Interesting. I googled Harquahala Mountain and came up with this:
Atop 5,620-foot Harquahala Mountain is an abandoned astrophysical observatory, built by the Smithsonian Institution in the 1920s to measure solar activity. It’s listed on the National Register of Historic Places. There’s also a modern Central Arizona Project facility that’s used to manage the canals running from the Colorado River. 
Do you suppose the buildings and other stuff may have been part of that observatory? Did you see evidence of anything mentioned about the CAP?