PG&E announces plan to bury thousands of miles of lines

[melm00se]

21. I'll add to this

with this quote

“The estimated cost for constructing underground transmission lines ranges from 4 to 14 times more expensive than overhead lines of the same voltage and same distance. A typical new 69 kV overhead single-circuit transmission line costs approximately $285,000 per mile as opposed to $1.5 million per mile for a new 69 kV underground line (without the terminals). A new 138 kV overhead line costs approximately $390,000 per mile as opposed to $2 million per mile for underground (without the terminals).”

Source

Bear in mind that these numbers are more than a decade old so the costs (in materials if nothing else) are going to be a significant percentage higher than in this study.