Thank you everyone for so much help! Here are answers to some of your
questions:

1) The backyard will be foot traffic only. No cars or even ride on
lawnmowers.

2) The pipes are all copper. 2 x 1" steam pipe. 2 x 1/2" hot and cold
water. 1 x 1/2" natural gas pipe.* 1 x 1" natural gas pipe.*

* = The 1" natural gas pipe feeds the boiler/water heater and goes from
house to garage and is barely 12" below grade. Is this safe? Secondly,
the 1/2" gas pipe feeds the dryer and is flexible copper and is just
kind of laying in the hole, with no support. The flexible pipe is bent
and bowed, and was only 6 inches below grade at points. Any
suggestions?

3) The water and steam pipes are all adjacent, while that gas lines
average about 1 foot above them, and are separate from the water and
each other. Should hot and cold water be insulated together?

4) Thanks again!