Iowa Admin. Code r. 567-62.7
An effluent limitation less stringent than the effluent limitation guideline (adopted by reference in 567-624. (455B)) representing the degree of effluent reduction achievable by application of the best practicable control technology currently available may be allowed in an NPDES permit if the factors relating to the equipment or facilities involved, the process applied, or other such factors related to the discharger are fundamentally different from the factors considered by the administrator in the establishment of the guidelines. An individual discharger or other interested person may submit evidence concerning such factors to the director. On the basis of such evidence or other available information and in accordance with 40 CFR 12531., the director will make a written finding that such factors are or are not fundamentally different from the facility compared to those specified in the development document. Any such less stringent effluent limitations must, as a condition precedent, be approved by the administrator.
Iowa Admin. Code r. 567-62.7