Four guy derricks (50 to 80-ft. masts and 45 to 60-ft. booms), operated by Lambert 7 by 10-in. engines, with two drums and swinging gear, mounted with 25-h.p. vertical boilers, but driven by compressed air.
Seventy Ingersoll-Rand rock drills, Nos. 1, 3¼, and 4.
Two Rand quarry bars, cutting 10 ft. in length at one set-up, and mounted with No. 4 drill using a Z-bit.
Twenty-one H. K. Porter locomotives, 10 by 16-in., and 36-in. gauge.
Three Davenport locomotives, 9 by 16-in., and 36-in. gauge.
One hundred and forty Western dump-cars, each of 4 cu. yd. capacity.
One hundred and sixty-five flat cars, with iron skips, each of 4 cu. yd. capacity.
Four stiff-leg derricks on extension, having 35-ft. masts and 40-ft. booms, and each operated by a 60-h.p. Lambert, three-drum, electric, hoisting engine.
One stiff-leg derrick, on the south side of the pier on the upper deck, with a 28-ft. mast operated by a three-drum Lambert engine and a 25-h.p. vertical boiler.
One stiff-leg derrick, on the north side of the dock on the upper deck, used exclusively for bringing in brick, electric conduit, pipe, and other building material, operated when first erected by a three-drum, steam-driven, Lambert, hoisting engine. This engine was later changed to the derrick on the south side of the dock, and a motor-driven Lambert engine from that derrick was substituted.
One stiff-leg derrick, previously used in retaining-wall work.
One Smith concrete mixer, 1 cu. yd. capacity, driven by attached air engine.
Two cableways taken from the retaining-wall plant and used for mucking out the tunnels after the center pier had been built; driven by air supplied to the original engine.
One Robbins belt conveyor, driven by a 30-h.p. engine run by air.
Ground was broken for work under the principal contract on July 9th, 1904, on which date the contractor began cutting asphalt for Trench No. 1 in 31st Street, and also began making a roadway from Ninth Avenue into the pit just south of 32d Street.
_Excavation for Retaining Walls._--Two essentially different methods were used in excavating for and building the retaining walls; one, construction in trench, the other, construction on bench. In general, the trench method was used wherever the rock on which the wall was to be founded was 12 ft. or more below the surface of the street; or, what is perhaps a more exact statement, as it includes the determining factor, where the buildings adjoining the wall location were not founded on rock.