The Washington Water System

The Washington Water System


When the water system of Washington was first planned it was decided to take the supply from the Potomac river, Rock creek and the Eastern branch, as well as from numerous springs in and about the city. On January 25, 1851, the Secretary of War submitted to Congress a report from a corps of topographical engineers. It was proposed to build a dam to obtain from Rock Creek a supply of 8,000,000 gallons per day, which was considered sufficient for the city for forty years to come. At that time the population of Washington was a little more than 40.000, and it was proposed to supply 1,500.000 gallons daily, or a per capita supply of 37 gallons. Col. G. W Hughes, who headed the engineering corps, said: “This is the highest calculation I have seen, and is no doubt ample for users and for the city, except for manufacturing purposes.” This was the first step taken towards establishing a water system for the District of Columbia. From time to time until the pres nt, improvements have been made, and to-day the system is fully up to date and is of sufficient magnitude to supply the 350,000 population of the capital city. Now all water supplied to the District of Columbia is taken from the Potomac river at Great Falls. 14 miles above the city. A masonry conduit conveys a supply from a diverting dam at Great Falls to storage distributing reservoirs within the District. Owing to the range of elevations of about 400 feet, distribution is accomplished in five separate services. The low service is supplied by direct gravity flow from the distributing reservoirs, the higher service by pumpage from lowservice reservoirs and mains, two of the latter services having equalizing and distributing reservoirs of great capacity. The drainage area of the Potomac river above Great Falls is 11,000 square miles, with a minimum stream flow ot about 700,000,000 gallons per day. The diverting dam which spans the river above Great Falls and the Potomac is a masonry structure of rectangular section, 7 feet 9 inches to 8 feet 3 inches wide with rip-rap backing on the up-stream side; it is 2,877 feet high and average height eight to 10 feet, with extreme of 20 feet. The length of spillway is about 2,000 feet at elevation of 150.5. The water passes at the dam through the feeder and gate house to the conduit which leads to the city. This feeder is of masonry, 256 feet long, 9.5 feet in diameter, with invert at elevation 139.5. The water level is permanently maintained at the upper gate house at an elevation of 151. The normal elevation of water level at Georgetown reservoir at the lower end of the conduit is 146. When the water stands at this level the capacity of the conduit is about 65,000,000 gallons daily. With the level of Georgetown reservoir drawn down to elevation of 144, the capacity of the conduit is about 76,000,000 gallons, and with the wat.r level at 140.7 the capacity increases to about 95,000,000 gallons. To afford a distributing center within the city limits, a reservoir and tunnel to supply from Georgetown reservoir was begun in 1884, but was never completed until 1901, owing to a cessation of work ior several years. The pumping plant consists of four engines at U street station wdth a combined capacity of 16,000,000 gallons per day; two engines at T r u m bull street station of 20,000,000 gallons c a p a c ity each, also an 8,000,000-gallon Barr engine to supply the second high-level service; 5,000,000gallon Nordberg pump to supply second or third high service, and a new Holly pump of 2,500,000 gallons capacity in reserve. The total pumping capacity in this station is 50,500,000 gallons. Reno pumping station has two small triplex gas-engine pumps of 540,000,000 gallons combined capacity per day, and the filter station pumping plant has centrifugal pumps with an aggregate capacity of 40,000,000 gallons; two pumps of 2,500,000 gallons capacity each furnish water for washing filters and for fire protection. The average daily consumption is 70,000,000 gallons; the average normal pressure in the business center of the district is 40 pounds. There are five services services in the system as follows: The low service supplies the greater part of the city, including the congested value and minor mercantile districts, as well as practically all of the manufacturing establishments. Thr high-pressure firemain system for the protection of this district has been designed by the water department. The first high-service system is supplied by direct pumpage from Trumbull street station and furnishes a thickly settled residence section on Capitol Hill in the easterly part of the city with an estimated population of 50,000. The second high-service system is supplied from the Brightwood eservoir at an elevation of 276 feet and furnishes a large section in the northern part of the city with a population of 75,000. The third high service is supplied from Reno reservoir, and the fourth high service supplies a section in the western part of the District from the Reno standpipe. There are 440 miles of pipe in the distribution from 3 inches to 48 inches in diameter; about 5,000 gate valves of the Eddy pattern and 25,000 hydrants of various makes and 200 of the high-pressure type.


The new sand-filtration plant is situated on an elevation north of the city, about two miles from the Capitol, and covers a space of 40. acres, comprising 29 filter beds, pumping stations, gatehouses, storehouses and a chemical laboratory, where daily analyses of the water are taken. Two years and a half were required to construct this plant. At present about 70,000,000 gallons of water have been treated daily. The first reservoir is nine miles below Great Falls and is formed by damming a natural valley. The second reservoir is 12 miles from Great Falls and is built with embankments on hillsides. Very recently a tunnel has been constructed from the second reservoir to a center point in the city near Howard University, and a third reservoir has been built at the end of the line, and is known as the Washington City reservoir. The total capacity of these three reservoirs from their bottoms to nominal flow lines is about 600,000,000 gallons. The main pumping station is located at Bryant and Adams streets. In this building are the pumps which supply raw water under high pressure for washing and transporting the sand. These pumps at the minimum lift are guaranteed to deliver 40,000,000 gallons per 24 hours, but they have often delivered 25 per cent, more than the guaranty. The total sum of money appropriated for the cost of the filters was $3,468,405 and the cost of the pumping station was $183,600. The water is pumped direct to the filters and passes thence through regulator houses to a oure-water reservoir holding about 14,000,000 gallons. The pumps were supplied by Henry R. Worthington; boilers by Babcock & Wilcox; the valves by the Coffin Valve Co., and the Venturi meters by the Builders’ Iron Foundry. In the fall the average turbidity of the water as received at Great Falls is & parts of suspended matter in 1,000,000; after filtration 1.3 per month. Each of the filters clarified on an average of 3,000,000 gallons per day. The district pumping station is used for sending water in such parts ot the district as are too high to be supplied directly by gravity from the clear basins of the filtration plant. The equipment consists of two 20,000,000gallon vertical triple expansion engines with double-acting outside-packed plunger pumps operating against a net head of 75 feet; one 7,000,000gallon horizontal triple-expansion engine with double-acting outside-packed plunger operating against a 170-foot head, and one 2,500,000-gallon vertical triple-expansion engine with single-acting plungers operating against 375-foot head. There is also a 12,000,000-gallon vertical engine for 1751’oot head and 30,000,000-gallon vertical engine for 75-foot head.


The sewage pumping station is a concrete foundation and brick superstructure 275 x 125 feet. The engines installed in the building are tripleexpansion with centrifugal pumps comprising eight storm-weather pumping engines with capcitv of 65,000,000 gallons per day; three sewage pumping engines of 65,000,000 gallons per day, and two sewage pumping engines each with a capacity of 20,000,000 gallons daily. These engines are manufactured by the Allis-Chalmers Company at a cost of $253,000. The engines pump 150,000,000 gallons per day, all of which is discharged into the Potomac river.

The high-pressure gravity fire system was designed to utilize water from the Mort Reno reservoir, which is 415 feet above mean tide level. There is a fall of seven miles from this reservoir to the area which it protects. There are four large trunk mains, the main feed being 36 inches with laterals of 25 inches and 12 inches. The hydrants are located not more than 200 feet apart. The area protected is 18 city blocks long and fight blocks wide. As an auxiliary the 26inch main feed pipe is connected to the large pumps in the city pumping station.

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