About where I think the N loop becomes the S loop. Right before the wooden bridge / feature that is right before the carpet trail entrance. You can see the water and the kayak rentals.

Pretty sure it will require a chainsaw. Had a bit of trouble climbing over it, lol.

I always let the guys at the bike barn know about stuff like this before I leave the park.

If you find a tree down please stop by the Trail Center before you leave and discuss it's location with a Staff member.  They can help to pinpoint it on the map so I can locate it easily with a chainsaw.   
As much as I'd like to, I don't get to ride the trails all the time to find these things myself, and trying to decipher someone's internet description usually just leads to lots of hiking around carrying chainsaw gear (not the most enjoyable thing in the summer).   
I'm not always able to get to every tree right away, but the sooner I have a good location the quicker I'll be able to make time for it, and the better info I have on the location, the easier it is to make time, because I know I won't be wandering around in the woods searching aimlessly.