That is a great back and forth split which I will steal but will change one part. On #2 I will have the Sheriff knock on the door and just say there's been an accident. Then cut back to surveyor group. It keeps a little mystery going for both groups and doesn't feel like a pre-destined outcome for the surveyor group. (It's a pet peeve I have learned from my players that REALLY don't like it when a set of actions is going to occur no matter what they do.) This still allows for the other group to come as the rescuers when needed by the survey group.