Grading & Drainage: Castaic vs Downey
How do grading & drainage rules compare between Castaic, CA and Downey, CA?
Castaic and Downey have similar restriction levels.
Castaic, 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 Castaic 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 | Castaic | Downey |
|---|---|---|
| Grading Permit | Required from Building & Safety | - |
| Flood Control | LACFCD manages regional system | - |
| Retaining Walls | Permit if over 4 ft | - |
| Coastal | Terracing and native landscaping | - |
| 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.
Castaic 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.
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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