THE BUILDING FOUNDATION 



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BKFOHK beginning construction of the foundation.-*, in order 

 that the engineers might know the exact condition of the 

 soil undernenth tin- -ite of the building, "tot borings" were 

 made by Messrs. Phillips and Worthington in four places, going 

 from 80 to 100 feet below the Broadway curb, not only to the 

 rock but >everal feet into it. Diamond drills were employed to 

 TCCT RADIVTC remove * ne cores which were brought to the sur- 

 face for inspection, which was necessary to prove 

 that the borings had not stopped on a huge boulder deposited by 

 the glacial drift in past ages. These rounded boulders, which 

 abound in the hard pan, are generally of a very much harder stone 

 than the bed rock, which is characterized as New York gneiss or 

 micaceous schist. 



Roughly speaking, from the surface to about 70 feet below t tic- 

 Broadway curb the borings indicated what is known as New York 

 quicksand, a material so fine that it will readily flow wherever 

 water will, and while it will safely carry a considerable load, if 

 confined in such a way that it cannot leak out, it is, of course, a 

 very dangerous material to build on where there is any chance of 

 such a leak. 



Future cross-town tunnels will undoubtedly undermine many 

 buildings so founded in lower New York. Underneath the quick- 

 sand and above the rock was found from 20 to 30 feet of hard 

 pan and boulders, both of glacial deposit. 



In some places this hard pan was almost as compact as good 

 concrete and in others it verged into mere sand or sand and 

 boulders. In fact, it was so irregular that not only was the material 

 found in one caisson no criterion for what might be expected in 

 the adjoining caisson, but even what was found in one end of a 

 caisson differed entirely from that in the other end. 



Though the original portions of the building are carried on a 

 grillage, or spread footing foundation, 24 feet below the sidewalk, 

 and the first intention was to build the Tower on foundations of a 

 similar character, the engineers, in view of possible subway con- 

 struction in the vicinity, decided to adopt the pneumatic caisson 

 type of foundation carried to bed rock, which is here about 90 feet 

 below the sidewalk level. Competitive bids were taken and the 

 work was let to The Foundation Company, which started work on 

 Aug. 28, 1906, and by working continuously night and day handed 

 over the completed foundation March 1, 1907. In view of the spe- 

 cial difficulties encountered this was a very creditable achievement. 



The first difficulty which presented itself, and possibly the one 

 requiring the greatest ingenuity to overcome, was the great area 



covered by the 30 caissons compared with the total 

 , .,' .. ... . ' . 



arca * "ie sl te> which restricted the space remain- 

 . , ., . . .. . , . . 



in S hoisting frames, tackle, run-ways for 



the delivery of material and removal of waste, the 

 compressors and other machinery used in the work. As the new 

 part of the building, though of considerable area, has a frontage of 



[12] 



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