Someone on the Livermore version of NextDoor posted yesterday that there was a helicopter hovering in the south part of town and that they wanted to know if anyone knew what was up. As usual the brighter minds of Livermore had the usual "government helicopter" conspiracy theories so I decided to take a look at the ADSB data I'd collected to see if there were any helicopters in it. I'd never tried looking specifically for helicopters, so I just skimmed the ID list and checked out everything that didn't match a prefix for a known airline (eg, SWA for Southwest). That turned up N404AJ, a twin-rotor Chinook operated by Billings Flying Service that's been helping put out the fires south of Livermore.
It looks like the helicopter left the area yesterday to fight the new fire near Fresno, but these two tracks I captured show how they've been using Livermore as a staging ground to fight fires south of town. They've been landing near Poppy Ridge at Meadowlark Field, which also happens to have a giant Star Wars Rebel Alliance symbol in the field next to it.
Looking around the web some more, I found some photos of the helicopter and the video at the top of this post about how BFS contracted someone to build a tank module so they can dump fire suppressant on fires. So no, tin-foil-hatters of Livermore, not a secret Government operation- just fire fighters protecting your McMansions.