On Sat, 22 Dec 2007 15:03:21 -0600, Jon Elson
wrote:

Jim Stewart wrote:
I guess you don't have clay sewer pipes
under the yard. If you did, you'd have
had even a bigger problem.

I do, indeed! But, I know exactly where they are, and kept the
lift trucks well away from that area. I did manage to drive
over the vent riser of the soil line with a U-Haul truck when
moving in, and broke the top of the vertical pipe. I sweated
for a coule months that a big sinkhole was going to develop in
my back yard due to breaking the soil line, but I think I'm in
the clear as that was almost 20 years ago.

Not a problem - look in the Yellow Pages for "trench plate rentals"
in your area. They send out a flatbed with a knuckle-boom and a pile
of 1" thick steel plates with a threaded spud for a lifting eye in the
center. They can back up and drop you a nice "instant road" through
the backyard as they go, leave them for a few days as you do your
moving project, then come back and pick them up.

Probably cheaper to call them than to buy an equivalent pallet-load
of 3/4 plywood that you'll destroy doing the job, even if you put it
down triple-layered. Then you have to pay "rent a bin" for a small
roll-off to dispose of all the splintered plywood. And the rental
company for the flat tire on the forklift when it broke through...

-- Bruce --