CHAPTER XII 

 CROTON LAKE CROSSING 



It is proposed to finish Ashokan reservoir and the Northern aque- 

 duct first. This so called Northern aqueduct reaches from the Cats- 

 kills to Croton lake. Croton lake is the present supply of New 

 York city and is already connected by two aqueducts with the city 

 distribution. As a first step, therefore, and as an emergency meas- 

 ure tlie Catskill water will be delivered to the Croton system by 

 finishing the Northern aqueduct first. As rapidly, however, as the 

 whole project can be carried out the so called Southern aqueduct 

 will be constructed to continue the Catskill water independently of 

 the Croton supply to the city. 



The Southern aqueduct department has charge of the line from 

 Hunters brook on the north side of Croton lake to Hill View reser- 

 voir near the New York city boundary. During exploratory work 

 it has been under the direction of Major Merritt H. Smith, depart- 

 ment engineer, with headquarters at White Plains. Construction 

 now going on is in charge of Mr F. E. Winsor, department engineer. 



The first link in this southerly extension is to be a tunnel be- 

 neath Croton lake through which the Catskill water may pass in the 

 same manner as it crosses other valleys. This crossing has been 

 located a short distance below the old dam on the Croton, about 5 

 miles up stream from the Hudson. 



The problems involved at this point include (i) a determination 

 of the kinds and quality of rock to be penetrated, (2) their water- 

 carrying capacity, and (3) opinion as to the proper depth for a 

 successful tunnel. 



Geological features 



The Croton valley is one of the very few in southeastern New 

 York that actually crosses the geological formations and major 

 structural features instead of following parallel to them. In its 

 lower portion it passes from gneiss to limestone and to schist sev- 

 eral times. The reason for this somewhat abnormal course is prob- 

 ably the development of weak zones by fault movements in this 

 transverse direction. 



Only one of the well known formations of rock is exposed in 

 the immediate vicinity of the tunnel site. This is the Manhattan 

 schist, the uppermost formation of the regio-n south of the High- 

 lands. Along the Croton it varies greatly, the chief type being a 



183 



