DO NOT DIG post holes near that gas line. In fact, since you likely aren't sure EXACTLY where the gas line is, have the gas company (and if there is any buried power the electric company) come and make sure there is nothing where you want to dig post holes.
The law in Vermont (and I presume it is common in most states) says gas and power lines need to be 18" down so you don't need to worry about the chickens digging into them.
There are deep tap roots under the trunk and lots of feeder roots that spread out higher. You will find feeder roots all the way out to the drip line (widest part of the canopy). Watering a large tree at the base is a waste. Nature waters them at the drip line, which is why the feeder roots are there.
The law in Vermont (and I presume it is common in most states) says gas and power lines need to be 18" down so you don't need to worry about the chickens digging into them.
There are deep tap roots under the trunk and lots of feeder roots that spread out higher. You will find feeder roots all the way out to the drip line (widest part of the canopy). Watering a large tree at the base is a waste. Nature waters them at the drip line, which is why the feeder roots are there.