I am in-process of installing a LM470. This is the first time I've
installed a self supporting tower (with this size footing) other than a
telephone pole and that was done 40 years ago at a totally different QTH.
I got the hole dug per Tri-Ex specs of 3.5' X 3.5' square but I went 8' deep
to add a little safety margin because the Tri-Ex drawing doesn't really
specify the soil type that the drawing is based on. I also extended the
rebar 1' in the tower base to go to within 4" of the hole bottom (as Tri-Ex
shows). My soil is basically hard clay with pockets of sand as I dug
deeper. As I got below 6' deep, I noticed water seepage into the hole from
two small fissures, one each on two opposite sides of the hole. The
fissures are light gray in color as compared to the soil which is a reddish
brown. The seepage rate is approximately 1'/24 hours in the 3.5'/3.5' cross
section or approx. 3.8 gal/hour.
I have a swimming pool 10' away from the hole, but the pool water level
doesn't seem to be dropping any more rapidly than it ever did (due to
evaporation). However, I doubt I'd notice 92 gallons loss in the pool over a
24 hour period! I also live on the side of a hill where I wouldn't expect
to see too much ground water captured in the soil. Yet, we are far from the
top of the hill. I asked a surveyor friend (not a geologist) and he
claimed that the water collection in this type of soil is not uncommon. The
fissures are not on the side of the hole towards the pool.
I am ready to install the rebar base into the hole and pour the mud. Should
I be concerned about this seepage? Has anyone experienced this in their
installation?
73, Mike-K6QD
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