Steve wrote:
Hi,

....
The main issue is that there is no way to avoid crossing the septic
system. Mine is about 45 years old.

I once heard you can't drive over any part of the septic system. What
he plans to do it to use ground protection mats to create a path to
the tree. He says it is not good to drive directly over the tanks,
but it would be fine to go over the pipes using these mats. In
particular this would be the pipe between the house and the tank (not
the leach fields). I estimate the pipe is buried only about a foot
and a half. He says that because of the round shape it can take a
great deal of pressure without breaking.

This is a site with mats like he is describing:
http://www.alturnamats.com/

Does this sound ok and safe to do or should I go the more expensive
route and get a climber?
.....

No problem as long as he doesn't put the truck _in_ the tank--the lids
are not designed to support that kind of load. I wouldn't worry too
much about the drain field for a (relatively) light truck, either, for
a field that has been in place that long as long as you don't do it
during a period of wet weather. That's not to recommend driving around
all over it, but a single track in and out during dry weather w/ a
truck that won't be more than say 5-6000 lb isn't likely to be a major
problem. If he were to start cutting obvious ruts in the area when he
started in, that would be a bad thing (TM) , but w/ the load
distribution mats I wouldn't worry much at all...