Chasm

Nearby the rear entrance to the
Black Mesa facility, a deep chasm
rips between abandoned missile
bunkers from the old base.  When
the soldiers attacked, a group of
civilians holed up in the West
bunker helping themselves to the
arms and supplies there.
Unfortunately, the soldiers had
been using the East bunker as a
command post. During the
unavoidable battle, the soldiers
(intent on eradicating the civilians
who knew too much) were in danger
of being eradicated themselves by
the newly armed Black Mesa refugees.