Engineering Wonders of the World
Volume III

THE WATER SUPPLY OF NEW YORK CITY. 109 through that city and below the Narrows to Staten Island, the water wants of these por- the rock, and having a circular waterway about 141 feet in diameter. tions of Greater New York should be fully Before the line was definitely laid down, a provided for. Altogether, the territory covered by the new water supply, measured careful study was necessary, first on the maps of the United States Geological Survey, and then in the field, of all only by the main aqueduct and main conduit line, from the head of the Asho- kan Reservoir to the terminal reservoir on Staten Is- land, extends J® 125 miles. Attention Å FULL-SIZE SECTION OF CUT- AND-COVER CONCRETE TYPE, CATSKILL AQUEDUCT, ERECTED IN THE TESTING YARD AT NEW YORK CITY. routes which showed any promise of being feasible. In this connection, it is L interesting to note that the extreme lines crossed the Hud- k son River over 20 miles ‘and apart, that IS must here be called to the extraordinary dimensions and characteristics of the new aqueduct as an engineering structure. Wher- ever possible, the conduit is A Colossal bejng built of concrete and Enterprise. . . m open cut, with a horseshoe section of 17 feet high by 17J feet wide—or 3 J feet higher and 4 feet wider than the normal section of the New Croton Aqueduct tunnel. The tunnels on the hydraulic gradient will also have a height of 17 feet, but, con- sequent on the greater slope allowed, the width is reduced to 14 feet 4 inches. Else- where, valleys and rivers have to be crossed by pressure tunnels below grade, cut deep in 57,000 acres were covered by the topo- graphical surveys. The ideal route, of course, would have been a straight one, along which the aqueduct could be constructed in open cut on the hydraulic gradient. As this was out of the question, the engineers directed their attention to securing, without undue increase in the length of the line, the smallest percent- age of tunnel and siphon. How far they suc- ceeded will be seen in the following table :— Distance between Ashokan Reservoir and Croton Lake.......................... 54 miles. Aqueduct at grade in cut-and-cover...36'35 ,, 60% Aqueduct at grade in tunnel.......... 6’66 „ 11% Aqueduct below grade in siphon.......17'25 „ 29% Total..............60’26 miles.