BOULDER CANYOK PROJECT — NELSON 445 



nearly a thousand dwellings comfortably housed the town's 5,000 

 persons. 



Highways and railroads were built from main lines across 30 

 miles of desert to canyon rims. Other roads were constructed and 

 rails laid to the bottom of Black Canyon and to various construc- 

 tion plants. Boats and barges first carried men and equipment on 

 the river, but these were replaced early in construction by steel 

 bridges and a group of cableways. Materials were required in quan- 

 tities never before sliipped to a single construction job in such a 

 short time— 5,000,000 barrels of cement; 8,000,000 tons of sand, 

 gravel, and cobbles; 45,000,000 pounds of reinforcement steel; 18,- 

 000,000 pounds of structural steel; 21,000,000 pounds of gates and 

 valves; and 840 miles of pipe were hauled over the railroads in 

 the first 4 years of construction. On many days GO cars of materials 

 arrived on the project, and the total number of cars received in 

 Boulder City from plants throughout the Nation amounted to more 

 than 30,000, which figure does not include the 145,000 cars of sand, 

 gravel, and cobbles placed in concrete construction. 



Even as the structures at Black Canyon were required to be the 

 greatest of their kind ever built, so were many of the plants and 

 much of the equipment used in construction, the largest of their type. 

 Trucks were provided with aluminum bodies, capable of hauling 

 16 cubic yards of materials, others were of 50-ton capacity, and some 

 were converted into 100- and 150-man transports. Air compressor 

 plants of 14,500 cubic feet per minute capacity were built near the 

 river's edge. A 20-mile railroad, whose rolling stock included 29 

 steam and electric locomotives, was laid to connect all construction 

 plants on the project. 



Transportation of men and materials between canyon walls or 

 from rim to river channel was accomplished in great part by the 

 use of cableways. The first of these were small 8-ton installations 

 whose track cables were fastened in concrete-filled tunnels in the 

 canyon walls, but the five that were used primarily for placing 

 concrete in the major features of construction were of 25-ton nomi- 

 nal capacity and of movable end tower type. Both of the end struc- 

 tures, or towers, of four of these and the tail tower of the fifth, 

 to which the track cables were fastened, consisted of heavy struc- 

 tural steel frame works mounted on rails. The head and tail 

 towers of the two largest cableways, whose spans were nearly a half 

 mile, were 90 feet in height and the distances between center lines 

 of front and rear tracks for each tower were 46 feet. The over- 

 turning moment from the cable and its load was counteracted pri- 

 marily by a million-pound block of concrete placed over the rear 

 tracks and by centrally located trucks which traveled against a rail 



