The St. Neal Energy Plant was a Combine energy plant that was destroyed by Gordon Freeman and MacCready's team of rebels.
The energy plant was guarded by a MP Force of Combine known as the St. Neal MP Force. The MP Force was basically a large group of Combine soldiers who guarded the plant and failed during MacCready's attack.
It was directed by Frederick Mason, a Combine officer.
The St. Neal Energy Plant was designed to circulate energy and provide it to the cities and to Combine bases. The base was surrounded by several drills and solar panels. There are also multiple generators inside of the base.