Actually, it appears I need to put two strands of electric wire about 4 and 8", or 6 and 12", from the ground.
I took some temps in the pen tonight. It's still 92F out (gack!!) and the earth covering the burrow is 112F-114F, but inside the burrow it is a cool 84F!! I wonder if I should put another 1000 pounds of dirt on it. It's not expensive, and not really that much work.
I didn't do any more work on it today, but bought drip irrigation supplies. I'm going to run the feeder hose around the inside perimeter of the pen (it's practically already dug up!) and then run the 1/4" tubing to whatever I plant. Drip irrigation makes keeping anything you plant alive so simple by making daily watering effortless. I just need to bury 80 feet of hose from the well to the pen.
Nanci