ZOOM IN ON POWER PLANT
You sure that’s it?
I don’t think that is THE plant. There is no construction activity, no parking lots, site prep nothing. Try
a couple of miles south. This appears to be a 16 gas turbine combined cycle, natural gas fired plant. I started one of these up, many years ago, but half the size. Looks like de-mineralized make up water tanks to the east. They could have been doing steam blowing. I had a close call myself with super-heated steam through a gasket on a flange that was not tightened properly. No way could this be an H2 explosion. There’s only a limited number of H2 bottles and it is not needed unless the plant is approaching full power.
These plants are sometime auxiliary fired to superheat and dry the steam generated from the GT’s exhaust. This is the only process I know where a large volume of combustible vapor would exist. Perhaps this process failed and blew up. Unless there was a catastrophic gas main failure that filled the entire steam cycle building and ignited before source could be shut off. That explosion could injure many persons during a construction/start-up milestone activity day.
I think that it's the area to the west of your location. See this absolutely ugly graphic I threw together in a rush, with credit to Google Maps for the image:
Also, look at bing.com's Bird's Eye View of the plant. That's not the same one.