BOULDER CANYON PROJECT NELSON 449 



a million yards were in place, another million was poured in the fol- 

 lowing half year, and the third million on December 6, 1934, only 

 18 months after the first bucket dumped its load of concrete 700 feet 

 below. Crest height was reached on March 23, 1935, and by the fol- 

 lowing summer all concrete — 3,250,000 yards of it — was in place, 

 with the exception of the filling of temporary galleries. A remark- 

 able record — 1,200 men with modern equipment had in 21 months 

 built a structure whose volume is greater than the largest pyramid in 

 Egypt, which, according to Herodotus, required 100,000 men 20 

 years to construct. 



The contract with Six Companies, Inc. allowed 7 years to complete 

 the work, but by the aid of an efficient personnel, and with the as- 

 sistance of the most modern equipment, the contract is expected to 

 be completed nearly 2 years in advance of the expiration date. Work 

 remaining to be done by the contractor on October 1, 1935, was prin- 

 cipally in the adding of the final touches to major structures, filling 

 the temporary galleries of the dam with concrete, completing the two 

 tunnel plug outlets, pouring concrete piers, anchors and thrust blocks 

 for the plate steel penstock pipe and removing the debris of con- 

 struction. 



New problems arose from the decision to place steel pipes in tun- 

 nels for supplying water to outlet works and power-house turbines. 

 The principal provisions of the contract given to the Babcock & 

 Wilcox Co., of Barberton, Ohio, for its low bid of $10,908,000, were 

 to furnish and place 2% miles of plate steel pipe, whose maximum 

 thickness of steel was nearly 3 inches, and whose gross weight ex- 

 ceeded 44,000 tons. As mentioned, in part, previously, the penstock 

 header lines are 30 feet and 25 feet in diameter, penstocks of 13 

 feet (excepting 108 feet of 9-foot diameter), and the outlet conduits 

 of 86-inch and 102-inch diameter. 



Railroad facilities were inadequate to transport the larger pipe 

 sections, and therefore a modern fabrication plant was built at a suit- 

 able location along the United States construction railroad, 1% miles 

 from the top of the Nevada dam abutment. Flat plates were shipped 

 to the plant and the pipe sections entirely fabricated there. A sec- 

 tion of the largest pipe when completed had a length of 23 feet 4 

 inches and a weight of 175 tons. 



Fabrication of a 30-foot section consisted essentially of marking 

 six 10-foot 6-inch by 31-foot 5-inch flat plates, cutting them to size 

 with an acetylene torch, planing welding grooves on three sides, pre- 

 paring the plates for rolling by bending the ends in a 3,000-ton 

 press, rolling the plates in 12-foot vertical rolls, assembling and 

 electrically welding the plates together and adding butt straps and 

 stiffeners. All welds between the rolled plates were then X-rayed 



