At closure the owner or operator shall remove all hazardous waste and hazardous waste residues (including, but not limited to, ash, scrubber waters and scrubber sludges) from the incinerator site.
Wis. Admin. Code Department of Natural Resources NR 664.0351
At closure, as throughout the operating period, unless the owner or operator can demonstrate, according to s. NR 661.0003(4), that the residue removed from the incinerator is not hazardous waste, the owner or operator becomes a generator of hazardous waste and shall manage it according to the applicable requirements of chs. NR 662 to 666.