---
kind: "section"
citation: "40 C.F.R. § 403.18"
title: "40"
number: "403.18"
heading: "Modification of POTW pretreatment programs."
url: "https://uscodex.org/cfr/40/403.18"
---

# §403.18. Modification of POTW pretreatment programs.

- (a) **General.** Either the Approval Authority or a POTW with an approved POTW Pretreatment Program may initiate program modification at any time to reflect changing conditions at the POTW. Program modification is necessary whenever there is a significant change in the operation of a POTW Pretreatment Program that differs from the information in the POTW's submission, as approved under [§ 403.11](/cfr/40/403.11.md).
- (b) **Substantial modifications defined.** Substantial modifications include:
  - (1) Modifications that relax POTW legal authorities (as described in [§ 403.8(f)(1)](/cfr/40/403.8.md?p=f-1)), except for modifications that directly reflect a revision to this part 403 or to [40 CFR chapter I](/cfr/40/chI.md), subchapter N, and are reported pursuant to [paragraph (d)](#d) of this section;
  - (2) Modifications that relax local limits, except for the modifications to local limits for pH and reallocations of the Maximum Allowable Industrial Loading of a pollutant that do not increase the total industrial loadings for the pollutant, which are reported pursuant to [paragraph (d)](#d) of this section. Maximum Allowable Industrial Loading means the total mass of a pollutant that all Industrial Users of a POTW (or a subgroup of Industrial Users identified by the POTW) may discharge pursuant to limits developed under [§ 403.5(c)](/cfr/40/403.5.md?p=c);
  - (3) Changes to the POTW's control mechanism, as described in [§ 403.8(f)(1)(iii)](/cfr/40/403.8.md?p=f-1-iii);
  - (4) A decrease in the frequency of self-monitoring or reporting required of industrial users;
  - (5) A decrease in the frequency of industrial user inspections or sampling by the POTW;
  - (6) Changes to the POTW's confidentiality procedures; and
  - (7) Other modifications designated as substantial modifications by the Approval Authority on the basis that the modification could have a significant impact on the operation of the POTW's Pretreatment Program; could result in an increase in pollutant loadings at the POTW; or could result in less stringent requirements being imposed on Industrial Users of the POTW.
- (c) **Approval procedures for substantial modifications.**
  - (1) The POTW shall submit to the Approval Authority a statement of the basis for the desired program modification, a modified program description (see [§ 403.9(b)](/cfr/40/403.9.md?p=b)), or such other documents the Approval Authority determines to be necessary under the circumstances.
  - (2) The Approval Authority shall approve or disapprove the modification based on the requirements of [§ 403.8(f)](/cfr/40/403.8.md?p=f) and using the procedures in [§ 403.11(b) through (f)](/cfr/40/403.11.md?p=b..f), except as provided in [paragraphs (c)](#c) (3) and (4) of this section. The modification shall become effective upon approval by the Approval Authority.
  - (3) The Approval Authority need not publish a notice of decision under [§ 403.11(e)](/cfr/40/403.11.md?p=e) provided: The notice of request for approval under [§ 403.11(b)(1)](/cfr/40/403.11.md?p=b-1) states that the request will be approved if no comments are received by a date specified in the notice; no substantive comments are received; and the request is approved without change.
  - (4) Notices required by [§ 403.11](/cfr/40/403.11.md) may be performed by the POTW provided that the Approval Authority finds that the POTW notice otherwise satisfies the requirements of [§ 403.11](/cfr/40/403.11.md).
- (d) **Approval procedures for non-substantial modifications.**
  - (1) The POTW shall notify the Approval Authority of any non-substantial modification at least 45 days prior to implementation by the POTW, in a statement similar to that provided for in [paragraph (c)(1)](#c-1) of this section.
  - (2) Within 45 days after the submission of the POTW's statement, the Approval Authority shall notify the POTW of its decision to approve or disapprove the non-substantial modification.
  - (3) If the Approval Authority does not notify the POTW within 45 days of its decision to approve or deny the modification, or to treat the modification as substantial under [paragraph (b)(7)](#b-7) of this section, the POTW may implement the modification.
- (e) **Incorporation in permit.** All modifications shall be incorporated into the POTW's NPDES permit upon approval. The permit will be modified to incorporate the approved modification in accordance with [40 CFR 122.63(g)](/cfr/40/122.63.md?p=g).

## Notes

### Amendments

[62 FR 38414, July 17, 1997]

### Authority

Authority: 33 U.S.C. 1251 et seq.

### Source

Source: 46 FR 9439, Jan. 28, 1981, unless otherwise noted.

### Amendments

[62 FR 38414, July 17, 1997]