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Re: [TowerTalk] Soil Composition and Tower Bases

To: "towertalk" <>
Subject: Re: [TowerTalk] Soil Composition and Tower Bases
From: "Al Williams" <>
Date: Mon, 31 Jan 2005 11:34:37 -0800
List-post: <>
> > I have checked in the documentation for the crank up towers that I
> > have
> > and I don't see any information on the soil composition factoring
> > the tower base dimensions. The base is spec'd to be 3 x 3 x 7. Does
> > the
> > soil composition enter into this picture at all?  The tower is a 70'
> > unguyed crank up.
> >
> > The hole will be underdisturbed except for the hole specifically.
> > Logic

My experience follows:

The stress analysis for my LM470 (70' motorized crankup), when following
the footnotes, sentences, etc. indicated that the analysis applied to an
installation to be in "massive, crystalline granite"!  This,
plus that the windloading parts of the analysis referring to wind speed
had 70 (mph) crossed out and 80 (mph) penciled in-- along with a
corresponding decrease of antenna square feet allowable.  This held up
my building permit for a whole month while the county engineer and the
PE came to an understanding which I think was that was the "massive,
crystalline granite" was meant to imply that
the user would have to provide a soil foundation analysis.

The stress analysis for my HDX572 (72' motorized crankup) flatly states
that it is up to the user to determine the required soil foundation

Although it doesn't provide a technical solution to your concern,
consider this:
The total cost my LM470 installation including cost of the tower, tower
transportation, digging the hole, pouring the concrete, mast, rotator,
cabling, ground rods and wire, lightning protection, antennas made the
cost of an extra yard or two of concrete insignificant so I went from a
3x3x7 to
a 4x4x8 fill.



See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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