I don't think the water is an issue for the foundation, but I can say
from personal experience it sure can be a headache with respect to
INSPECTION if that's needed prior to the pour.
Inspection was required at my site and the inspectors wanted to see no
more than 1/2 inch of standing water. And the rebar had to be in
position when the guy came to inspect which was another headache. I
could not drop the cages into the holes because repeated rains would
cause slight sidewall erosion and the nice initially square holes would
round-out taking on a bowl shape. Hired two high school guys to square
out the holes when it looked like things were drying up a bit, of course
each time the hole got a bit bigger.
There were 12 holes we wanted to pour and it took 3 months of waiting to
find a time window where most of the holes were dry. I think there were
3 of them that had to be pumped and one was at a point in the yard where
it would fill up in a couple of hours. For that one I sunk a 5-gallon
bucket into the bottom of the hole so the top was flush with the hole
floor. That would let the sump pump fit down through the rebar and into
the bucket where it would keep the hole drained. I ran the generator
and pump until the inspector showed up. Pulled the pump. He looked at
the hole and signed it off.
Poured the 12 holes all in one day. Each guy anchor ended up taking
about a yard more concrete than Rohn spec - that increase from all the
sidewall cleanup by the boys over the summer. For sure those things are
never going to fly out of the ground, no matter how big the tornado is
that comes calling...
If the county would have let me poor the holes with water in them, I
could have had the project done months earlier!
So my guess is that the water is not a issue with respect to the tower
base, but it is going to provide some challenges in other areas. Good luck!
73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com
On 5/28/20 12:36 AM, Mickey Baker wrote:
Hi Don, and all,
I live in Florida and once had a bridge and connecting seawall adjacent to
my property replaced.The new seawall connected to mine, so I watched the
pour right next to my dock with interest.
They brought in an excavator, dropped sheet steep forms on the water side
of the new seawall and used the excavator and removed the old seawall and
several yards of muck. Water never drained - they built a plywood form into
the water on the land side of the seawall and steel sheets on the water
side, all the way up to a piling on the bridge. A long steel rebar cage
with a coating (zinc chromate? Yellow) was placed into the trough.
The pour was supervised directly by the project engineer. He examined
everly load with a slurry test and the chute from 3 trucks full of
readymix was poured into a placement box, a 12" plywood square tube about
6' long reinforced with steel straps every foot or so. It fit perfectly
between the rebar. A worker stood on the form and filled the tube so that
it placed the concrete into the bottom of the pour without mixing with sea
water and picked it up and moved down the rebar squares, got to the end and
started back. There were four courses, so it appears they placed 2 feet per
vertical course. The final course was above water and was poured directly
and finished.
So concrete is placed directly into water - into sea water even - and lasts
for decades.
As everyone has said, find yourself a good engineer who knows how to design
and pour footings in your local geology. It will be good money spent!
Mickey Baker, N4MB
Palm Beach Gardens, FL
*“The servant-leader is servant first… It begins with the natural feeling
that one wants to serve, to serve first. Then conscious choice brings one
to aspire to lead." Robert K. Greenleaf*
On Wed, May 27, 2020 at 6:44 PM Don Solberg <dsolberg8132@gmail.com> wrote:
I was planning on purchasing a used US Tower HDX-572, 72 ft crank up
tower. It looks like I may have run into a problem with the foundation. I
had some trenching done today for a new well and discovered that the ground
water level is just slightly lower than 6ft. US Tower specifications call
from a 7.5 foot deep hole. My soil is mostly sand, so in addition to not
being able to go down 7.5 ft, I probably also want to make the foundation
wider.
Is it practical to put up the 72ft tower with a wider pad, or should I look
at getting a smaller 55ft tower? Another alternative is find another
location for the tower. I have about a 10 ft hill on another property that
I own across a gravel road. This would most likely eliminate the ground
water problem but I would have about a 300 ft cable run and I would have to
trench across the town's gravel road.
I am looking for recommendations.
73,
Don K9AQ
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