[TowerTalk] Solutions for Tower Base in Fresh Water?

[Larry Libsch]

Group -

         Our club has bought a tower for use at our new club shack on 
the edge of the 'glades. The 'glades is fresh water this far north and 
west. The water table at the site is 30 inches below ground level. The 
soil is mixed gravel, sand, and earth fill for about 2 1/2 feet, then 
wet sand below 30 inches.  Our tower is an old Rohn  with a three legged 
tilt base to which the tower attaches. The Rohn plans for a concrete 
tower base suggest the bottom of the 6 foot, open, galvanized steel legs 
of the tilt base be placed into 9 in of (dry) sand and the concrete base 
poured around the legs above the sand. It seems likely that the the tilt 
base legs below the concrete base will always be in water, and that 
water will stand inside the legs to the level of the water table. Much 
of the concrete base will stand in wet sand below the water table.  As 
concrete is water permeable and drys slowly, it is likely that the 
outside of the tower base legs will also be wet from the top of the 
concrete base down.  We seek an understanding of the special problems 
this situation presents to the safe construction of a tower base and 
solutions to those problems. So far, we recognize three likely problems:

         1)   Corrosion issues with the steel legs both inside and below 
the concrete base. What can we do to minimize this problem?

         2)   It seems likely wet sand is a less firm base than dry 
soil. What changes should we make to the size and /or the shape of the 
concrete base from the Rohn plans?

         3)   Any hole deeper than 30 inches fills quickly with water. 
Will we be able to dig a hole 7 feet deep and 5 feet by 5 feet wide? If 
we manage to dig an acceptable hole, it will fill with water.
          Can we pour concrete into a water filled hole and have it set 
up properly?

                                                                         
                                                                         
     Larry,  K4KGG