Topband: Radials over a stone wall

[Bill Wichers]

The directional drilling rigs used for fiber installation "under
highways", etc., aren't *attachments*, they are big hydraulic machines
with 6 figure price tags. I doubt very much anyone would lone one out,
and I wouldn't want to borrow one if I didn't know how to run it. Also,
directional drilling is generally most economical for runs under
pavement and the like over relatively long distances (hundreds of feet
or more) where it saves the significant cost of cutting pavement and
repairing the cut after trenching. If you only want to go under a wall,
the setup/teardown time for the crew will likely make the per-foot cost
ridiculously high. I contract this kind of project at work frequently
and my minimum cost is about $2,000 per shot due to setup/teardown costs
for short runs. For longer runs (1,000+ feet), the cost works out to
around $6-10/foot depending on the project and grounds restoration
requirements. Also, the directional drilling rigs have minimum distances
they can work in since the "down and back up" curve is limited by the
flexibility of the drill rod (which is basically steel pipe).

Most of the CATV drops to houses are "plowed" in, which is done by a
machine similar in size to a riding lawnmower but with a vibratory plow
attachment. This is quick and cuts a small slit in the ground while
pulling the cable behind the plow. You *can* go through some pavement
(like asphalt) with these rigs but they can't go through walls.

There *is* a poor-man's method that might work here: you can dig a hole
on either side of the wall below the bottom of the wall. You can then
use a small pipe with water running through it (such as from a garden
hose) and then use that to "bore by hand" under the wall. If the ground
isn't too rocky this method can work pretty well, although it's really
tedious if you need to do a lot of bores.

  -Bill

> Tony, no need to fret about drilling. I would say than going under is
> better than going over.  The crews who do direct burial for cable TV
and
> fiber have special directional drill attachments that you should try
to
> borrow. the will go straight down along the wall until they get to the
> dirt under the wall, find their way under the wall and come up on the
> other side.  You just a need a few of these connector and for them it
is
> something they do all the time under highways, concrete drainage and
> sidewalks, as a matter of their work.
[snip]