J.R.,
If your LWA concludes you have a degraded wetland that you want to mitigate, you can probably file under the Nationwide Permit number 27 for wetland restoration activities. Under this NW permit, there are not linear or acreage limits (such as the 1/10 acre your friend mentioned - probably referring to NW permit 18 or 39). Remember, you will have to restore these wetlands on-site, not replace them all together with the pond alone.
I don't mean to rain on your parade, but as for asking forgiveness...you'll have to do that before a federal judge should anyone decide to report you or stumble upon your project. Violation of these wetland laws is a federal offense punishable by federal pen time and/or excruciating fines.
We recently had a client that tried to go the route of "dig and ask permission later". They were reported and given a cease and desist order from a federal judge. Then, they had to go before the federal judge and try to plead "ignorance". At the end of the judicial process, they were slapped with a $1M+ fine for violating these laws. I don't wish that on anyone.
Before you close on the land you're looking at, resolve to follow through with your project the legal way so you don't pay for the consequences later. It's much cheaper to do something right the first time, than try to fix what you shortcut, after the fact. It's the responsible and right thing to do. Otherwise, find another piece of land that you can build a pond outside of those jurisdictional waters.
Here's your professional advice, at no charge.
