SUBTEERANEAN EIVER WALKER AND BOND. 



713 



reach rock b}^ the scow drills, two series of inclined borings were 

 made from each shore, one pair intercepting at about 900 feet depth 

 and the other at about 1,500 feet. Both showed satisfactory rock; 

 and accordingly a shaft was sunk on each shore to a depth of ap- 

 proximately 1,100 feet, and then a horizontal tunnel was driven con- 

 necting the two. It is of interest to note that because of the enor- 

 mous head, which must be measured from the flow line far above 

 the river surface, the pressure in the horizontal tunnel reaches over 

 40 tons per square foot. 



OlOji abmfloa Km- 



-34^ 



OLIVE BRIDGE OANI 

 MAXIMUM MASONRV SEOTlOB 



12' '^Half section gt Joint-holes showa. 

 dottetf. 



STEEL PIPE SIPHON 



KENSICO RESERVOIR. 



Next to Ashokan the most important basin is the Kensico reservoir, 

 which lies east of the Hudson, and is situated 30 miles north of the 

 city hall. It will hold sufficient of the Catskill water to supply the 

 city for several months. Its purpose is to act as an emergency 

 storage reservoir, so that if it is necessary, on account of accident, 

 to interrupt the flow in the 77 miles of aqueduct between Kensico 

 and Ashokan, this can be done Avithout interrupting the city supply. 

 The cost of this work is $8,500,000. 



The reservoir will be formed by a huge masonry dam across the 

 valley of the Bronx River. The surface of the water will be at an 



