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The "70% Rule" Visualizer

Chapter 9 of the EPA Guide requires "70% of native background density" for final stabilization.

Current Coverage70%

100%

Pass: Stabilized

Vegetation meets the 70% requirement (70% needed).

Simulation: 70% Coverage

What is Final Stabilization?

Before you can file a Notice of Termination (NOT) to end your SWPPP coverage (and stop paying permit fees), you must achieve "Final Stabilization."

The EPA defines this as achieving a uniform perennial vegetative cover with a density of 70% of the native background vegetative cover for the area.

The "Native Background" Nuance

Many contractors mistakenly think they need 70% total coverage (like a lush lawn). This is incorrect. You need 70% of what naturally grows there.

  • Example 1 (Lush Area): If the undisturbed land next door has 100% grass cover, you need 70% cover to close your permit.
  • Example 2 (Arid Area): If you are building in the desert where natural vegetation is only 40% dense, you only need to achieve 28% density (0.70 × 40%) to be compliant.

How to document this?

When you submit your NOT, you should include:

  1. Photos of the stabilized area.
  2. Photos of the adjacent "native background" area for comparison.
  3. A brief narrative explaining your calculation.

Need help tracking stabilization?

RunOffTrack allows you to log "Percent Stabilized" in your weekly inspection reports, creating a timeline of growth to prove compliance when you file your NOT.

Start Tracking Vegetation →