First off, amazing job on putting the map together and locating so many buildings and landmarks!
So I have a question. What do you think the thing I outlined in red could be?
My guess would be the Los Angeles Aqueduct Cascades Facility.
^This link shows off some pictures of the place and here is the google maps link:
Though it is to blury to tell that would be my best guess. Thanks for your time and keep up the great work finding more buildings and land marks!