EnPro Plant
The EnPro plant (short for energy processing plant) provides the primary power to the Communications Facility and backup power to the entire Mars UAC base. The EnPro plant houses the main plasma reactor, and plenty of plasma guns and ammunition, which were created in this facility by researcher Theresa Chasar.
The only known entrance is from Alpha Labs. Exits exist to Communications Transfer and to the Mars City Service Sub-Level area (as a retcon introduced in The Lost Mission only).