Rick Karlquist wrote:
> Rudy Bakalov wrote:
>>> My property has a very high water table and as a result my builder and I
>> decided to build the tower foundation mostly above ground. Specifically,
>> we dug a hole, filled it with compacted gravel that is above the water
>> table, covered the gravel with very thick sheets of plastic, and inserted
>> 2' styrofoam boards around the base. Then we poured the concrete. As a
>> result, only about 1.5' of the foundation is below ground, 3.5' are above.
>> The overall dimensions are 10' x 10' x 5'.
> All the books I have read say that in cold climates, foundations
> must go below the frost line, or there will be "heaving". You
> are clearly in violation of this dictum. Your only hope is to
> prevent any freezing near the tower. Seems difficult in Ontario.
> You could also try installing a "sump pump" to drain away water.
> This has to run semi-continuously because water will seep in
> to equalize the water table.
> BTW, I hear that in Florida, they install towers foundations below
> the high water table all the time.
When my aunt and uncle installed an inground swimming pool at their
house in New Orleans (below the level of Lake Ponchartrain) they
basically had to build the pool in water. The water comes in so fast
you can't pump it out quick enough to keep an excavation dry, and you
have to fill the pool quickly to keep it from floating up out of the
soil. I don't recall all the details from 30+ years ago.
These days, I understand that they use liquid nitrogen injected around
the excavation to freeze the ground water. Seems like it would be
expensive, but probably not as expensive as underwater construction.
In any case, there should be ways (not cheap) to build an antenna
foundation in a high water table.
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