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True Minor Source Definition

What is a True Minor Source?

A source that does not have the physical or operational capacity to emit major amounts (even if the source owner and regulatory agency disregard any enforceable limits). The major amounts are as follows:

  1. Criteria pollutants in Attainment or Nonattainment Areas = 100 tons pollutant per year. Lower thresholds apply in Nonattainment Areas, but only for the pollutant that is in Nonattainment (see below)
  2. Nonattainment area designation voc or nox Threshold in tons/yr
    Lower Major Source Thresholds for Nonattainment Areas
    Marginal 100 tons/yr
    Moderate 100 tons/yr
    Serious 50 tons/yr
    *Ozone Transport Region (other than severe or extreme) 50 tons/yr
    (VOC only)

    *Arlington County, Fairfax County, Loudoun County, Prince William County, Stafford County, Alexandria City, Fairfax City, Falls Church City, Manassas City, and Manassas Park City

  3. Toxic pollutants = 10 tons pollutant per year individually OR 25 tons pollutants per year combined

Example 1: True Minor Source

A new facility located in an Attainment Area consists of the following equipment:

  • A tertiary stone crusher rated at 370 tons/hr
  • A screen rated at 500 tons/hr

Uncontrolled Emission Calculations:

PM, PM-10, and PM 2.5 uncontrolled emissions need to be calculated using uncontrolled emission factors from AP-42, Section 11.19.2.

  • Crusher

PM10 Crusher Formula

Assume PM 2.5 = PM10

  • Screen

PM10 Screen Formula

Assume PM2.5=PM10

 Pollutant  PTE Emissions (tons/yr) Major Source Threshold (Tons/yr)   Less Than Major Source Threshold?
 PM  63.6  100  Yes
 PM10  23.0  100  Yes
 PM2.5  23.0  100  Yes

Example #2: NOT a true minor source

A new facility located in an Attainment Area consists of a coating operation with a spray gun rated at 10 gallons (gal) coating/hr. The coating specifications from the Material Safety Data Sheet (MSDS) are:

  • VOC Content = 6.0 lb VOC/gal coating
  • Toluene Content = 2.0 lbs toluene/gal coating
  • Solids Content = 75%
  • Transfer Efficiency = 60%
  • Density of Coating = 7.0 lbs coating/gal coating

Uncontrolled Emission Calculations:

PM, VOC, and toluene uncontrolled emissions need to be calculated.

  • PM (Assume PM = PM-10 = PM 2.5)

Uncontrolled Emissions formula for PM10

  • VOC

Uncontrolled emissions formula for VOC

  • Toluene

Uncontrolled emissions formula for toluene

  Pollutant PTE Emissions (tons/yr)    Major Source Threshold (tons/yr) Less Than Major Source Threshold? 
PM, PM-10, PM2.5   92.0 (each)   100 (each)   Yes
  VOC   262.8   100   No
  Toluene   87.6   10   No

Please contact your regional office if you need assistance to determine if a source is a true minor.

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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000

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