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Notice of Public Comment Period – Draft Source Category Permit 7043-SC-R2

Friday, December 15, 2023


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

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 natural gas-fired emergency engines subject to the federal New Source Performance Standard (NSPS) for spark ignition internal combustion engines (40 CFR 60, Subpart JJJJ) in the District of Columbia. This source category permit will be designated Permit No. 7043-SC-R2.

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

1.   The maximum engine power is less than or equal to 25 horsepower (HP) [19 mechanical kilowatts (kWm)] and it was manufactured on or after July 1, 2008;

2.   The manufacturer participates in the voluntary manufacturer certification program described in 40 CFR 60, Subpart JJJJ and the date of manufacture of the emergency engine is after January 1, 2009; or

3.   The emergency engine was ordered after June 12, 2006, was manufactured on or after January 1, 2009, and has a maximum engine power greater than 25 HP (19 kWm).

This permit will ultimately replace permit No. 7043-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 60.4233 for the appropriate engine type. Any engine subject to a Family Emission Limit (FEL) shall comply with any such limits as specified on the applicable 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 60.4233 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 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 § 205 (non-attainment New Source Review). However, based on past permitting activity implemented by AQD, very few natural gas-fired emergency engines in the District of Columbia exceed 2,000 horsepower (hp) in mechanical output. Based on a limitation in the permit of 500 hours per year of total operations, conservative emission factors for spark ignition engines, and a 2,000 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)


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 available in 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.