Boulder Canyon Project Relies on Old and New Power to Pave Ways

During the Boulder Canyon portion of these water projects, old and new technology was used when deemed necessary. It is interesting to note the use of diesel-powered compressors to level grounds for creating highways and pathways for railroads, then opting for older steam-powered locomotives to haul building materials to the dam's construction site. 
The irony is not lost in using the new methods to make way for the old.
Below are pictured the 19th-century style, 90-ton locomotive used in this 1929 report, hauling materials by the car at 50-tons each and the newer diesel compressor that makes new railways possible (both shown as the bottom image on each page).
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NARA Series: Boulder Canyon Project Series, 1948-1966. Record Group 48: Records of the Office of the Secretary of the Interior, 1826-2009. National Archives Identifier: 2292774