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.

Jon