After a lot of thinking I decided that I really did not want to do #1 or #2 because I only have 4 acres of pasture right now and site #2 could be fenced in the future, plus #2 could only be about 175' long. I also wasn't crazy about having the ring basically adjoin the pasture because riding the older horse would probably send the younger horse into a tizzy. Far better to have some distance from the pasture and be closer to the barn! So I ended up picking site #3.
Site #3 was where the old cinderblock stallion barn was. It would have cost more to remodel it into something safe and useable than it did to have the Amish build a totally new, airier barn, so we demolished it to build the ring. Here's the barn being torn down (under the close supervision of a curious coonhound!):
You can sort of see in that photo that on the far side of the barn the land drops off towards the trees. (I wish I had taken some better "before" pictures.) The elevation difference between the far end and the near end was at least 10 feet (??), which is pretty substantial.
My amazing contractor, who is a horseman and engineer with tons of ring-building experience, took a long look at the site before we went ahead with it. Between the existing fence, the line to the sewer drain field, the property line, and the large grade we were cutting it really close. He needed to do everything very precisely to be able to fit in my standard dressage arena (66'x198') plus the swales needed for drainage. Thankfully he's really good at what he does. Here are some pics of the work in progress:
Below are some after pictures. I love it!!!!! The 3-board fence at the far end was definitely necessary with the huge drop-off (see below). I rode without it for a couple months and trying to really ride those far corners properly was a little unnerving, especially since my horse is so spooky. Now I feel quite secure.
Here are some photos that illustrate how much cutting and filling had to be done to make this site level (and why riding at the far end without a fence was a little unnerving!).
By the way, the cutting and filling did not cost me extra except for some topsoil and water that was trucked in (because we hit a dry spell during construction). As my contractor explained it, he has to strip the topsoil and move the dirt around no matter what to level and compact it, so the cutting and filling isn't that much more work.