A colleague works in a closed (no public access) watershed and came across this culvert today. These smooth "tracks" down the center of the culvert are something we have never seen before. Any idea what they may be for?
Some details that may afford clues:
- Culvert installation date is unknown (so 30+ years).
- The culvert runs underneath an access road.
- There are no other utilities or structures anywhere near (within a mile) of this culvert.
- The channel upstream and downstream of the culvert are still in their natural state.
- Logging use to occur in the watershed in the past, but there are no known logging zones next to this culvert.
- The culvert is massively over sized (serves an area of 150 acres which typically does not receive significant snow-pack).
- This stream empties into a main tributary which is about another 1/3 mile downstream.
- Surface road was originally used for access to the upper part of the watershed, and for logging vehicles/equipment.
- This culvert is located near Portland, Oregon