CHAPTER VI 

 THE RONDOUT VALLEY SECTION 



Because of the fact that the hydrauHc grade of the Catskill aque- 

 duct as it approaches the Rondout valley is nearly 500 feet A. T., 

 an elevation more than 300 feet above the lowest portions of the 

 valley and more than 200 feet above very large areas of it, a total 

 width of more than 4 miles being too low for unsupported con- 

 struction of some kind, and because of the general policy of using 

 the pressure tunnel system so as to deliver the water at a corre- 

 sponding elevation on the east side of the valley, and further 

 because of the very complicated geological features of the district 

 this section has been the seat of very extensive and interesting 

 explorations. 



Undoubtedly a greater number of obscure features occur here 

 than on any other single section of the whole aqueduct line. Most 

 of these features are readable from surface phenomena in general 

 terms. In all cases the indications are plain enough to serve as a 

 guide to well directed tests, but many points of critical importance 

 can not be determined with sufficient detail and accuracy of posi- 

 tion for such an engineering enterprise without systematic explora- 

 tion.^ The basis and results of this line of investigation which has 

 occupied the greater part of two years are summarized and plotted 

 in the following discussion and , charts. The portion receiving 

 special study is in the vicinity of High Falls. 



General geology 



Almost everywhere the surface is glacial drift. Where outcrops 

 of bed rock occur they habitually present the unsymmetrical ridge 

 appearance usually with a more or less sharply marked escarpment 

 on one side and a gentle slope on the other. The strike of these 



1 These explorations belong to the Esopus division of the Northern 

 Aqueduct Department. The earliest reconnaissance was done under the 

 direction of James F. Sanborn, division engineer, who was subsequently 

 assigned to geologic work over a con iderable portion of the Aqueduct line. 

 The development of exhaustive explorations and final construction on this 

 division has been carried on under Lazarus White, division engineer, 

 assisted by Thomas H, Hogan. The division has been recognized from 

 the beginning as an important one and in many ways one of the most com- 

 plex. Thomas C. Brown, now professor of geology in Middlebury College, 

 was employed for a year on this division during the later exploratory work. 



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