Finally a homeowner again, but need some legal advice

I think this is not a simple one.  You've got to give owner plenty of notices, estimate the property value, then charge them XX number of days until the value becomes zero.  Then one last notice of disposal and all charges associated with it (rent space, disposal, labor/administration fee, etc).  After that, you have to worry about content.  When everything all lined up, I would try to get a court to approve of disposal so nothing comes back to you.  Send a copy of the court result and you're good to go.

Or, you can ask them whether you can dispose it and get their approval in writing to do so.

On either case, I am afraid you have to eat the cost of disposal.

Then again, I may be overthinking this ... 

Good luck and big congrats on the house for generations to come!