There are a total of 25 Freak Breaches found in Pacific City. Once you detonate a beacon, a Freak Breach will appear in the vicinity. Freak Breaches are found by their yellow markers. They can only be accomplished at night. The best weapon to quickly get rid of them is by using the UV Shotgun at large groups and once there is a huge cluster of them, throw grenades/use explosive weapons. Once you have killed all of the enemies, a helicopter will come and close the hole. This counts as closing a Freak Breach.