GEOLOGY OF THE NEW YORK CITY AQUEDUCT 



147 



three days after pumping ceased water rose 5.2 feet, and in 22 days 

 rose 9.8 feet or at the rate of 0.45 feet per day. 



During construction^ shaft 4 located at same point as hole 32/22, 

 station 607 + 50, has proved a very wet shaft, the inflow varying 

 from 400 to 850 gallons per minute. Pumping at this shaft has 

 lowered the general water level and correspondingly lowered the 

 water level in hole 34/22 at station 600 + 00. 



Fig. 26 Curve showing rise of water in holes 32 and 34 after pumping ceased in hole 34 



1 From this shaft after reaching tunnel grade, — 250 feet, and after running 

 northward into the fault zone and porous shales, the contractors are pumping 

 1300 gallons per minute. 



