The New York Rapid-transit Subway

Proceedings.] PARSONS ON NEW YORK RAPID-TRANSIT SUBWAY. 47 Company on a lump-sum basis, and sub-contracted on a unit basis. In these sub-contracts the cost of excavation varied greatly, according to the locality and the facilities for doing the work. In the least populated districts, where the streets were wide and work could be carried on without interruption, the cost per cubic yard for excavation in sand ranged from 70 cents to $33.50, and in rock from $2 to $6.25. The cost rose to $6 per cubic yard for the earth in lower Broadway, with a very heavy and congested traffic above, which had to be borne by a timber roof. The cost of tunnelling in rock ranged from $4.50 per cubic yard to $10 per cubic yard. Concrete in place, including the necessary forms, varied from $8 to $12 per cubic yard, and the steel cost from $80 to $90 per ton (2,000 lbs.) in place. The total quantities of the major items handled were:—- Structural steel Rail-steel. Cast iron . Excavation : Rock „ Earth Tunnelling Waterproofing Cement Concrete . Tons (2,000 lbs.) 97,500 . Tons (2,240 lbs.) 12,600 . Tons (2,000 lbs.) 38,000 . . Cubic yards 925,000 ...„ „ 2,700,000 . . . „ „ 515,000 Square yds. 1,100,000 . . . . Barrels 1,320,000 . . Cubic yards 725,000 Accidents. Besides minor accidents, which are inseparable from a work of this magnitude, there were but two of serious character. One was an explosion of dynamite, caused by the carelessness of a workman, and the other was a slip in one of the Murray Hill tunnels. At the point where the latter occurred, borings indicated hard rock. The tunnel-heading had been driven some distance beyond the point and had been widened to the full width of the tunnel, and the bench was in process of excavation. The rock was hard, firm, and required vigorous blasting for its removal. All indications pointed to perfect safety. Unfortunately there was a fault in the rock not determinable from the interior of the tunnel. This fault left but a thin shell of rock on the side nearest the houses, the plane of the faces of which was but 10 feet away, measured horizontally, from the side of the tunnel, the bottom of the tunnel being about 60 feet beneath the surface of the street. This thin shell of rock slipped inward along a seam, the dirt behind it fell into the tunnel, disturbed the founda- tions of three houses at the side, and brought down their front walls. Fortunately no personal injury occurred. For a distance of nearly