![File:Looking upstream toward Boulder dam site showing outlet portals of all four diversion tunnels. Flow of Colorado... - NARA - 293890.jpg - Wikimedia Commons File:Looking upstream toward Boulder dam site showing outlet portals of all four diversion tunnels. Flow of Colorado... - NARA - 293890.jpg - Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/4/45/Looking_upstream_toward_Boulder_dam_site_showing_outlet_portals_of_all_four_diversion_tunnels._Flow_of_Colorado..._-_NARA_-_293890.jpg)
File:Looking upstream toward Boulder dam site showing outlet portals of all four diversion tunnels. Flow of Colorado... - NARA - 293890.jpg - Wikimedia Commons
![File:Looking upstream into Black Canyon toward Hoover Dam site showing outlet portals of four diversion tunnels and... - NARA - 293789.jpg - Wikimedia Commons File:Looking upstream into Black Canyon toward Hoover Dam site showing outlet portals of four diversion tunnels and... - NARA - 293789.jpg - Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Looking_upstream_into_Black_Canyon_toward_Hoover_Dam_site_showing_outlet_portals_of_four_diversion_tunnels_and..._-_NARA_-_293789.jpg/1200px-Looking_upstream_into_Black_Canyon_toward_Hoover_Dam_site_showing_outlet_portals_of_four_diversion_tunnels_and..._-_NARA_-_293789.jpg)
File:Looking upstream into Black Canyon toward Hoover Dam site showing outlet portals of four diversion tunnels and... - NARA - 293789.jpg - Wikimedia Commons
![Outlet works on the Black Canyon walls Nevada side Hoover Dam Nevada and Arizona USA Stock Photo - Alamy Outlet works on the Black Canyon walls Nevada side Hoover Dam Nevada and Arizona USA Stock Photo - Alamy](https://c8.alamy.com/comp/ATE1MF/outlet-works-on-the-black-canyon-walls-nevada-side-hoover-dam-nevada-ATE1MF.jpg)
Outlet works on the Black Canyon walls Nevada side Hoover Dam Nevada and Arizona USA Stock Photo - Alamy
![Film transparency of Hoover Dam outlet works, circa mid 1930s - Photograph Collections (1 of 2) - Welcome to UNLV's Digital Collections Film transparency of Hoover Dam outlet works, circa mid 1930s - Photograph Collections (1 of 2) - Welcome to UNLV's Digital Collections](https://d.library.unlv.edu/digital/api/singleitem/image/pho/2457/default.jpg)