CHAPTER Xril 

 GEOLOGICAL CONDITIONS AFFECTING THE LOCATION OF 

 DELIVERY CONDUITS IN NEW YORK CITY 



Hill View reservoir is the terminus of the Southern aqueduct. 

 The Catskill water is to be delivered at this point, just north of the 

 Xew York city line on the Yonkers side, at an elevation of 295 

 feet. From this reservoir the water is to be distributed by an inde- 

 pendent system of conduits to the principal centers of consumption 

 in lower ^Manhattan and Brooklyn. 



It is believed that distribution can be most economically made 

 and the system be most permanently established by constructing 

 the main trunk distributaries as tunnels in solid bed rock at con- 

 siderable depth below all surface disturbances. 



Preliminary investigations have been carried on by Headquarters 

 department. ]\Ir Alfred D. Flinn, department engineer, beginning 

 in 1908. As the active work of exploration was entered upon ]\Ir 

 William A\'. Brush, department engineer, was assigned to this special 

 division of the department's work and most of the preliminary ex- 

 ploration borings wxre planned and finished under his immediate 

 supervision. With the resignation of ^Ir Brush to take the post 

 of deputy chief engineer in the Department of Water Supply, Gas 

 and Electricity, Mr Walter E. Spear, department engineer, was 

 secured to continue the difficult work of finishing explorations and 

 preparing for construction. 



Studies of conditions affecting such a system and explorations 

 designed to test the ground ifi line with these studies^ have been 

 made. The work thus far done in an exploratory w^ay has been 

 confined to one main distributary. 



Section A. Preliminary geological study 



As a preliminary step toward the systematic study of local con- 

 ditions affecting possible conduits, trial lines Avere laid out on the 



1 Few engineering enterprises, probably, have been planned with so care- 

 ful regard for all known geologic conditions. The geologist and the en- 

 gineer worked alternately on the same problems until, in the opinion of both, 

 the best possible line was selected. It is the writer's belief that so sys- 

 tematic a method has seldom if ever been carried out in engineering work 

 of this kind. On this account, and in part to illustrate some of the pre- 

 liminar>' stages in such work, many of the original facts and arguments 

 and suggestions are given without change in the following discussion. 



215 



