So if you start on a piece of land you largely control, or can quickly get permits for, you could theoretically bore until where you need the next permit. It's

So if you start on a piece of land you largely control, or can quickly get permits for, you could theoretically bore until where you need the next permit. It's not quite that simple - you may largely control the land you're tunneling under/through, but when you remove a large amount of soil, the surround ground may shift or you can affect water tables and those can cause issues for adjacent parcels and structures. Spoil removal (meaning muck trains and/or dump trucks to haul away dirt) will also affect adjacent properties through dust and noise. Unless he owns hundreds of acres of property, any tunneling activity will cause issues that will come up through the permitting process. And if he does down hundreds of acres of property, why not just build a surface road?