The scenes in Abilene, TX used for the underground base were actually filmed at the decommissioned Valhalla Missle Silo. It is now used as a deep water diving certification facility and is owned and operated by Mark and Linda Hannifin of Family Scuba Center in Midland, TX.
All the FX props and CGI were created by Tomas "Twiggy" Ramirez the Director of Photography.