Thanks Steve -
The engineer didn't want to do a formal analysis, and there is no permit
involved. Undisturbed soil is what I'd heard, but the HyGain book doesn't
mention it. I have no idea how old it is.
Still in Duval, so care is certainly advised. What that means in terms of real
life shovel-in-the-ground practice, I'm unsure.
73, Mike
On May 1, 2014, at 11:31 AM, K7LXC@aol.com wrote:
> > I'm negotiating to get the base for my HG70-HD dug and poured. I have a
> > high water table, soil tends toward sandy, and an engineer said he would be
> > happier if the hole were 10' deep rather than the 7.5' called for in the
> > manual.
>
> > The concrete guys I'm talking to want to line the hole with plywood to
> > prevent collapse. One guy who does a lot of big sign installations says he
> > does it regularly, and there would be no stability issues.
>
> > I've read several times the pour needs to be into undisturbed soil, no
> > backfill, altho that's not in the manual.
>
> > What are the facts?
>
> Howdy --
>
> First, your engineer should be specifying everything - including hole
> depth. What does it say on your building permit plans? If in doubt - I'd go
> for making the engineer happy and overbuild it.
>
> All the tower specs I've seen call for the base to be poured into
> undisturbed earth. If you do have to use forms, you'll have to be very
> careful with the backfilling. Put some in, tamp it down (a Jumping Jack is
> the way to go), and repeat.
>
> If you're still in Duval County, it's a 95 MPH windspeed zone so I'd be
> real careful with all aspects of the installation. And pretty conservative
> with everything.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
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