At closure, the owner or operator shall remove all hazardous waste and hazardous waste residues (including, but not limited to, ash) from the thermal treatment process or equipment.
Wis. Admin. Code Department of Natural Resources NR 665.0381
At closure, as throughout the operating period, unless the owner or operator can demonstrate, in accordance with s. NR 661.0003(3) or (4), that any solid waste removed from the thermal treatment process or equipment is not a hazardous waste, the owner or operator becomes a generator of hazardous waste and shall manage it in accordance with all applicable requirements of chs. NR 662 and 663 and this chapter.