What would happen if this thing got washed out?

Hypothetically speaking, let's say a fiery but mostly peaceful asteroid impact in the Pacific created a tsunami that shoved the lid to the side and washed the crater's contents into the sea, what would the short and long-term effects of that be? We're talking about 73,000 cubic meters of topsoil contaminated by a series of 66 atomic bomb blasts and one hydrogen bomb blast sitting just eight meters above sea level. What could go wrong?