Replacing liquefied clay with wood chip and pore water slurry.
I wasn't too clear about just when clays are at risk to liquify. It turns out probably many of the pro-glacial lake clays in Canada/northern-mainland-USA, are. If you accidentally drill to them, they might turn to mush and bubble out, and you are left with a sinkhole and a lack of structural integrity. But this could be useful if you could drill to some clay, and just pump out the newly liquefied clay slurry. I deally you could replace it with the wood chip and pore water slurry. Probably it would be economical to pipe the sphagnum fuscum pore water 100s of km. All the thick proglacial clay may then be suitable for a long-term carbon sequester.