40 CFR § 121.10 - Modification to a grant of certification.

---
identifier: "/us/cfr/t40/s121.10"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 121.10 - Modification to a grant of certification."
title_number: 40
title_name: "Protection of Environment"
section_number: "121.10"
section_name: "Modification to a grant of certification."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "D"
subchapter_name: "WATER PROGRAMS"
part_number: "121"
part_name: "STATE CERTIFICATION OF ACTIVITIES REQUIRING A FEDERAL LICENSE OR PERMIT"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "33 U.S.C. 1251"
regulatory_source: "88 FR 66661, Sept. 27, 2023, unless otherwise noted."
cfr_part: "121"
---


# 121.10 Modification to a grant of certification.

(a) Provided that the Federal agency and the certifying authority agree in writing that the certifying authority may modify a grant of certification (with or without conditions), the certifying authority may modify only the agreed-upon portions of the certification. The certifying authority is not required to obtain the Federal agency's agreement on the language of the modification.

(b) The certifying authority shall not, through a modification pursuant to paragraph (a) of this section:

(1) Revoke a grant of certification (with or without conditions); or

(2) Change a grant of certification (with or without conditions) into a denial or waiver of certification.