Do Georgia stormwater / BMP rules apply to residential remodels?

Stormwater rules absolutely apply to residential remodels once the project crosses certain disturbance and impervious-cover thresholds. The governing document is the Georgia Stormwater Management Manual, commonly called the Blue Book (Volumes 1 and 2 covering technical standards and design) and the Red Tub (the local enforcement and inspection volumes adopted by individual jurisdictions). Authority traces back to the Georgia Erosion and Sedimentation Act of 1975 (O.C.G.A. 12-7-1 through 12-7-22) and the Georgia Water Quality Control Act, with delegated enforcement at the county and municipal level under the National Pollutant Discharge Elimination System (NPDES) MS4 permits issued by the Georgia Environmental Protection Division.

For residential work, the trigger thresholds are concrete. Any project disturbing 5,000 square feet or more (whichever is smaller of the cumulative disturbed area or the new impervious cover) must file a Land Disturbance Permit with the local jurisdiction, install Best Management Practices (BMPs), and meet post-construction water-quality and detention requirements. Common BMPs include silt fencing along the downhill perimeter, construction entrance pads to keep mud off public streets, sediment traps or basins for slopes, vegetated buffers, inlet protection on existing storm drains, and stabilization of disturbed areas within 14 days of inactivity. Post-construction, projects creating 5,000 sq ft or more of new impervious cover must provide water-quality treatment of the first 1.2 inches of rainfall and channel-protection volume for the 1-year, 24-hour storm.

In the field, the threshold matters. A single-room addition under 500 sq ft of new impervious typically clears with a generic erosion-control permit and a silt fence. An ADU plus driveway extension plus pool plus hardscape can easily cross the 5,000-sq-ft threshold and force a full stormwater package with engineered detention, infiltration trench, or rain-garden BMPs designed by a licensed professional engineer. The City of Atlanta also imposes its own Post-Construction Stormwater Management Ordinance under Code Chapter 74, which adds runoff-reduction targets on top of state rules.