Gwinnett County, GA Environmental Rules: Stormwater Management (2026)
Key Facts
- Runoff reduction
- retain first 1 inch of rain
- Water quality
- treat 85% of annual storms
- Pollutant cut
- 80% TSS load reduction
- Scope
- unincorporated Gwinnett development
- Chapter
- 800, effective 9-26-2023
Summary
New development in unincorporated Gwinnett must retain the first inch of rainfall on-site and treat runoff from 85% of a typical year's storms, cutting post-development pollutant loads by 80% under UDO Chapter 800.
800-10.2 Runoff reduction practices shall be sized and designed to retain the first 1-inch of rainfall on the site to the maximum extent practicable. Runoff reduction practices are stormwater best management practices, BMP's, used to disconnect impervious and disturbed pervious surfaces from the stormwater drainage system to reduce the post-construction stormwater runoff rates, volumes, and pollutant loads. Runoff Reduction shall be used where practical, prior to using water quality standards. If the Runoff Reduction requirements cannot be met in whole or part, then the water quality standards shall be used to treat the remainder.
800-10.3 Stormwater management systems shall be designed to detain or treat the runoff from 85% of the storms that occur in an average year and reduce the average annual post-development total suspended solids loadings by 80% in order to meet the water quality requirement. The water quality requirement can be waived if the entire 100% of runoff reduction is provided. Water quality and runoff reduction can also be provided in conjunction in order to meet the water quality requirements outlined in the Gwinnett County Stormwater Management Manual.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 9).
Full Breakdown
Chapter 800 of the Gwinnett UDO requires runoff reduction practices to be sized to retain the first 1-inch of rainfall on a site to the maximum extent practicable, disconnecting impervious and disturbed pervious surfaces from the stormwater system. Where reduction alone can't meet that target, water quality standards apply: stormwater systems must detain or treat runoff from 85 percent of an average year's storms and cut average annual total suspended solids loading by 80 percent, per specifications in the county's Stormwater Management Manual.
Violations & Fines
Developments that don't meet Chapter 800's runoff-reduction and water-quality standards can't get plan approval; the Department of Planning and Development enforces compliance through the development permit and stormwater facility review process under UDO Chapter 120.
Frequently Asked Questions
What stormwater standard applies to new development in unincorporated Gwinnett County?
Who enforces Gwinnett's stormwater rules?
Sources & Official References
Other rules in Gwinnett County
Compare Gwinnett County to another location·View the Georgia environmental rules overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.