FEATURES OF THE SOMERVILLE WATER SYSTEM
The water supply to the distribution system, owned by the city of Somerville, Mass., and commenced in 1868, is furnished from the works of the Metropolitan Water and Sewerage Board. The city works are under the control of a Water Commissioner, performing the duties of registrar and superintendent. Commissioner Frank E. Merrill entered the department in 1890, became superintendent in 1897 and was first appointed commissioner in 1901. E. W. Bailey, city engineer, has charge of the engineering work of the department. There are forty regular employees. The Metropolitan system, taking water mainly from the Nashua river at Clinton, furnishes supply in two systems. A report on conditions in Somerville, issued by the Committee on Fire Prevention of the National Board of Fire Underwriters, gives the following information relative to the Somerville water system: The low service is supplied from two 48-inch mains of the Metropolitan system extending from the Chestnut Hill pumping station to Spot Pond. One of these mains connects with the Somerville system through a 16-inch Venturi meter at Broadway and Willow avenue, and an emergency connection, normally closed, through a 16-inch Venturi meter, at Willow avenue and Elm street. This main also has closed unmetered connections to 30-inch and 24-inch supply mains which extend from Mystic reservoir, elevation 157, to Charlestown. The other supply main is connected to the Somerville system, through a 24-inch Venturi meter at Webster avenue and Tremont street and a 16-inch metered connection at Pearl and Walnut streets; this main has a closed connection through a 30-inch Venturi meter to the Charlestown 30-inch supply main at Pearl and Walnut streets and a closed unmetered connection at Broadway and Fellsway West to the Charlestown 24-inch main. The Charlestown supply mains have emergency connections to the Somerville system, normally closed, through Venturi meters at four points and an unmetered connection at one point. The high service is supplied through a 10 inch branch of the main from Fells Reservoir, capacity 41,400,000 gallons, at elevation 271; this reservoir is supplied through a single 36inch line from the Spot Pond pumping station, the equipment of which consists of two pumps, a 10,000,000-gallon and a 20,000,000gallon, and three boilers. The 16-inch line has connections to the Somerville sv-tem through a 12-inch Venturi meter and check valve at Boston avenue and Dearborn Road, and a 16-inch Venturi meter at Broadway and Cedar street. Supply mains are well provided with gate valves and blow-offs.
Consumption, which is based on Venturi meter measurements, is highest during periods of extreme cold when fixtures are left running to prevent freezing or in summer when large quantities are used for sprinkling. The maximum day’s consumption in the summer of 1914 was 7,210.000 gallons on June 24, and in winter was 8,670,000 gallons on February 17; the maximum hourly flow for these days was 12,150,000 gallons and 10,950,000 gallons, respectively. In 1915, the maximum days were 6,770,000 gallons on September 16 and 7,730,000 gallons on February 3, with a maximum hourly rate of 9,450.000 gallons and 9,900,000 gallons, respectively. It is estimated that the night rate of consumption is about 50 per cent, of average daily rate. Up to May, 1916, the average daily consumption was 6,131,900 gallons, the estimated population being 88,720 and the gallons per capital, 69. The number of services was 13,300 and the number of meters was 9,255, The figures for the high service were Average daily consumption, 1,428,200 gallons: estimated population, 25,373. Low service figures were: Average daily consumption, 4,703,700 gallons; estimated population, 63,347. It was reported that no fire services are metered. Under the provision of the Metropolitan Water Act, the city is required to install at least 411 meters each year on services previously unmetered until all are metered, and to meter all new services.
The low service supplies about two-thirds of the city, including the manufacturing and packing house district and most of the mercantile sections. A short 20-inch and two 12-inch mains extend from the Metropolitan connection at Willow avenue and Broadway, a 20inch and a 16-inch from the connection at Webster avenue and Tremont street, and a 16inch and two 12-inch lines from the connection at Pearl and Walnut streets. These mains interconnect through a system of 10-inch and 12inch secondary feeders. Minor distributers are mainly 61inch with a moderate amount of 8inch and small amount of 4-inch, in general well gridironed. The high service supplies principally residential sections in the western, central and a small area in the north central section of the city. A 14-inch main extends east from a connection with the Metropolitan main at Broadway and Cedar street, supplying 10 and 12-inch secondary feeders in the larger area of the High service, mainly well spaced, with a 12-inch extending into the western section of the service, which is also supplied through a 12-inch main extending westerly a short distance from the Metropolitan connection at Boston avenue and Dearborn Road and reducing to an 8-inch. There is an emergency connection to the Arlington distribution system, a connection with check valve to one of the Metropolitan mains from Mystic reservoir and several check valves between the High and Low service mains. Minor distributers are mainly 8-inch with a moderate amount of 6-inch. A 12-inch main extends from the southeastern part of the service into the packing house district for fire purposes.
Charts from recording gauges of the Metropolitan Board located at the repair shop, on the High service, and at the Public Library, elevation on the Low service show average pressures to be: High service, day 85, night 90; Low service, day 30, night 32; pressures on both services are steadily maintained. In May, 1916, pressure readings were taken between 9 a. m. and 1:30 p. in., under normal conditions of operation, at 44 hydrants distributed throughout the city, with results as follows: Whole city—average, 57; maximum, 88; minimum. 36. Low service—average,. 53; maximum. 65; minimum, 36. High service— average, 65; maximum, 88; minimum, 46.
AU pipe is cast iron. Some of the original pipes laid in 1868 are still in use. The distribution system pipes are 95.28 miles in length, an increase of 10.24 miles since August, 1906. Pipe ranges in diameter from 4 to 20 inches Mains are stated to be flushed through hydrants or blow-offs, of which there are 173, when sediment is complained of. Some of the mains, crossing where the railroad tracks are depressed, are laid on the bridge and exposed; no trouble has been experienced from freezing. Mains are laid with to 5 feet of cover; average frost penetration 3 ½ to 4 feet. Pipe is purchased under specifications of the New England Water Works Association, Class D, and is inspected at the trench before laying. All pipe is laid by the department.
The total number of gate valves in use January 1, 1916, was 1,682. All open to the right; those 14 inches and larger are geared. Valves set in the squares and all those geared are in wooden or brick vaults; others have the customary iron gate boxes. Valves are generally located on property lines at street intersections. In a representative residential district. the average length of main that would be cut out in case of a break is 720 feet, with a maximum of 2,100 feet, with 17 out of a total of 81 lengths over 1,000 feet. On the mains 12 inches and larger in size the average gate spacing is 820 feet, with a maximum of 2,400 feet. Valves are operated as occasion requires.
All hydrants are of the post type and open to the right. The total number in use January 1, 1916, was 1,153 public and 61 private. Nine different makes are in use, about 25 per cent, being Holyoke. Ten per cent, have two 2 1/2inch outlets, a few, three or four 2 ½-inch outlets, and the remainder one 4 1/2-inch and two 2 1/2-inch outlets. About 10 per cent, have 4inch branches to mains and about 30, on the larger sized mains, have gate valve on branch. Hydrants are located within the curb at street intersections and on long blocks at intermediate points. Locations are determined by the commissioner. All hydrants have automatic drip valve; a few are connected to the sewer and others drain into pockets of loose stone. No hydrants have been found frozen at fires in recent years. Hydrants are only inspected in winter. The average area served by each hydrant in the closely built-up portion of the city is 88,600 square feet. Hydrants used by other than the fire department are operated by men detailed from the water department. There are 79 water posts, distributed throughout the city, used for filling sprinkler wagons.
The recommendation relative to water supply contained in the report include: Supply Works—That, pending the installation of additional pumps at the Spot Pond pumping station and additional mains of adequate capacity from Fells reservoir .to the Somerville High service, two pumps of 5,000,000 gallons capacity each, electrically, gas or oil driven, be installed in the old pumping station, corner of Broadway and Cedar street, with suction connections from the 30-inch Metropolitan main and a 16-inch discharge on Cedar street to the High service main at Highland avenue; provision to be made to start one pump on receipt of all alarms of fire within the High service areas. That the connection between the 48inch Metropolitan main and 12-inch city main at Elm street and Willow avenue be kept open at all times. Mains—That the distribution system be strengthened by the early installation of mains. A. In mercantile and manufacturing districts, 5,000 or 6,000 gallons a minute. B. In closely built residential districts, 4,000 gallons a minute. C. In outlying residential districts. a minimum of 1,500 gallons a minute. That the following be adopted as the standard minimum sizes of mains used for hydrant supply for all future construction: A. In residential districts, 8-inch; 6-inch to be used only where they complete a good gridiron, and in no case in blocks 600 feet or more in length. B. In mercantile and manufacturing districts. 8and 12-inch; the former to be used only in sections where they complete a good gridiron, and the latter for long lines not cross-connected. That the distribution system be equipped with a sufficient number of gate valves, so located that no single case of accident, breakage or repair to the pipe system in important districts will necessitate the shutting from service a length of pipe greater than the side of a single block or a maximum of 500 feet, or in other districts lengths greater than two sides of a single block, with a maximum of 800 feet. That in new installations and all hydrants replaced, connections to hydrants be equipped with gate valves. That an inspection of hydrants be made in the spring and fall of each year, after use at fires during freezing weather and daily in high value districts during protracted periods of severe cold. That the threads of hydrant hose outlets conform to the National Standard.