[TowerTalk] Tower foundation and bedrock

[Grant Saviers]

Hi Chuck,

An engineered spread footing can be used instead of a deep hole.  Some 
of the catalogs for big triangular towers show them.  Enough mass and 
moment resistance for a self supporting tower can be created several 
different ways other than the deep hole off the shelf design.

For DIY to the OTS tower base design, limestone should yield to a 
excavator hydraulic hammer or go down in the excavated hole with a large 
electric breaker (or an air driven jackhammer with trailer air 
compressor but they are a real handful).  One of the electrics wouldn't 
be so bad as the hole needed isn't much deeper than 3'.  Most rental 
yards have a Bosch, Hilti, Makita (what I have) or Dewalt on a cart.  I 
used a bull (spear) point in sandstone, hardpan, and shale, good to have 
a sharp spare. (plus eye and ear protection).

A small backhoe or mini-excavator (better, esp. for the conduit 
trenching) can be rented to remove the dirt and broken rock.  With 200 
acres maybe a nearby friendly neighbor's backhoe?

If the rock is granite not limestone, shale, or sandstone, that is a 
whole different ballgame.

Grant KZ1W

(Case '66/68)



On 4/7/2019 16:34 PM, Charles Lind wrote:
> I have the opportunity to put up a TX-455 tower on the property of my
> brother-in-law:  200+ acres and no zoning issues.  He says, however, that
> there is limestone bedrock about only three feet down.  Before I start
> Digging pilot holes, is there any advice a how to proceed with providing a
> solid foundation if this is the case.
> 
> Tnx, Chuck, N8CL
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