That's where this side quest comes into play.
And as you speak to Monroe, you'll realize that he could really use your help. One of the only people you'll find that you can speak with is named Lieutenant Monroe.
When you arrive at Boulder City, you'll find that the town is extremely dilapidated, even more-so than many of the other towns, villages and settlements in the Mojave Wasteland. You'll have to head there from Novac (which is southwest of Boulder City) in order to finish your task off. Boulder City is located far to the east of Goodsprings. During the end of the main quest known as They Went That-a-Way, you'll have to travel over to a location known as Boulder City. This is yet another side quest that's intimately intertwined with the game's main mission as chronicled in our gigantic Walkthrough. (1) Help the NCR kill all the Great Khans up in the Boulder City ruins. Side Quests Index Boulder City Showdown (Official)