Here is the full list of all 20 The Brookhaven Experiment achievements.
Blow the head off of something large and toothy.
Acquire 200 throwables in campaign mode.
Acquire all guns and upgrades in a survival game.
Survive ten waves in a survival map.
Survive the final campaign level.
Survive the ninth campaign level.
Acquire all guns and upgrades in campaign mode.
Survive the eight campaign level.
Kill 1000 enemies.
Finish a nighttime campaign level without turning on the flashlight.
Survive a nighttime campaign level using only the knife.
Survive the seventh campaign level.
Survive the sixth campaign level.
Kill four enemies at once with an explosive.
Survive the fifth campaign level.
Survive the fourth campaign level.
Survive the third campaign level.
Kill 100 enemies.
Survive the second campaign level.
Survive the first campaign level.