We're building on lakefront property in Mississippi that has a slope of at least 25% grade. The grade does decrease to about a 5% grade at the back of the house. The foundation is 8x8 with spans of ~10ft and the 8x8 heights vary from 4 to 16 ft. The 8x8s rest on 3 ft deep concrete footings. Our concern is water pooling around the post (due to possible erosion) and the stability/strength of the foundation. Any ideas out there as to the valibity of our concerns, whether they're well founded (no pun intended) or not?

The bottoms of the posts should be at least 6 inches above the highest point of the ground adjacent to it, and should be connected to the pier/footings with a metal post base. There are several types available, but for 8x8's you may have to have them fabricated.

So any ponding that may occur will occur against the concrete, not the wood.

The biggest concern on such steep slopes is that the footings themselves may slide outward and downward. They should be big enough that the area of their downslope face will not produce soil loadings greater than the soil is capable of resisting. This will require some soil testing and calculations by either an architect who knows what he or she is doing, or a structural or civil engineer.

Another method of dealing with this possibility is to tie the outermost footings back to the footings next up the slope.

Without a lot more information (footing size, soil characteristics, exact grades, etc.) it is not possible to comment further.