CHAPTER II 

 PROBLEMS ENCOUNTERED IN THE PROJECT 



When the Ashokan reservoir is filled the surface of the stored 

 waters will stand 590 feet above the sea. Hill View reservoir on 

 the northern borders of New York city will have an elevation of 

 295 feet. The distance between these two points is nearly 75 miles 

 in direct line. The contour of the country and other exigencies 

 of construction will increase this to approximately 92 miles. A 

 main distributary conduit in New York city will add 18 miles more. 



The destination of the water therefore before distribution begins 

 is 300 feet lower than its starting point. This is sufficient head to 

 permit gravitational flow and a self-delivering system. If the hy- 

 draulic gradient can be maintained it would evidently constitute a 

 decided advantage. The plans have therefore from the beginning 

 contemplated such construction. It means then that a flowing 

 grade must be maintained in all tunnels or channels or tubes and 

 that when a depression has to be crossed the pressure must be 

 maintained in some sort of a conduit so that the water may rise 

 again to a suitable level on the other side. 



The difficulties of accomplishing this in a work of such magnitude 

 are not at first apparent. The full significance of the undertaking 

 can be realized only after a study of the country through which the 

 aqueduct must be carried. It then resolves itself into a series of 

 problems, each one having its own characteristics and peculiar 

 difficulties and methods of solution and each requiring a thorough 

 understanding of the topographic features of the vicinity and a 

 working knowledge of geologic conditions. 



General questions 



It is sufficient at this point to call attention to the facts of the 

 topographic map and point out only the most general physiographic 

 features that may at once be seen to materially modify the simplicity 

 of the line. 



For example, one has scarcely left the great reservoir, with water 

 flowing at 580-90 feet above tide, before the broad Rondout 

 valley is reached, with a width of 4% miles nowhere at great 

 enough elevation to carry the aqueduct at grade. If it is to be 

 crossed at all, and it must be crossed to reach New York city, some 



C17] 



