I am downright disgusted that this appears to be the first time this "tank" is being searched! I asked earlier if we were sure attics, crawlspaces, washers/dryers were searched? No need for anyone to tell me if these structures are common or not in Tuscon, many have already answered.
There are just obvious places that should be searched. Semaj Crosby was found under a sofa without legs. The Tunstall children were found in the washer and dryer. All children, yet found on subsequent searches in homes they disappeared from!
It should just be common sense to search places like sewers, tanks, buildings, etc in the immediate area, and all enclosed spaces or appliances, etc.