At long last, the dozer will be at my place as soon as it is dry enough to run...perhaps this week! I have built a number of gray PVC structures that I intend to place in the pond once it is dug. For the most part, these structures are about 4'-5' tall, and about 3' in diameter.

My question is how deep to place them. It seems to me that I would want the top of these structures about 4' below the surface. Does that sound right?