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

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Subject: [TowerTalk] Digging a 5'x5'x7' hole in sandy soil - Followup
From: jeffhook@comcast.net
Date: Thu, 3 Oct 2013 03:41:18 +0000 (UTC)
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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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