I built several wetlands that they wanted pipes installed laying on the original grade in the deepest part of the dam and extending out from the dam several feet.
Believe it was 6" (maybe 8") pvc.
After I finished they installed a 90 degree gasket type elbow and a stand pipe to the pipes I had installed.
To drain a wetland they have to get wet, but just push the riser (stand pipe) over.
The gasketed 90 allows the elbow and riser to rotate a 1/4 turn so the top of the riser lies on the bottom draining the wetland.
