Grading & Drainage: Altadena vs Downey
How do grading & drainage rules compare between Altadena, CA and Downey, CA?
Downey 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 →Downey, CA
Los Angeles County
Grading permits are required in Downey for significant earth-moving projects. The Engineering Division reviews drainage plans to ensure proper stormwater conveyance and prevent flooding of adjacent properties.
View full Downey rules →Key Facts Comparison
| Fact | Altadena | Downey |
|---|---|---|
| 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) | - |
| Permit | - | Required for grading work |
| Review | - | Engineering Division approval |
| Drainage | - | Must not impact neighbors |
| County | - | LA County standards apply |
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).
Downey FAQ
Do I need a grading permit?
Generally required for earth-moving over 50 to 100 cubic yards or changes to existing drainage patterns. Small landscaping projects are usually exempt.
My neighbor changed their grading and water flows onto my property. What can I do?
Contact Downey code enforcement. Redirecting drainage onto neighboring properties violates most municipal codes. The neighbor may be required to restore proper drainage.
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