Ok, attached are four principle ways I can think of to drain my pond. I think the siphon system is out due to shallow grade attainable for the outlet pipe.
A CMP standpipe system is what the landscape architect designed, but materials & labor for this system is $8-10k, which seems a little crazy for a backyard pond with a 100-120ft run of buried pipe (some of the cost I'm stuck with, including the pipe run and tapping into the nearby storm drain). Of course the shrouded standpipe option - or better yet a deeper version of it - have some distinct advantages.
