rdfx:
seen that elbow set done with tile spade or post hole digger, too. hole cut back into bank at water level, and one down from top of bank to link up with other hole. Supposed to be a good water-fluctuating set if you block lower hole with a #110. Haven't figured out good way to block upper hole...but most rat bank den air holes look like this set and the upper hole is mostly an entry point anyway. if the hole goes all way through to lower hole, the mink will follow it on out. lot of work to dig this set out, though. I like your concept of PVC with elbows instead....light, fast setup, white color for eye appeal.
I have some 5' sections of 4" black corregated drain tile, and now you have my wheels a turnin' on using them instead for this setup....
Jim-NE