The amount of garbage out there is probably unimaginable. We're not just talking about small debris, but very large debris, like the size of vehicles or more. I'm not sure how you would lift it all. Even smaller stuff, like small tank size, would not be something I think you could probably be able to get except by using some kind of crane. It would probably take many, many billions of dollars and hundreds of ships to make a dent. (Not just tsunami debris, there was a lot of debris out there already and always increasing.) You would need to transport it all once a ship got full and then find someplace to actually put it all. (Maybe some things could be recycled, but being at sea so long I'm not sure how feasible it would be.) And some things would be dangerous to handle, with fuel left and maybe even some material from the tsunami that could come from areas that we're radioactive. (although I would imagine radiation would not be too much of a concern except the land and items still near to the leaking plant)

I just don't see anyone stepping up to pay for it. It's such a large area we are talking about and so much garbage. I'm not even sure they could pick it up fast enough. You would probably need to build specialized ships, with cranes, that from now on had the job of picking up the debris. I'm not sure how you would skim for smaller debris unless cranes picked up the big stuff and then you came over the area with specialized nets, which would probably be incredibly more difficult than it sounds. And then again, imagine the area we are talking about.

I would not be surprised if it cost trillions and that humans might not be able to pick it up fast enough than more is added. Eventually some of it may sink more and more along with some of it breaking down. It's not just the surface, who knows the long term effect of it all piling up on the seafloor where there is nothing we can do about it. (Although, if it were to go anywhere, I'm betting sinking a few miles down would be better than being at the surface when it comes to environmental impact, but I'm unsure.)