[TowerTalk] towers in dirt

Tue Mar 29 00:47:42 PDT 2011

On 3/28/2011 11:47 PM, Mike Ryan wrote:
> How do the legs of the tower drain while in dirt?  Depending on whether you
> are in state that gets 'frosty' or not can also be a clue to the short life
> of a tower due to the dirt it's planted in. No way I would even consider
> that kinda' project. Unless...I could convince my mother-in-law to climb it
> that is. - Mike
This is what I do, I am not advocating others do it unless they decide 
that is what they want to do. That is their decision.
I'm in Michigan where the ground is frozen solid for about 4 months out 
of the year and two more months where there are lots of freeze and thaw 
cycles.  Freezing tower legs due to poor drainage has never been a problem.

First, this is a "Guyed tower" we are talking about, not one that needs 
a lot of concrete to stay upright. Remember all the concrete does is 
serve as a large enough plug to keep the tower from sinking or the base 
moving sideways.
For dirt bases I now make my own. they consist of 1" or 1 1/4" solid rod 
for the legs with 1/8" steel plate for the side plates.

Drainage. Depending on the base (I use bases with solid legs)The tower 
legs have about a 1" clearance between the bottom tower leg and the top 
of the base legs.  The only towers I've seen with freezing problems were 
from cobwebs in the legs serving as dams to stop moisture. That froze 
and then more water collected on top of it. The other freezings were 
from improper drainage of the base legs.  I'd also seen legs rust off 
right at the top of the concrete due to poor drainage or no crown on the 
concrete.

There is no real secret to long tower life in dirt unless you count 
keeping air away from the moisture and dirt interface.

BTW the sol around here is quite acetic.

Nor do you need soil tests or an engineering degree to know whether the 
soil is adequate or not.   Normally after the soil has settled you can 
not move the base, or even pull it out of the ground using an 4 ton 
engine hoist.  IF you can move the base at all after two or three weeks 
the soil is not adequate.  I install the base plus one or two tower 
sections, plumb it and let it set for a couple weeks, then check it.

For hollow base legs, (remember we used to set the tower base in 
concrete rather than using pier pin base)
The legs must reach into a gravel or crushed rock base. by several 
inches with dirt "on top" of that.  ROHN even used to make a dirt base 
for the 20 and 25G.  If hollow those base legs *must* drain into crushed 
rock just as if it were a concrete base.

In over 50 years of using dirt bases on "small" towers I've never had 
one fail, nor have I ever had tower legs freeze, or rust. I have seen 
poorly installed bases go to pieces because the ham though the light 
soil or sand would provide enough drainage.

Climbing?  I do not advocate any one climbing any tower where they are 
uncomfortable climbing.  I have taking towers with improperly installed 
bases where the legs had rusted.  I cut them off, set them on the ground 
and set them in by several inches. With adequate guys the tower was a 
solid as one set in concrete.  I've climbed 90 footers set in dirt that 
felt every bit as solid as those set in concrete.  I've also tested a 
few set in concrete and refused to climb them with the suggestion that 
they just cut the legs and guys and dump it over.  I climbed one that 
was set in concrete, bracketed to a house, and guyed that almost got me. 
One of the base legs was rusted through, but was not apparent in the 
inspection.  No problem, it's guyed and in concrete AND guyed anyway? 
Well... while I was up thee at the top of the *3 story* house, I turned 
around and felt the tower move. I grabbed behind me and by luck caught 
the bracket with my left hand. It seems that the bracket at the top of 
the house had broken as well.  After getting two hams to hold the tower 
in place against the house I climbed down and we just tipped it over 
into the snow.

I am far more concerned about water trapped in tower legs due to spiders 
or other critters.  I once took a tower apart and dumped about a quart 
of corn kernels out of each leg.  There were several splits from 
freezing in that one and one of them was within 2' of the top.

My 45G sets in several yards of concrete and each guy anchor weights 
over 17,000#.

I would put neither that much weight or that much wind load on a 25G 
even with a concrete base.

> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Cqtestk4xs at aol.com
> Sent: Monday, March 28, 2011 10:55 PM
> To: TOWERTALK at contesting.com
> Subject: [TowerTalk] towers in dirt
>
>
> In a message dated 3/29/2011 2:25:10 AM Greenwich Standard Time,
> k8ri-on-towertalk at tm.net writes:
>
> For up  to a 50 or 60' 25 G I just use dirt and a dirt base.  It's a
> guyed  tower and all the base does it keep it from sinking or sliding
> sideways.
>
> NOTE: not all soil is suitable for a "ground  base"
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> That is a scary thought.  Who determines what is "suitable"  and how is it
> determined by the layman.  Compaction tests? Engineers? How  acidic is the
> soil? etc., etc, etc.?  It sounds a lot easier and safer  to dump ready mix
> down the hole and do it right.  5 yds of ready  mix (3000 lb) runs $80/yd
> down here.
>
> I've seen guys put a tower in dirt and a few years later it looks  like
> something I wouldn't climb.  Leave a tower section laying on dirt a  couple
> of
> years in an average moisture location and you'll  see what I mean.  That's
> why guys raise them off the ground when storing  them.
>
> Bill K4XS/KH7XS
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