Testing Hoover Dam’s outflow jets

The San Diego Air And Space Museum posted some wonderful old aerial pictures of Hoover Dam on Flickr, and I’m hoping someone in the Inkstain posse can help me sort out the history. This image was taken by Colonel Orie W. Coyle, and appears to be a test of Hoover Dam’s outlet jets that I’m thinking must have been in the 1930s, as the then-Boulder Dam was first being filled:

Aerial View of Hoover Dam, Col. Coyle served with the Marines in WWI and worked for Douglas prior to his service in WWII, Col. Coyle served with the Marines in WWI and worked for Douglas prior to his service in WWII, courtesy SDASM

Aerial View of Hoover Dam, Col. Coyle served with the Marines in WWI and worked for Douglas prior to his service in WWII, Col. Coyle served with the Marines in WWI and worked for Douglas prior to his service in WWII, courtesy SDASM


It must have been quite a spectacle. You can see the road lined with cars. The UNLV library has some similar pictures including this one, which is dated “1934-1936”. Anyone know the story?