section 90

What is the purpose of Section 90?

To reduce and prevent PM10 fugitive dust emissions from open areas and vacant lots.

Where does Section 90 apply?

• PM10 nonattainment areas

• PM10 maintenance plan areas

• Apex Valley (Hydrographic Areas 216 and 217)

Who is responsible for compliance?

Owners and/or operators of open areas and vacant lots.

Who is exempt from Section 90?

• Normal farm cultural practices

• Raising fowl or animals

• Most stationary sources

What triggers Section 90 requirements?

When an open area or vacant lot:

• is 5,000 square feet or larger,

• and becomes disturbed by vehicles, off-road vehicles, dumping, or other activities.

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How long does an owner/operator have to implement control measures?

30 calendar days from discovery of disturbance.

Name common control measures under Section 90.

• Water

• Gravel

• Dust palliatives

• Barriers

• Fences

• Gates

• Curbs

• Signs

• Approved alternative methods

Why are barriers and fencing used?

To prevent vehicle trespassing and further soil disturbance.

What is a dust palliative?

A dust suppressant applied to stabilize soil and reduce fugitive dust emissions.

What are the 3 stabilization standards?

• Drop Ball Test (visible crust)

• Rock Test Method (≥20% cover)

• Threshold Friction Velocity (TFV ≥100 cm/sec)

What is the passing TFV value?

100 cm/sec or higher.

What percent non-erodible cover is required?

20% or greater.

What does the Drop Ball Test evaluate?

Whether a protective soil crust exists.

What ball is used?

Steel ball

How high is the ball dropped?

1 foot

What is considered a passing drop?

The ball does not sink and the crust is not pulverized.

Why use a blind over-the-shoulder toss?

To ensure random, unbiased sampling.

How many drops are performed per survey area?

3 drops.

How many drops must pass?

At least 2 out of 3.

How many survey areas are required?

At least 3 survey areas.

What happens if one survey area fails?

The representative surface fails the Drop Ball Test.

What is a representative surface?

A distinct surface type on a site.

Examples:

• Gravel

• Crusted soil

• Loose fine soil

Why are representative surfaces important?

Different surface types must be tested separately.

What does the Rock Test Method evaluate?

The amount of non-erodible cover protecting the soil.

What qualifies as a non-erodible element?

Objects larger than 1 cm that remain in place during wind events.

Examples:

• Rocks

• Stones

• Glass fragments

• Hard soil clumps

Does vegetation count as a non-erodible element?

No.

What is the passing rock cover requirement?

20% or greater.

Why divide overhead area by 2?

To estimate frontal area, which represents wind protection.

What does TFV measure?

The wind strength required to move soil particles.

What does a higher TFV mean?

The surface is more resistant to wind erosion.

Why are correction factors used?

To account for protection provided by non-erodible elements.

What are the TFV correction factors?

• ≥10% cover = 5

• 5–10% cover = 3

• 1–5% cover = 2

• <1% cover = none

What must occur before mechanized weed abatement?

Pre-wet the soil.

What must occur during mechanized weed abatement?

Maintain dust-control measures.

What must occur after mechanized weed abatement?

• Water

• Gravel

• Dust palliative

• Paving

What records must be maintained?

• Control measure used

• Extent of coverage

• Date applied

What does extent of coverage mean?

The amount of area treated or stabilized.

How quickly must records be provided upon request?

Within 24 hours.

How long must records be retained?

At least 1 year.