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Notice of Public Comment Period – Draft Source Category Permit 7048-SC-R2

Friday, December 15, 2023


Proposed Air Quality Source Category Permit Renewal and Revision to Construct and Operate Stationary Diesel-Fired Emergency Engines Subject to NSPS Subpart IIII

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 and revised source category permit to construct and operate certain diesel-fired emergency engines subject to the federal New Source Performance Standard (NSPS) for compression ignition internal combustion engines (40 CFR 60, Subpart IIII) in the District of Columbia. This source category permit will be designated Permit No. 7048-SC-R2.

This source category permit will cover only a subset of stationary diesel-fired emergency engines that trigger NSPS Subpart IIII applicability based on one of the following triggers:

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;

This permit will ultimately replace permit No. 7048-SC-R1, issued September 27, 2019, and scheduled to expire on September 26, 2024. It will not, however, immediately supersede the previous permit for those already covered by that permit. This will give applicants time to submit applications to be covered by the new permit.

In addition to establishing a new five-year duration for the source category permit, the proposed permit also updates permit language, primarily to address revisions to the District’s Visible Emissions regulation (20 DCMR § 606) and the District’s Odorous or Other Nuisance Air Pollutants Regulation (20 DCMR § 903).

The proposed permit complies with the current District and federal laws and regulations governing this source category.

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

a.   Emissions from the engine shall not exceed those specified in 40 CFR 60.4205 for the appropriate engine type. Any engine subject to a Family Emission Limit (FEL) shall comply with any such limits as specified on an EPA Certificate of Conformity. If the engine is certified as a non-emergency engine, the engine shall comply with the standards to which it has been certified. [40 CFR 60.4205 and 20 DCMR 201]

b.   Visible emissions shall not be emitted into the outdoor atmosphere from the engine, except that discharges shall be permitted for two (2) minutes during any start-up, cleaning, adjustment of combustion or operational controls, or regeneration of emissions control equipment; provided, that such discharges shall not exceed twenty-seven percent (27%) opacity (unaveraged). [20 DCMR 606.1 and 606.2(d)]

c.   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]

Violation of the requirements of this condition that occur as a result of unavoidable malfunction, despite the conscientious employment of control practices, shall be an affirmative defense for which the owner or operator shall bear the burden of proof. A malfunction shall not be considered unavoidable if the owner or operator could have taken, but did not take, appropriate steps to eliminate the malfunction within a reasonable time, as determined by the Department. [20 DCMR 903.13(b)]

Note: This condition is District enforceable only.

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 install 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 revised 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) 498-8143. Copies of the draft permit and related technical support memorandum are also availablein the attachments section below.

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

Washington DC 20002

[email protected]


No comments or hearing requests submitted after January 16, 2024 will be accepted.

For more information, please contact Stephen S. Ours at (202) 498-8143.