El Dorado Substation

is a power station near HELIOS One and is occupied by the NCR. You are told told by a guard not to enter the building or fenced-in area, though there is no reason to enter the fenced area.

Location
is located southwest of Vault 11 and northwest of El Dorado Dry Lake (which is northwest of El Dorado Gas & Service, a more well-known location). It is to the north of HELIOS One, but twice the distance to HELIOS One than to Vault 11.

Related Quests

 * The Wild Card: Finishing Touch quest requests you to go to this location to upload the Override Chip. If Boone is your companion while you upload the chip he will be disgusted by your actions and you'll never see him again. (In my game (PC) this is not true, he'll even happily start killing the guards inside, plz confirm) This will lower your NCR rep. Entering the building is considered trespassing, if you have a low sneak the guards will tell you to leave and follow you. Even if you have a high sneak there may be someone awake (even at night) to spot you in the small room, so using a Stealth Boy is recommended. Disguising yourself as NCR has no effect and they still treat you as though you are trespassing.