[TowerTalk] Digging a 5'x5'x7' hole in sandy soil - Followup

[jeffhook at comcast.net]

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