NR 207.12(3)(b)5.5. The permittee has installed the treatment facilities required to meet the effluent limitations in the previous permit and has properly operated and maintained the facilities, but has nevertheless been unable to achieve the previous effluent limitations. In such a case, the effluent limitation in the reissued, revoked and reissued, or modified permit may be relaxed to reflect the level of pollutant control actually achieved. However, in no case may the limitation be less stringent than applicable effluent guidelines in effect at the time of reissuance or modification. NR 207.12 NoteNote: These exceptions are listed in 33 USC 1342(o)(2). NR 207.12(4)(4) Relaxing an interim effluent limitation or an elg-based limitation or standard. Interim effluent limitations, standards, and conditions and ELG-based effluent limitations and standards that have taken effect in a permit may be relaxed in a reissued, revoked and reissued, or modified permit if the requirements in sub. (1) (a) and (b) are met and both of the following are met: NR 207.12(4)(a)(a) Circumstances upon which the previous permit was based have materially and substantially changed since the time the permit was issued. NR 207.12(4)(b)(b) Changes have occurred that would constitute cause for a permit modification or revocation and reissuance under ch. NR 203. NR 207.12 HistoryHistory: CR 17-002: cr. Register April 2018 No. 748, eff. 5-1-18; correction in (3) (a) 2. b. under s. 13.92 (4) (b) 7., Stats., Register April 2018.