35 Ill. Adm. Code 203.1390
Stack in Existence
Section 203.1390Â Stack in
Existence
"Stack in existence" means that the owner or
operator had begun, or caused to begin, a continuous program of physical
on-site construction of the stack or entered into binding agreements or
contractual obligations, that could not be cancelled or modified without substantial
loss to the owner or operator, to undertake a program of construction of the
stack to be completed within a reasonable time.