Popular Science Monthly 



rial is quicksand. William Street is a 

 narrow winding lane of old downtown 

 New York. It is barely forty feet in 

 width between building fronts, and in 

 the half-mile section where the subway 

 is being dug (from Beekman Street to 

 Pearl) it bears twenty buildings of from 

 seven to twelve stories in height, and ten 

 of from thirteen to twenty stories. When 

 the digging was first proposed, owners 

 of abutting property assessed at forty 

 million dollars protested and carried the 

 case into court. The Public 

 Service Commissioners had 

 so much confidence that the 

 work could be done safely 

 that they assumed responsi- 

 bility for any damages that 

 might result. 



BuUdiug on IVafer 



"The conditions encoun- 

 tered are unique," writes 

 John H. Aladden, Asst. Di- 

 v^ision Engineer, "in the num- 

 ber of large and heavy build- 

 ings, few of which have 

 foundations to rock or hard- 

 pan, and with these excep- 

 tions all other foundations 

 are abo\-e the subway sub- 

 grade and uniformly above 

 water level as well." The sub- 

 way's floor is, in general, 

 three to five feet below mean 

 low water ; and below ground 

 water level the material is 

 swimming sand. ''To guard 

 against any possible flow of 

 material into the subway 

 trench, continuous bulkheads, 

 either in the form of rigidly 

 held, tight sheeting or con- 

 crete cut-off walls, will be in- 

 troduced between the under- 

 pinning piers so as to form an 

 integral portion of the latter 

 and will be carried to such 

 depth below the subgrade of 

 the subway as to eliminate 

 any tendency of the quick- 

 sand to flow under the toe 

 and be released into the ex- 

 cavation," The total esti- 

 mated ccst of the section is 

 two million, two hundred 

 fifty- four thousand, six hun- 



331 



dred and seventy dollars, of which six 

 hundred and four thousand, five hundred 

 dollars is for underpinning. 



William Street is not the only place 

 where the subway diggers have to be 

 particular about building stanch floors 

 and sidewalls. At Broadway and Canal 

 Street an underground watercourse was 

 encountered and a very heavy floor had 

 to be built to resist the water's upward 

 pressure. Pumps with a capacity of 

 twenty million gallons a day were kept 



One of the serious difficulties often met by the engineers. 

 Underground water is seeping into the tunnel near the 

 corner of Broadway and Canal Street so fast that a set 

 of pumps removes twenty million gallons a day from this 

 one spot. The flooring here is reiinforced to resist the 

 upward pressure of the water and quicksand 



