Bob, KB8TL wrote:
"Anyone have any thoughts on why this might not work?"

I`ve worked in several medium wave broadcast stations which used buried
coax to feed the towers. No problems..

I worked in a shortwave broadcast plant where we needed a 100 KW dummy
load. So we constructed a parallel wire 600-ohm line only about 2 feet
above the earth using Copperweld wires a few hundred feet long. It could
boil the dew on the groud and bring earth worms to the surface. It also
did a great job of dissipating the 100 KW.

Anytime parallel line such as twinlead or ladderline approaches ordinary
earth, loss soars. Direct burial is impractical even inside fairly large
conduit. Use one or two lengths of waterproof coax as buried line.

Best regards, Richard Harrison, KB5WZI