It's built with concrete and bricks. Nothing fancy, just a floor and then the wall, thick and strong enough to hold quite a bit of water, with pipes for pumping water into and drain out of. This one had some cracks in the wall that we thought were o.k. until we filled it one day and ended up with pieces of dam wall flung yards away. Miraculously no-one got hurt, but we had a VERY wet yard afterwards. We didn't bother fixing it and turned it into emergency pig housing later. There's a pic of pig in residence in this thread: https://www.sufficientself.com/threads/what-do-you-do.14038/
That could be an option. There is a dairy farm not too far away and i have seen several bottle calves around there. I not sure if i could butched a calf in the back yard though. Seems smaller would be easier to process myself