District of Columbia Department of the Environment

10/10/2025 | Press release | Distributed by Public on 10/10/2025 09:16

Notice of Public Comment Period - Draft Air Quality Permit 6663-R1 - Architect of the Capitol - U.S. Capitol Power Plant

PUBLIC NOTICE

Draft Air Quality Permit 6663-R1, Architect of the Capitol, Operation of an existing 7.5 MW dual fuel-fired (natural gas and No. 2 fuel oil cogeneration system at the U.S. Capitol Power Plant, 25 E Street SE, Washington DC

Notice is hereby given that, pursuant to 20 DCMR § 210, the Air Quality Division (AQD) of the Department of Energy and Environment (DOEE), located at 1200 First Street NE, 5th Floor, Washington DC, proposes to issue air quality permit No. 6663-R1 to the Architect of the Capitol (AOC) to operate an existing cogeneration system that consists of a 78.4 MMBTU/hr combustion turbine with an associated heat recovery steam generator (HRSG) with duct burners with a heat input rating of 71.9 MMBTU/hr when burning natural gas and 68.3 MMBTU/hr when burning diesel oil, at the U.S. Capitol Power Plant (CPP), 25 E Street SE, Washington DC 20003. The contact person for facility is Christopher Potter, Director, Utilities and Power Plant Operations, at (202) 641-6651 or [email protected].

Emissions Estimates:

The maximum potential to emit air pollutants from the cogeneration system has been estimated to be as follows:

Pollutants

Potential to Emit
(tons/12 month rolling period)

Total Particulate Matter (PM Total)1

11.4

Carbon Monoxide (CO)

47.8

Carbon Dioxide (CO2e)

79,150.6

Hexane (C6H14)2

0.51

Oxides of Nitrogen (NOx)

59.2

Sulfur Dioxide (SO2)

4.2

Volatile Organic Compounds (VOC)

6.7

Total Hazardous Air Pollutants (HAPs)

0.9

  1. PM Total is the sum of the filterable PM and condensable PM.
  2. Hexane (C6H14) is the single HAP with the highest potential to emit.

Emission Limitations:

The proposed emission limits for the equipment are as follows (from Condition II of the permit):

  1. When burning natural gas, the combined nitrogen oxides (NOX) emissions from the combustion turbine and associated HRSG unit shall not exceed twenty-five parts per million (25 ppm) at fifteen percent oxygen (15% O2). [20 DCMR 805.4(a)(1)(A)(i), 40 CFR 60.4320(a), and Table 1 of Subpart KKKK of 40 CFR 60]. Note: This is a streamlined permit condition. Compliance with this requirement will ensure compliance with 20 DCMR 805.4(a)(1)(A)(i) and the relevant requirements in 40 CFR 4320(a), and Table 1 of Subpart KKKK of 40 CFR 60.
  2. When burning diesel oil the combined NOX emissions from the combustion turbine and associated HRSG unit shall not exceed forty-two (42) ppmvd at fifteen percent (15%) O2. [20 DCMR 805.4(a)(1)(A)(ii)(II), 40 CFR 4320(a), and Table 1 of Subpart KKKK of 40 CFR 60] Note: This is a streamlined permit condition. Compliance with this requirement will ensure compliance with 20 DCMR 805.4(a)(1)(A)(ii)(II) and the less stringent relevant requirements in 40 CFR 4320(a), and Table 1 of Subpart KKKK of 40 CFR 60.
  3. When burning diesel oil in combination with natural gas, if total heat input is greater than or equal to fifty percent (50%) natural gas, the Permittee shall meet the natural gas emission limit for NOX in Condition II(a). If total heat input is greater than fifty percent (50%) diesel oil, the Permittee shall meet the diesel oil emission limit for NOX in Condition II(b). [20 DCMR 805.4(a)(1)(C) and 40 CFR 60.4325]
  4. The combustion turbine shall comply with one of the following emission limitations for sulfur dioxide (SO2). Compliance shall be demonstrated in accordance with Conditions IV(d) through IV(h) of the permit. [40 CFR 60.4330(a)]

    a. No discharge of gases to the atmosphere which contain SO2 in excess of one hundred ten (110) ng/J gross output, equivalent to 0.90 lb/MWh; or

    b. No fuel may be burned which contains total potential sulfur emissions in excess of twenty-six (26) ng SO2/J heat input, equivalent to 0.060 lb SO2/MMBTU.

  1. Facility-wide emissions of total hazardous air pollutants (HAPs) shall be less than twenty-five (25) tons per year (tpy) on a rolling twelve (12) month basis. [20 DCMR 200.7 and 20 DCMR 201]
  2. Facility-wide emissions of each individual HAP, including hydrogen chloride (HCl), shall be less than ten (10) tpy on a rolling twelve (12) month basis. [20 DCMR 200.7 and 20 DCMR 201]
  3. Total suspended particulate emissions (TSP) (i.e. total filterable particulate matter) from the combustion turbine and duct burners, combined, shall not exceed 0.05 pound per million BTU of heat input to the units, whenever diesel fuel is in use by the duct burners. [20 DCMR 600.1]
  4. Visible emissions shall not be emitted into the outdoor atmosphere from the equipment except that discharges shall be permitted for two (2) minutes during any startup, cleaning, adjustment of combustion or operational controls, or regeneration of emission control equipment, provided that such discharge shall not exceed the following opacities (unaveraged) [20 DCMR 606.1 and 606.2]:

    a. When burning exclusively natural gas, twenty percent (20%); and

    b. When burning fuel oil or a combination of fuel oil and natural gas, twenty seven percent (27%).

  5. 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 Permittee shall bear the burden of proof. A malfunction shall not be considered unavoidable if the Permittee 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.

  6. In addition to complying with the requirements of this permit document, the Permittee shall comply with all Plantwide Applicability Limits (PALs) established for the facility.

The permit application and supporting documentation, along with the draft permit are available for public inspection at AQD and copies may be made available between the hours of 9:00 A.M. and 5:00 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 or [email protected].

Copies of the draft permit and related technical support memorandum are also available at 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 before taking final action on the permit application.

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 November 10, 2025 will be accepted.

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

District of Columbia Department of the Environment published this content on October 10, 2025, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on October 10, 2025 at 15:16 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]