Nonetheless, they still have the potential to be an easier to implement disposal solution because they're faster/cheaper to create than a massive project.

I expect it'll still be necessary to put the hole somewhere there aren't hundreds of people protesting oil pipelines, but that's a topic for the future.

I heard of a place waaaaaay out in the woods - very few people lived in the area - near the Canadian Shield. One day some some Unidentifed People with serious machinery started drilling a hole. After several days, they went home for the weekend. When they came back, the hole had been filled in.

This re-occured a couple more times. The UP never returned.

Well, then. You need to dig it out and report what you find.