The Intermountain Power Plant provides energy to many different places. Replacing generation there keeps transmission lines balanced as they were. Wikipedia sa

The Intermountain Power Plant provides energy to many different places. Replacing generation there keeps transmission lines balanced as they were. Wikipedia says LADWP operates 4 natural gas power plants within city limits, so they do both. It might be hard to find a site for a new generator, and the Intermountain site had additional coal generators planned but not built; building a natural gas generator there makes a lot of sense.