I am in the process of constructing a 3 acre Farm pond in Upstate NY. My excavator favors Corrugated Steel culvert tubes for the overflow but I think using Plastic culvert tubes would would be the better way considering the Plastic will not rust and last much longer. I will install a venturi riser tube to draw off the water from lower depths. The downriser/horizontal discharge tube will be 2' diameter and the venturi oversleeve tube will be minimal 3' diameter. Using the formula Area = Pi x R(square) I deterimined that a 3' oversleeve will be needed to feed the 2' downriser. If I use the plastic culvert material I would use double wall (smooth on inside and ribbed on outside). Is 3' diameter plastic culvert an available size? If not what next size up is available? Are Anti-seep collars available to mount on the 2' plastic double wall culvert? Are 2' ells available as well ? Will plastic culvert material in this size stand up to racking stresses of 3 foot thick ice ?