[Xabia Jim]

If it's really "all clay" down below, your water is running on the top of the clay. Clay does not give up water that fast unless it has sand stringers in it. A pure clay is quite "tight". How thick was the clay (how deep could you go?)

Bail out the hole a few times and see how fast it recharges. It could just be local drainage from the sand/gravel interface on top of the clay layer.

If you have slope to the property, you could put in some draingage pipe and let gravity do the work.

do you know any friendly builders in the area...you could find out what types of foundations are put it there.

Jim