Problem(s) Encountered:

All of the dorm showers are filled with/backed up with brown water. It appears to get higher when the toilets are flushed. 

Solution:

Line was snaked out.  Took some doing but finally broke through the clog.  Septic tanks (at both facilities) were also drained about one week later.  

It should be noted that this issue coincided with a large group visiting the telescopes.  There were more heads than beds for this program.  Our old plumbing is not well-equipped for such rigorous demand.