Grading & Drainage: Altadena vs South San Gabriel
How do grading & drainage rules compare between Altadena, CA and South San Gabriel, CA?
South San Gabriel has fewer restrictions than Altadena.
Altadena, CA
Los Angeles County
Hillside grading exceeding 2,500 cubic yards cut + fill requires a Conditional Use Permit in Altadena (CSD 22.306.060.B.2.b). Grading during the Oct 15 – Apr 15 rainy season is subject to Public Works erosion-control requirements.
View full Altadena rules →South San Gabriel, CA
Los Angeles County
Grading in unincorporated LA County requires permits from Building & Safety. The LA County Flood Control District manages the regional drainage system with 487 miles of channels and 2,919 miles of storm drain. Retaining walls over 4 ft require permits. Coastal areas have additional requirements for terracing and landscaping.
View full South San Gabriel rules →Key Facts Comparison
| Fact | Altadena | South San Gabriel |
|---|---|---|
| Code Section | Altadena CSD 22.306.060.B + LA County 22.140.240 | - |
| CUP Threshold | 2,500 cy cut + fill | - |
| Haul Route | Required ≥1,000 cy off-site | - |
| Rainy Season | Oct 15 – Apr 15 (extra controls) | - |
| Grading Permit | - | Required from Building & Safety |
| Flood Control | - | LACFCD manages regional system |
| Retaining Walls | - | Permit if over 4 ft |
| Coastal | - | Terracing and native landscaping |
Highlighted rows indicate differences between cities.
Altadena FAQ
Do I need a permit to grade my Altadena hillside lot?
Yes — a Minor Conditional Use Permit is required for any hillside development, and a full CUP if grading exceeds 2,500 cubic yards total (CSD 22.306.060.B).
South San Gabriel FAQ
Do I need a grading permit in unincorporated LA County?
Most grading work requires a permit from Building & Safety. Exemptions exist for less than 50 cubic yards on a single lot that doesn't obstruct drainage. Contact (626) 458-3171 to confirm.
Can I change the drainage on my property?
You cannot redirect concentrated runoff onto neighboring properties. All drainage must go to approved outlets. Significant drainage changes require a grading permit and may need engineering plans.
What reports are needed for hillside grading?
Hillside projects typically require a soils report, geology report, and geotechnical recommendations. The county may require additional studies for slopes, seismic hazards, or landslide-prone areas.
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