How Much Soil Removal Is Enough?

If you’re a homeowner in Altadena or Pacific Palisades (or any area affected by wildfire) and want to plant a garden—especially for growing food—after fire-related debris has been removed, you’ll want to go beyond the standard 6 inches removed by the USACE for safety. Here’s what experts typically recommend:

🌱 Recommended Soil Removal Depth for Garden Safety After Wildfires

✅ Minimum Safe Depth: 12–18 inches

• Most environmental health agencies recommend removing at least 12 inches, and up to 18 inches of soil, particularly in areas intended for food production.
• This is because:
  • Heavy metals (like arsenic, lead, and cadmium) and persistent organic pollutants (like dioxins and PAHs) can leach deeper into the soil than the standard 6-inch cleanup.
  • Roots of vegetables (especially root crops like carrots, potatoes, etc.) may reach below 6 inches.

🔬 Soil Contaminants to Be Aware Of:

• Arsenic
• Lead
• PAHs (polycyclic aromatic hydrocarbons)
• Dioxins
• Asbestos fibers (if older buildings were destroyed)

🧪 What You Should Do First:

1. Conduct a Soil Test
   • Use a lab that tests for heavy metals, hydrocarbons, and toxins.
   • One option: UMass Soil Lab or Logan Labs.
   • Tell them you’re testing post-fire soil for garden use.
2. If Contaminants Are Present:
   • Excavate and replace 12–18 inches of soil with clean topsoil and compost.
   • Or consider raised garden beds with a geotextile barrier between the contaminated and clean soil.

🌿 Pro Tip for Home Gardening:

• Use raised beds with at least 18 inches of clean soil, even after removal, if you’re unsure about deep contamination.
• Add compost and organic matter to restore soil health and microbial activity.

🛡️ Summary