Cecil
If you have pictures available of your emergency overflow can you post them here or if they are elsewhere on here post a link to them. My thought is if I had the oportunity to pull water out the bottom it would also pull out sediment that would be on the bottom. My concern is to not have a problem down the road with it. Dep recommended a drain but would not recommend a type. The average rainfall map I got from DEP is putting my area at 35-40 inches a year on average so I am definitly going to need a spillway also. Here is the link if anyone else is from PA and looking for rainfall amounts: http://www.erh.noaa.gov/ctp/hydro/normalprecip.php

Dreaming of the pond!