May I jump in this discussion, please.

Midden, by definition is considered a dump or waste  (pit, trough, etc.)
Specific types of middens are labeled as to their purpose (kitchen 
midden, trash, burned rock) or what materials are the main 
ingredients. Privy is not considered a midden, in my opinion, but a 
privy or septic.

The flume area should, again in my opinion, be considered a feature 
or lens such as a shell lens. The discussion is interesting. I am 
curious to see the possible conclusions.

David Parkhill