well i love overflow pipes they are the best thing to happen to most ponds. i'm not familiar with your dirt but here in osage county oklahoma i have never put a pipe in a pond for the nrcs with less than 20 acres of runoff and i say never except once it shed 15acres and was spring fed. the nrcs was afraid that it would keep spillway soft and cause erosion.they are very particular not to disturb the grass on spillway during construction of these ponds. i havent had any problem with these ponds but we did spend a lot of time picking the sites. we looked for good vegetation growing on spillway area if you dont have that i would recommend a pipe it shouldnt take a very big one thou. the 15 acre one has a 6" pipe no riser just a hood cut on end of pipe with 2 anti-seep collars the pond has 3' of freeboard is 5 years old with no sign of erosion on spillway. one other thing we had in our favor was that these were all for big ranches so we had a lot of area to pick our sites from. so if ur worried about it you should be able to get 70' of 6" pipe for around $400 and get it welded up with anti-seep collars for another 4 or 500 bucks i would think. just bought 140' of new 6" for a bottom drain of a big pond for 6.90 per ft. just given you some examples hope it helps and all these ponds had 10' wide spillways with 2' of freeboard

Last edited by tim pinney; 05/10/10 11:44 PM.