Theo, thanks for moving my post...
Here's a topo where I've drawn the property lines and approximate position of the pond. The pond is on a (relatively) flat area a couple hundred feet east of the stream that runs along the west of the property. It is elevated 10-20 feet above the stream bed.
Scott - The eroded bank isn't part of the pond, it is a second small stream running along the south property line. Those ledges looked worrisome to me, too. The stream doesn't feed the pond. There might be a spring, but I'd guess it was mostly from runoff. The current (long time) owner says the pond was there before his time, so has no idea how it was constructed.
I'm hoping to get back for another closer look this weekend.
Thanks for the input...
Keg