirty inches to four feet. This section of the work cost $538.45. The work upon the dam comprised the following: (a) Repairing the leak; (b) altering intake B; (c) paving the front slope; (d) raising the surface three feet and enlarging the dam. The Little River reservoir dam is an embankment 400 feet in length, which was built by the Saint John Water company in the years 1850 and 1851. according to plans and specifications of George H. Bailey, civil engineer, of Boston. A clay core formed the heart of the embankment, and it was flanked with gravel on either side, the upstream side sloping about 2 to 1, and the downstream, about 1 1/2 to 1. Its overflow was at a level of fifteen above the bed of the stream, an additional height of four feet having been obtained later on. The spillway was at the southern end, so as to save expense of purchasing land for its construction. The increased height was effected previous to 1854, as at that date that end was referred to as the old spillway. On the night of November 13, 1854, after a heavy rain, the surplus water carried away the dam at that point to its foundation for a distance of about 150 feet. The breach was repaired by driving a close row of spruce piles across the gap and into the natural bank for about 200 feet. Against the upstream of these piles deals were spiked, and a fill of mixed material comprising gravel, clay, and cobblestones was thrown in to restore the embankment. Yet, with all this, the dam leaked at the rate of about 800.000 gallons in each twenty-four hours. To repair this leak, wherever there was clay core it was stripped off, and its top raised to a level of eighteen inches above that of the intended level of the reservoir overflow, or to El 164.50. The top of the clay was at a level of 157.00 or three feet below that of the existing overflow level. The material above it was only coarse gravel, which was removed, and its place filled with clay and gravel well puddled together in proportions of about 1 gravel to 2 clay. This was continued for about 230 feet, in which the puddle was raised seven and one-half feet, the clay core ending abruptly there, and in its extension the piling mentioned above beginning. The row of piles did not extend southwards in continuation of the direction of the clay core, but deflected considerably to the right, or westwards. In bonding the new work a lap of six feet was made on the western side of the core, which, being the outer side from the water, was performed without difficulty. The new puddle trench was then proceeded with southwestwardly using the piling and planking, already described, as the upstream, or reservoir-ward wall, and driving spruce plank sheeting to sustain the outer slope of the dam on the opposite side of the trench. At the beginning of the work a steam syphon was sufficient to remove all the water that came, even at a depth of eighteen feet: but. after advancing twenty-five feet into the breach a depth of eighteen feet, a Smith-Vaile steam pump was used. It had a six-inch steam cylinder. four and one-half-inch plunger, and six-inch stroke. Tt was satisfactory. It served its purpose until seventy feet into the old breach was reached, by which time the waters fenced off in that direction had become so concentrated that a larger pump had to be imported from the Smith-Vaile works in Dayton. Ohio, causing a second suspension of work. The dimensions of this pump are: Steam cylinder, seven inches diameter; water-piunger, four and one-half inches diameter by ten-inch stroke. The capacity is more than double that of the other, or as 2.11 to 1. A thirty-five horsepower boiler had also to he obtained. The work got on better; but even these pumps were found insufficient as the trench deepened, wherefore, an old city steam fire engine, with two double-acting pumps, with four-inch plungers and twelve-inch stroke, was called into service, and did excellent work. The pumps had not to work continuously. The trench was dug in sections, each pit being from eight to sixteen feet long, except the last, which was thirty-six feet. As the pit deepened, the water increased, and a pump was put on as required till the bottom was reached, when all three pumps were taxed to their utmost capacity. As the puddling progressed the pumping dropped off. The total amount of clay used was 800 cubic yards, and there are still 400 to he done, when it is hoped the leak will be stopped, unless the water flows through the soil beneath, for the core was never placed on ledge, neither was a positively impervious foundation obtained when the dam was built. The total cost of the work (including hire of boiler, purchase of two engines, etc.) was $3,413.90—at the rate of $4.-27 per cubic yard. Intake B (the original intake was A), is the head work or terminal in the reservoir of a twenty-four-inch pipe laid in 1881 in the place of the old Paper mill penstock, connected to No. 2 main 310 feet from intake B, which at first had a timber roof. A brick arch of eight-foot span has taken the place of that roof. The wooden slides have been extended four feet to the. raised water surface in cast iron, with a panel inside containing a measuring weir. The weir being no longer available, owing to the raising of the water, has been taken out. and a large, fine-meshed screen placed instead. Its height is eight feet eleven inches; breadth, two feet eight inches; brass wire. No. 22 gauge, mesh sixty-four per square inch. There are four outside screens, of six feet two inches high by eleven and one-half inches internal measurement; gauge of wire No. 12; meshes nine per square inch. All are secured in gun metal frames; grooves double to allow of the spare screen being lowered before raising the other. The intake is entered by a cast iron manhole, flush with the surface of the dam, where is also a plate covering the inner screen. The outer screens are managed from a wooden staff, extending from the dam to a point immediately over the cast iron slides for these screens. The low level of the water six feet below the spillway afforded the opportunity to pave the face of the dam by imbedding boulders weighing from fifteen pounds to three hundred pounds. The larger stones were laid in the bottom course (about El 154.00) the bed in the direction of the greatest axis of each stone being as nearly as possible at right angles to the slope of the dam. About 300 yards of this pitching was done, when a sudden rise of the water put an end to the work. The top of the dam is now raised three feet over a length of 400 feet, top width eight feet; slopes for the present about 1 1/2 to I. The building of this gravel mound above the embankment and its approaches affords perfect protection, and its function is only precautionary, as its base, which is the old top of the dam. is from 12 to 18 inches above the level of the new spillway, making the top of the embankment, therefore, fully four feet above the level of the spillway as raised.
DETAILS INTAKE B. LITLLE RIVER RESERVOIR, ST. JOHN, N. B.
The stone dam at the Silver Falls pumping station was also raised three feet for power purposes. The enlargement, which was on the downstream Ade, was made by building an uncoursed rubble wall about one foot thick, laid in Portland cement 1 :.3, and backed with concrete two feet thick at the base and one foot at the water line—proportioned one of cement to four of gravel. The hearting of what was above the waterway was 1:5 packed with granite chippings; the facings were of granite. The only through stones are in the coping of the spillway. The level was raised two feet, the intention being to obtain the other foot by placing a dashboard to be lowered during freshets and raised during droughts. The increased height backed still water t.ooo, instead of only 400 feet above the dam: the additional foot will back the water about 1,700 feet. The dimensions of the dam below the sill of the spillway are: Base nine feet six inches; top, four feet; height, seven to ten feet. The upstream face is vertical; spillway thirty feet long; parapet round embankment, four feet wide by four feet high. The whole structure is bonded to the slate rock cleft, through which the water of the falls originally poured.
Bv raising the dam and spillway weir of the Little River reservoir three feet the surface of the reservoir has been increased from forty-six and one-half to fifty-five and one-third acres. Its former capacity of 80.000,000 gallons is now 122,000,000 gallons—an increase of fifty-two and one-half per cent—increase enough to supply the district for nine days. The total overflowage at the spillway during tQOwas 480,000,000—enough to supply 96.000 inhabitants at St. John’s liberal rate of 121.88 gallons per capita. If this number is added to the population supplied the amount of water flowing into the Little River reservoir in 1902 could have supplied a city of 132,000 people. All that is needed, if the population increases threefold, whenever want arises, is to build another reservoir in Little River valley ; and the more reservoirs settling basins, the better and cleaner the water. The engineer and superintendent of the waterworks is William Murdock, who understands and fittingly carries out his work.