Planning to do some work to my outdoor this year and I'm looking at the GGT footing.
I have a 110 x 200 arena with manufactured limestone sand. I'm thinking of enlarging the ring to 130 x 200 and adding GGT. I've contacted them by email and am waiting to hear back but am curious to hear about experiences with adding this to existing sand footing and the costs associated.
Search the forums (I think Around the Farm, but am not 100%). There is someone on here who rehabs arenas and installs new ones, and I know I have read posts about them using that product. I think even about adding it.
My old BO looked into adding it to her arena (she has a coarse granite sand--which I don't think is ideal with GGT?). It was the maitenance and buying a different arena groomer (I think they recommended a Parma) that turned her off for now, more than the cost of the stuff if I recall correctly.
I love my GGT footing! I have a 150' x 200' arena that had about 8 yr old washed concrete sand in it when we bought the place. The rep came out and said the sand was good enough to use less of the GGT than was normally recommended, but it would still cost $7500. I ended up going with a little over 1/2 that which came to 4000lbs and spread it myself. It turned out very nice. I can always add more, but so far I'm happy with the amount I have. They recommend 10% moisture. I have sprinklers, so I water and drag before I ride. I found the used parma on craigslist and it works well with it.