for settlers you dont want, take away their weapons and send them here
http://fallout.wikia.com/wiki/Murkwater_construction_site
Mirelurk Queen is always around.
I've been building up my dyke colony. Now Sanctuary and the mercer safehouse are a total sausage fest after sending all the bitches to hangmans alley. I'll probably have a queen thin out the herd so the dick to vag ratio is a little more balanced in my other settlements.
Fun fact:
if you give a settler a gun, and 1 round of ammo for that weapon....they will have unlimited ammo.
Arm you guard posts people and have no worries.