Whose name goes on the manifest?
A manifest names a generator, that generator needs an EPA identification number, and the obligations that follow the waste follow that name — including the ones that outlast the project. For investigation-derived waste the generator is normally the site owner or operator rather than the consultant who produced the drums, but it is settled by the facts of the arrangement and by what the parties agreed, not by convention. The failure mode is specific and common: drums stand on a site for months with nobody's name on them, because the consultant assumed the client would sign and the client assumed the consultant would. Settle it in the contract, before mobilization, along with who pays for characterization and how long the drums may remain on site. It is the cheapest thing on this page to get right and the most expensive to leave open.