> 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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