Have you ever had a house that was inadvertantly built on a major drainage easement? 

Yes - I have dealt with garages, sheds, etc. that encroached onto neighboring properties or were built on utility easements but I have never encountered an ENTIRE house encroaching on an easement before.

Apparently the building permit did not show any restrictions so the builder went ahead with building this home over 10 years ago - despite the fact that the original plat (which the builder signed) shows this MAJOR drainage easement cutting diagonally through the lot. 

So - fast forward 10 years and the current seller is in a real dilemna because they were never notified about this nor was the first buyer who sold the house to them.  Looks like this will all fall back on the original builder and whether or not he is willing or able to vacate that easement now that the home has been built smack dab in the middle of this easement. 

By the way - this is not out in the middle of the country or obscure development but right in the middle of a very nice, upper-end golf course development southeast of Rapid City.

Unfortunately I had the buyer who has since had to pick a different house since it sounds like this issue may take weeks or months to iron out.