You see, the picture that gets painted here is that if a limit that low were put on the passage of products to the communities, you would need to make a separate trip to each community, as opposed to having a facility where you could service two or three, or maybe even four communities in one run.
The concern I would have is that the limit you're suggesting would in fact increase the number of ship movements in the area. Of course, with the increased movements comes increased risk.