Expansive Soil, Clear Lake City, Houston - How deep? (credit, design)

[mdh1]

Hi,


Does anyone happen to know how deep the expansive clay is in Clear Lake City or anywhere near here?
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[SIZE=3]Here is the situation... [/SIZE]
I've had a couple foundation repair companies come out and inspect my foundation (slab on grade with post tension design) after noticing some settling. Some companies use pilings and others use bell bottom piers. The piling companies said that piers won’t work in this area because the refusal on pilings in that area are at times up to 30’ and piers will only be about 12’ - 15’ deep. When I asked the pier companies about this they said the piers only need go deeper than the soil with seasonal moisture change and 12’ – 15’ would be fine. Although the engineering behind piers make more sense to me than pilings, I am not sure if the engineering holds if it not deeper than all the expansive soil. If it doesn’t, I might have to go with pilings even though the engineering of it is not my preferred method.

All these companies just promote their method and attempt to discredit everyone else's way of doing it which makes it very hard to choose. (BTW, I really hate this approach to salesmanship . It seems to be consistent with many companies doing this work)

I think I really need to understand the condition of the soil to make an educated decision on method. Does anyone know how deep that expansive clay is in Clear Lake City and can anyone comment on the depth of a pier relative to the soil with seasonal moisture?

Thanks!