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Proposed Air Quality Permit 7115-SC-R1 – Source Category Permit Renewal

Friday, July 24, 2020


Proposed Air Quality Permit 7115-SC-R1 – Source Category Permit Renewal to Operate Existing Stationary Diesel-Fired Emergency Engines Exempt from NSPS Subpart IIII but Subject to NESHAP Subpart ZZZZ at various locations in the District of Columbia

Notice is hereby given that, pursuant to 20 DCMR §§ 200 and 210, the Air Quality Division (AQD) of the Department of Energy and Environment (DOEE), located at 1200 First Street NE, 5th Floor, Washington, DC, intends to issue a renewed source category permit to operate certain diesel-fired emergency engines that are exempt from the federal New Source Performance Standard (NSPS) for compression ignition internal combustion engines (40 CFR 60, Subpart IIII) but subject to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Stationary Reciprocating Internal Combustion Engines (RICE) in the District of Columbia. This source category permit will be designated Permit No. 7115-SC-R1.

To ensure that no engine covered by NSPS Subpart IIII is covered by this permit, certain exclusions related to the engine model year, order date, and manufacture date have been included in the applicability section of the source category permit.

More specifically, this source category permit covers only the operation of existing, emergency internal combustion engines, operated exclusively on diesel fuel, that are exempt from the requirements of 40 CFR 60, Subpart IIII on the basis that they have not been modified or reconstructed as defined in 40 CFR 60.14 or 60.15 and that they do not fall into any of the three following categories:

1.   The model year of the engine is 2007 or later for engines that are not fire pump engines;

2.   The engine is for a fire pump and its model year is equal to or newer than those specified in the following table, based on the size of the engine:

Fire Pump Engine Applicability Table

Engine Power

Starting Applicability Model Year*

Mechanical Kilowatts (kWm)

Horsepower (hp)

kWm <75












*Fire pump engines with a maximum engine power greater than or equal to 37 kWm (50 hp) and less than 450 kWm (600 hp) and a rated speed of greater than 2,650 revolutions per minute (rpm) are covered only three years after the model year listed in this table for the applicable power category.


3.   The engine was ordered by the owner or operator after July 11, 2005 and one of the following is true:

i.    The engine was manufactured after April 1, 2006 and is not a fire pump engine; or

ii.   The engine was manufactured as a certified National Fire Protection Association (NFPA) fire pump engine after July 1, 2006;

In addition, to be covered by this source category permit, an engine must be subject to the requirements of 40 CFR 63, Subpart ZZZZ, on the bases that [See 40 CFR 63.6585 and 40 CFR 63.6590]:

1.   The engine is not located at a major source of hazardous air pollutants (HAPs) (i.e. it is located at an area source of HAPs); and

2.   The engine will not be used for economic or emergency demand response purposes.

The proposed emission limits to be included in the permit are as follows:

a.   Visible emissions shall not be emitted into the outdoor atmosphere from the engine, except that discharges not exceeding forty percent (40%) opacity (unaveraged) shall be permitted for two (2) minutes in any sixty (60) minute period and for an aggregate of twelve (12) minutes in any twenty-four hour (24 hr.) period during start-up, cleaning, adjustment of combustion controls, or malfunction of the equipment [20 DCMR 606.1].

b.   An emission into the atmosphere of odorous or other air pollutants from any source in any quantity and of any characteristic, and duration which is, or is likely to be injurious to the public health or welfare, or which interferes with the reasonable enjoyment of life or property is prohibited. [20 DCMR 903.1]

Applicants who apply for coverage under a source category permit must document that their equipment meets the applicability criteria specified in the permit prior to approval of coverage and authorization to operate the unit under the authority of the source category permit.

Emissions Estimate:

Emissions will vary widely, depending upon the size and age of the equipment to be covered. As such there is no set maximum emissions level except that no unit will be approved under this permit that has a potential to emit greater than 25 tons per year of oxides of nitrogen, the trigger threshold for further regulatory requirements under 20 DCMR §204 (non-attainment New Source Review). However, based on past permitting activity implemented by AQD, very few applicants apply to operate diesel-fired emergency engines in the District of Columbia exceeding 4,000 horsepower (hp) in mechanical output. Based on a limitation in the permit of 500 hours per year of total operations, conservative emission factors for compression ignition engines, and a 4,000 hp engine size, the following represents an estimate of the maximum emissions expected from any emergency engine covered by this source category permit:


Estimated Maximum Annual Emissions (tons/yr)

Total Particulate Matter (PM Total)


Carbon Monoxide (CO)


Oxides of Nitrogen (NOx)*


Volatile Organic Compounds (VOC)


Sulfur Dioxide (SO2)


*Note that there is an applicability limit placed on the permit that no unit having the potential to emit more than 25 tons/year of NOx will be covered by this source category permit.

The draft permit and supporting documentation are available for public inspection at AQD and copies may be made available between the hours of 8:15 A.M. and 4:45 P.M. Monday through Friday. Interested parties wishing to view these documents should provide their names, addresses, telephone numbers and affiliation, if any, to Stephen S. Ours at (202) 535-1747.

Interested persons may submit written comments or may request a hearing on this subject within 30 days of publication of this notice. The written comments must also include the person’s name, telephone number, affiliation, if any, mailing address and a statement outlining the air quality issues in dispute and any facts underscoring those air quality issues. All relevant comments will be considered in issuing the final permit.

Comments on the proposed permit and any request for a public hearing should be addressed to:


Stephen S. Ours  
Chief, Permitting Branch - Air Quality Division

Department of Energy and Environment
1200 First Street NE, 5th Floor

, DC 20002

[email protected]

No comments or hearing requests submitted after August 24, 2020 will be accepted.

For more information, please contact Stephen S. Ours at (202) 535-1747.