At closure, all hazardous waste and hazardous waste residues shall be removed from treatment processes or equipment, discharge control equipment and discharge confinement structures.
Wis. Admin. Code Department of Natural Resources NR 665.0404
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 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.