Patrick,
There is another issue you must contend with- drainage of water and
condensate from the tower legs of any tubular tower. I am a tower monkey in the
DFW area and I cannot begin to tell you how many freeze splits I have seen in
the tower legs because of inadequate drainage. I removed one Rohn 25 tower that
was very similar to what you have proposed. The tower base was dug down about 2
1/2 feet until the caliche was hit. The tower legs rested on the caliche rather
than a bed of gravel and the concrete was poured. The freeze split on one tower
leg was 4 1/2 feet above ground, far above the normal 1 foot I see in the area.
Rohn specifies a gravel bed for drainage for this very reason. By only digging
down until you hit the caliche, you are compromising the mass of the base and
if you put in the gravel, even more so. The caliche can be dug out with effort,
something you will need to do for the guy posts anyway. A hammerdrill can be
used to to start a hole and once you have an
area to break off the caliche into, it will break. One step up the tool
ladder is a demolition hammer. The bottom line is don't cut corners on the
installation. Follow the manufacturer's specs. They are there for a reason. If
you can't make it work, don't guess, get a engineer involved. BTW, do you have
overhead powerlines or a drop nearby? My personal safety factor is 2 times the
height of the tower to the nearest line.
73 es gl,
Jim W5QM
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|