A(n) inverted siphon is used to get sewer lines from one side to the other of a creek, river, arroyo, etc.

• A. Culvert
• B. Bridge
• C. Tunnel
• D. Inverted siphon

Answer: (D)

Crossing a creek with a gravity sewer line is often done with an inverted siphon. The pipe goes down on the near bank, under the creek bed, and back up on the far bank, staying full of sewage so gravity drives the flow across the watercourse. This keeps the line continuous and full, avoids exposing a surface opening, and doesn’t require a bridge. A culvert, while it carries water under obstacles, isn’t intended to carry a full, gravity-driven sewer; a bridge would service traffic and isn’t the typical solution for a sewer crossing; a tunnel could be used but is usually more expensive and less specific to this crossing method. The described setup fits the idea of an inverted siphon.