Thanks to all that replied.
I emailed US Tower and their Eng. (Remi) told me ..... " The foundations are
designed for soil class 5 per IBC2009 (table 1806.2). Your soil (sand)
corresponds to class 4, which has a better load capacity"
So I think I'm ok with the pier foundation. The pad foundation spec. for this
tower is 8'x8'x3' but the local city Eng. said I needed to be at least 54" down
because of frost hear in Minnesota, so it would need to be 8'x8'x54" in his
eyes.
I ended up watering the area for a few days and digging a 5'x5'x4' deep hole
and shoring up walls with four 4'x5' sheets of plywood and 2x4 kickers every
foot for support. I then dug the next three feet down and poured Portland/water
mix onto the sand walls. It soaked in and sealed in the moisture and seemed to
prevent caving. With the 2x10 top frame, I was now down 7' - 9". I assembled
rebar ca ge in the hole and had to wait 2 days for the cement truck to come. I
had ropes tied to all the 2x4 kickers and knocked them out as hole filled up. I
also rented a snake vibrater and I'm glad I did. It really helped filling in
the voids. I pulled the top forum boards today and recovered the footing with
plastic. In a couple weeks I'm going to dig down the sides and try to get at
least 2' of the 4' high plywood out. Ideally I should get it all out but Ill be
happy if theirs only a 2' band left in the hole. It took over a week and two
cases of beer to get to this point but it came out really nice.
I will be using a contractor if theirs ever a next time though. (this one beat
me up pretty good :o)
Jeff - KDØORH
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