Hi, Jim, and all,
My QTH is surrounded by water - I'm on an island about 350' wide made
mostly of dredged muck.
To keep the tower base hole dry here in my Florida QTH, I used a relatively
small pump (50GPH @ 8' lift) and a perforated PVC well screen to keep
standing water out of my hole during the period between dig, inspection and
pour. I also built a 4 sided caisson with removable cross supports and
handles to keep "undisturbed earth" undisturbed. Luckily no rain or
erosion, we kept the hole dry and easily removed the plywood and positioned
the steel a few hours before the pour. 4' x 4' x8' deep hole, conveniently.
Tidal intrusion was the only water we needed to worry about, but it was
minimal at high tide and the pump handled it.
I had a tarp covering the hole and a small berm around it to ensure no rain
entered.
Everything evidenly worked well. The critical data is that your pump(s)
must pump faster than water intrusion and you must be mindful of erosion.
And, of course, the footer you're pouring should be designed appropriately
for your situation.
73,
Mickey N4MB
On Sat, Jan 11, 2014 at 10:54 PM, Jim Lux <jimlux@earthlink.net> wrote:
> On 1/11/14 6:53 PM, Mark Robinson wrote:
>
>> A ham in Florida (which has a high water table) just had a big hole dug
>> for his tower. The company used what is called a well point. It is
>> defined here
>>
>> http://dictionary.reference.com/browse/well-point
>>
>>
>>
> Another strategy used on large excavations is to pump liquid nitrogen into
> the soil and create a frozen barrier to water infiltration.
>
>
>
>
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