Pipe Line Laid Cheaper After than Before War Period
Comparison of Costs of Parallel Water Conduits—Labor-Saving Devices and Improved Processes of Manufacture Secret of Economy
AN instructive comparison of costs and methods of construction is made by the author in the following paper. The rather remarkable correspondence in cost between the two conduits in spite of the tear time high prices prevailing at the time that the 37-inch installation was built is explained by him from the fact that in this instance machinery was used in the construction teork and an improved and therefore more economical type of material and construction employed in pipe and joints.
An interesting comparison is afforded of the combined cost of materials and construction in the case of conduits II and III of the Rochester. N. Y., water supply. These conduits, described in detail later in this paper, are two of three gravity conduits from Hemlock Lake, and the Canadice water is conducted into Hemlock Lake so that it reaches the city through the Hemlock conduits. They are laid side by side, generally ten feet center to center, conduit II being constructed in 1893-4 and conduit III twenty to twenty-five years later. In the following comparison the cost of right-of-way, engineering, etc., is excluded in both cases.
Conduit II is 138,238.57 feet long, cost $1,226,874.71. It is mainly 38 inch riveted steel pipe.
Conduit III is 134,605,07 feet long, cost $1,173,326.37. It consists of 7 miles of 37 inch cast iron pipe, and the remainder 37 in look-bar steel pipe.
The foregoing figures indicate that in 1893-4 the 38 inch conduit cost 23.4 cents per lineal foot per inch of diameter against 23.6 cents for the 37 inch conduit in 1914-1918. This close correspondence is mainly due to the methods employed in construction. In the early 90s materials and labor were cheap, and an army of workmen was employed, while during the late war, men were scarce, materials and labor high, and consequently the work was largely done by machine.
Two other items of the design which contributed to more economical construction of Conduit III were, first, the use of lock-bar, rather than riveted, steel pipe, which, due to a more efficient longitudinal joint, resulted in a 25 to 33 1/3 per cent, reduction in thickness where the pressure was high, and second, the construction of a 37 inch cast iron pipe, where under light pressure, at about the same cost as a 36 inch, by using a 36 inch Class D pattern with a 37 inch core, thus procuring a pipe 1.08 inches thick and weighing about 418 lbs. per foot.
Description of the Conduits
Conduit I. was laid in 1873-4, and consists of cast iron and wrought iron pipe, with lead joints. For 10 miles from the Lake it is 36 inches in diameter. For the next 10 miles to the storage reservoir at Rush it is 24 inches in diameter, and laid to a steeper hydraulic grade. Front Rush Reservoir to the distributing reservoir in Highland Park, a distance of about 9 miles, it is 24 inches in diameter. Its capacity to Rush is 6,125,000 gallons daily, and from Rush 6,750,000 gallons.
Conduit II was constructed in 1893-4 and follows the same general direction as Conduit I. After leaving the lake, however, it avoided the quicksand of the valley by tunnelling through the high ground to the east. This section is a masonry conduit 6 feet in diameter, 8,000 feet constructed in tunnel and 4.000 feet in open cut. It is built to a gradient of one in 4,000.
The intake pipe for Conduit I is about 1,000 feet long and 36 inches in diameter. The intake for Conduit II extends 1,500 feet into the Lake, and is 5 feet in diameter. From the lower end of the masonry section at Overflow No. 1 the pipe lines of Conduits II and III continue northerly toward the city. Conduit II from White Bridge to Rush consists of 38 inch riveted steel pipe from one-fourth to three-eighths inch in thickness, and about 17 1/2 miles in length.
Overflow No. 2 is about half way between Overflow No. 1 and Rush Reservoir, and at this point the conduit rises to hydraulic grade. The conduit between Overflows Nos. 1 and 2 crosses the Hemlock Outlet and Honeoye Creek ten times, and at these points is protected by concrete beneath the bottom of the stream.
Steel and Cast Iron Both Used in Pipe Lines
From Rush Reservoir to a gate vault in Clinton Avenue South near the city the pipe is riveted steel, 38 inches in diameter, except for a short distance near Rush and at the crossing of the Barge Canal where is is 36 inch cast iron. The total length is about 8 miles. From this gate vault, which is a junction point, Conduit II continues to Highland Reservoir, about seven-tenths of a mile, as a 38 inch riveted steel pipe, and a 36 inch cast iron pipe about1 1/2 miles long runs to Cobb’s Hill Reservoir. The capacity of Conduit II into Rush is 15,750,000 gallons and out of Rush 18,000,000 gallons daily. This difference is due to the fact that Rush Reservoir lies above the hydraulic grade line connecting the ends of Conduit II.
Returning to Overflow No. 1, at White Bridge, the northern end of the masonry conduit, Conduit III, constructed in 1914-18, commences as a 37 inch cast iron pipe and extends to Factory Hollow, a distance of about 7.7 miles. From this point it continues as a 37 inch lock-bar steel pipe through Overflow No. 2, following the route of Conduit II to Rush Reservoir and thence to the gate vault above mentioned in Clinton Avenue South, a total distance of about 18 miles. Its capacity into Rush is 18,125,000 gallons, and out of Rush 19,500.000 gallons, daily. This conduit, the same as Conduit II, crosses theBarge Canal as a 36 inch cast iron pipe, where both pipes are enclosed in an accessible masonry culvert with gate vaults and cross connections at each end.
The combined capacity of these three conduits is 40,000,000 gallons into, and 44,250,000 gallons daily out of, Rush Reservoir, and is sufficient to carry all the waters available from the Hemlock and Canadice watersheds, with such leeway as may be necessary in case any section is out of service for repairs.
Easement Agreements in Case of Conduit Lands
All of the conduits arc laid in easements obtained by the city. The agreements in the case of Conduit I only provided for construction and operation. Damages have to be paid to owners whenever excavations are made for repairs. The Conduit II agreements were broader and covered the right to “excavate, construct, operate and maintain a pipe or pipes. conduit or conduits, under, through and along said strip of land.” The easements were three and four rods wide. Conduit II was laid five feet east, and Conduit III five feet west, of the center line of the right of way. Where land was worth $30 per acre, we paid about $100 per acre for the easement. It is not fenced, but we maintain fences and gates at division lines crossing the right of way between adjoining owners. Where the conduit is laid in highway, an easement is obtained from the abutting owner for his half of the road. About $1 per rod was the minimum price, when there was no damage to trees.
Some Interesting Bits of History
The Rochester Water Works afford an interesting example of the evolution of an efficient water supply front small beginnings.
Seventy-one years ago the mayor of Rochester, in his inaugural, said: “It is hoped that our citizens will soon feel (he necessity of supplying our city with water by some means, both for their health and convenience.”
Six years later a communication was sent to the mayor by Elisha Johnson, which outlined a plan for supplying the city with water from the watershed of Little Black Creek. He estimated a consumption of 25 gallons per capita for a population of 60,000, and proposed a reservoir in the southwestern part of the city fed by an aqueduct of brick or stone four feet in diameter, two miles long, and with a fall of four inches per mile. In the following year. I860, $500 was appropriated for “the survey and plans for water works,” in accordance with which Daniel Marsh submitted a report embodying five distinct plans. In October of the same year a contract was entered into with the Rochester Water Company. Considerable work was done in building reservoirs and in laying conduit and distribution pipes, but after many vicissitudes the company collapsed early in 1872.
The following year the board of water commissioners was organized and work on the present system was begun. The original source of supply was Hemlock Lake, a beautiful clear sheet of water six and one-half miles long, one-half mile wide, and 86 feet deep. It lies between high hills 386 feet above and about 30 miles south of Rochester, and receives the rainfall from 48 square miles of watershed. The city also acquired, and has since exercised, the right to use the waters of Canadice Lake, its neighbor on the east. This lake is the same depth as Hemlock, about one-third the area, and lies 196 feet higher. Its watershed is 12.4 square miles, and its outlet stream has a watershed of 5.8 squares miles. The combined watersheds of the two lakes and Canadice Outlet, if completely utilized, will yield about 33,000,000 gallons per day. The annual precipitation in this region for the last 48 years has averaged 28.3 inches. Our experience indicates a net yield of about 500,000 gallons per square mile per day from the watershed. All of this supply is not available as extensive construction in dyking would be required.
Anticipated Needed Increase in Water Supply
Surveys are now under way in anticipation of the necessity of using the waters of Conesus Lake which lies west of Hemlock Lake, and of Honeoye Lake which lies east of Canadice. They are somewhat lower than Hemlock Lake but their waters can also be obtained by gravity. Conesus Lake has a watershed of 69.06 square miles, and Honeoye Lake a watershed of 39.3 square miles. The total combined watersheds amount to 174.56 square miles. At the above rate, and fully utilized, this would give us 87.000,000 gallons per day. If 75 per cent, of this amount is available during dry years we shall have available 65,000.000 gallons per day.
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Pipe Laid Cheaper After Than Before War
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Our present population is about 330,000. and it has doubled in the last 25 years. Our present use of water from this domestic system is about 86.4 gallons per capita, or a total of something over 26,000,000 gallons per day. These figures are complicated by the fact that a small portion of our population uses Lake Ontario water supplied by a private company. When all of the available watersheds above mentioned are reasonably utilized we shall have an ample domestic supply for more than double our present population.
Shores of Lakes Cleaned Up
About 30 years ago the city began the purchase of property around Hemlock Lake, and later around Canadice Lake. The shores of Hemlock Lake were lined with summer cottages, and up to that time a sanitary pail system of collection of night soil and garbage had been maintained by the city. The properties for 200 feet from the shore were purchased, and the cottages removed. In some cases whole farms were acquired. Plantations of conifers have since been made on the shores of both lakes, and constant inspection maintains the pristine purity of the supply.
Storage and Distributing Reservoirs
At Rush, nine miles from the city, a storage reservoir was constructed in fill and excavation on a clay hill at the time of the construction of Conduit I. The side slopes are lined with rip-rap and the basin has a capacity of 63,400,000 gallons at 16.5 feet depth.
Mt. Hope, or Highland, distributing reservoir at the south side of the city, was constructed at about the same time as Rush Reservoir. At a depth of 15 feet it holds 22,500,000 gallons. It is built on a sand hill, puddle lined, the lower half of the slopes rip-rapped to a 5-foot berm and the upper half above the berm, paved.
Another distributing reservoir was constructed in 1905-8 on Cobb’s Hill with water surface at the same elevation as Highland Reservoir, namely, 125 feet above the central portion of the city. Cobb’s Hill Reservoir has a capacity of 144,000,000 gallons at 25 feet depth, and is lined on the bottom with concrete and surrounded by a gravity seotion concrete wall backed up on the outside by a heavy earthen embankment. We therefore have in all the reservoirs an available storage, at the present rate of consumption, of about one week’s supply. The construction of this reservoir was described and illustrated by the speaker in a paper before this Society at its meeting here Sept. 11, 1910.
Mean Consumption Per Capita in City
Studies of the rate of consumption were made during the census weeks of the years 1900 and 1910. These rates plotted indicated that the use drops to a minimum of about 35 gallons per head, daily, and rises to a maximum of about 135 gallons. The mean consumption for the period of the test was 84.9 gallons per day. We have had single day’s use during very hot weather as high as 35,000,00 gallons.
The writer, although not a member of this organization, has been asked to prepare this paper by Mr. Little, with whom he has been associated in the city’s employ since 1891, when both started on the surveys and plans for Conduit II under the late Emil Kuichling, then chief engineer of water works.
In 1902 Mr. Little became superintendent of the water bureau while the writer remained in the engineering department where, under the last three city engineers, he has designed and supervised the construction of Cobb’s Hill Reservoir and Conduit III. and now has studies and surveys under way looking toward the utilization of Conesus Lake and Honeoye Lake. His early remembrance of looking into a walled excavation and being told it was a reservoir of the Rochester Water Company antedates the present water supply, and his first active entrance into the details of water works construction consisted in crawling through the 16 inch pipes when first laid in front of his home in 1875.
(Excerpts from paper read before the annual convention of the New England Water Works Association.)