342 THE WASHINGTON AQUEDUCT 



The total length of the conduit and the two by-conduits 

 around the reservoirs is 12 miles, and its slope is nine inches in 

 5,000 feet. Constructed by General Meigs in connection with 

 the aqueduct system are five bridges, two of which are unic^ue 

 among engineering structures and will be brief! 3"^ described later. 



At the distributing reservoir the water passes into four cast- 

 iron mains — 48 inches, 36 inches, 30 inches, and 12 inches in 

 diameter respectively. The Dalecarlia reservoir has a storage 

 capacity of about 150,000,000 gallons, is ])ractically without 

 paved slope-walls, and is perfectly protected against pollution 

 from the drainage of the surrounding country. The distrilniting 

 reservoir has a storage capacity of about 150,850,000 gallons and 

 is divided by a puddled and paved wall (through which is a 

 passageway) into two sections containing 97,600,000 and 

 53,250,000 gallons resi)ectively. The Georgetown high-service 

 reservoir has a capacity of about 1,500,000 gallons. 



In addition to the three reservoirs already mentioned, which 

 form a part of the aqueduct system, there is another reservoir, 

 built and controlled by the Commissioners of the District of Co- 

 lumbia, called the Fort Reno reservoir, with a capacit}^ of about 

 4,500,000 gallons, tlie reference of its water surface when the 

 reservoir is full being about 420 feet above mean tide at the 

 navy yard. 



The Dalecarlia and distributing reservoirs supply the ])umping 

 station and that part of the District which lies below 100 feet 

 above datum. The areas bnng between the levels of 100 and 210 

 feet above datum are supplied by pumping from the U-street 

 station directl}' into the distributing mains, the Georgetown high- 

 service reservoir being held as a reserve supply. The areas liav- 

 ing a greater elevation than 210 feet above datum are supplied 

 from the Fort Reno reservoir. It will be observed, therefore, that 

 the total present storage capacity of all reservoirs is a little less 

 "than 307,000,000 gallons, or about six days' snppl3^ 



In July, 1897, for the first time in its history the conduit was 

 permitted to discharge its maximum flow, which by current meter 

 observations \vas found to be 76,500,000 gallons per 24 hours. 

 Today the average daily consumption is about 45,000,000 gallons, 

 or about 60 per cent of the ultimate capacity of the conduit. Ten 

 years ago it was but 35 per cent, or less than 27,000,000 gallons. 



To avoid misapprehension it should be stated that while the 

 conduit can sui)ply the distributing reservoir with 76,500,000 

 gallons per day, yet the pipes leading from the reservoir to tlie 



