Brandi, TSC has 15" dia. x 20' long plastic culverts for $199 each. I don't know that one culvert would be enough in a heavy rain, but don't want to go to 24 because the culvert would need to be buried 11" deeper. I'm thinking two 15" culverts side-by-side with 18" of clay between them for a good seal. That will give me the flow I need and allow plenty of freeboard up to the dam level. One of my problems is that I sold my 18' utility trailer and only have my 12' dump trailer. I'll probably have to have the culverts delivered. I'm going to check with a couple of local lumber yards too. If I can buy local for nearly the price of TSC and give a local business my money, I'll do that, even if it's a few more dollars. One little lumber yard offers free delivery.:thumbsup: