Uhmmmm, I think asking for permission might be in order. A mean, his talking about excavation and probably that would be him altering the site and possibly,  the suspension of further dumping of dirt on that site.
Again, its a really serious one from what's his offering and I'm also supposing he doesn't have the resources to get the work going and would need the help of his city in funding the process too. A process that could be said to be a high stake probability of success looking back to the time this hard drive was dumped (8years+). So much for a rash action!