Hazmat disposal site L5 is a system of caves storing radioactive waste that connect L'Enfant Plaza to the Mall. Entrance may be gained through the L'Enfant Plaza Metro tunnels. A hole in the tracks leads you to the cave network below the subway tunnels. Another entrance is located at the southwest corner of The Mall, near the Lincoln Memorial.
The L'Enfant Plaza entrance is a generic, large metro entrance behind the broken pyramid and next to a refrigerator. A number of super mutants occupy the area. The Mall entrance is signified by a large metro entrance near the Lincoln Memorial. No enemies repeatedly spawn in the vicinity of this metro entrance.
Hazmat disposal site L5
Coming from the L'Enfant Plaza entrance, there is a bed located in the back corner immediately upon entering the metro. The disposal site is home to one or two super mutants (near the L'Enfant Plaza exit), and a number of feral ghouls, ranging from basic ferals to glowing ones. At higher levels, with the Broken Steel add-on there will be several feral ghoul reavers. Usually one in the main cavern and one in each of the 3 tunnels.
If you are exiting into L'Enfant Plaza from the Mall be warned it is a serious hotbed of super mutant activity. If you are not cautious it is very easy to be swarmed by 6-10 super mutants including a few super mutant overlords at higher levels with Broken Steel.
The body of a dead wastelander found in the caverns can be seen with their fingers twitching. The body may be animated in sleep mode instead of being animated dead, but isn't actually alive and can be looted normally. However, If you look closely, it appears that there's gas in the area, which causes a shimmering effect, and makes it look like the fingers are moving. Be careful shooting in this area, you will set off the gas.
Hazmat disposal site L5 only appears in Fallout 3.