AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice of data availability; request for public comment.

SUMMARY:

The Environmental Protection Agency (EPA) is announcing the availability of new modeling, meteorological and emissions information and data contained in a package submitted to EPA by the Commonwealth of Pennsylvania on February 5, 2020 in support of the Indiana, Pennsylvania state implementation plan (SIP, or Attainment Plan) for the 2010 sulfur dioxide (SO₂) primary National Ambient Air Quality Standard (NAAQS). EPA will be evaluating this information as well as any public comments received to take final action on the Attainment Plan. The modeling and large data files submitted are not provided in the docket but are available upon request by contacting the person named in the FOR FURTHER INFORMATION CONTACT section.

DATES:

Written comments must be received on or before April 8, 2020.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R03-OAR-2017-0615 at https://www.regulations.gov, or via email to spielberger.susan@epa.gov. For comments submitted at Regulations.gov, follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov. For either manner of submission, EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be confidential business information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission (i.e., on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit http://www2.epa.gov/​dockets/​commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT:

Megan Goold, Planning & Implementation Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection Agency, Region III, 1650 Arch Street, Philadelphia, Pennsylvania 19103. The telephone number is (215) 814-2027. Ms. Goold can also be reached via electronic mail at goold.megan@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

EPA proposed approval of the Attainment Plan for the Indiana, Pennsylvania Nonattainment Area for the 2010 SO₂ NAAQS on July 13, 2018. 83 FR 32606. As part of approving the Attainment Plan, EPA also proposed to approve into the Pennsylvania SIP SO₂ emission limits and associated compliance parameters for Keystone, Conemaugh, Homer City and Seward Generating Stations. The public comment period for EPA's proposal closed on August 13, 2018. During the public comment period, EPA received from one commenter new information and analysis purporting to show that, using an alternative receptor grid, the critical emission values (CEVs) for Seward and Conemaugh Stations modeled a violation of the standard within the boundaries of the nonattainment area (NAA). In response, the Pennsylvania Department of Environmental Protection (PADEP) opted to provide EPA with supplemental information to provide further support for their submitted Attainment Plan. The supplemental information includes: (1) A supplemental air dispersion modeling report, (2) Supplemental air dispersion modeling data, (3) Supplemental air dispersion modeling protocol, (4) A meteorological monitoring plan, (5) Meteorological monitoring data, (6) Meteorological monitoring quality assurance, quality control, and audit reports, (7) Clean Air Markets Division (CAMD) emission data for 2010-2018, and (8) Continuous Emissions Monitoring (CEM) data for 2010-2019 (3rd Quarter).

PADEP's supplemental modeling report provides additional modeling using the newly provided site specific meteorological data to support the SO₂ emission limits established in the original attainment plan. The study supplements the modeling submitted in 2017 (see Docket EPA-R03-OAR-2017-0615-0018 which can be located via https://www.regulations.gov) to focus on the area in the NAA near Conemaugh and Seward stations. The meteorological data collection spanned the 13-month period of August 1, 2015 through August 31, 2016. Due to better SOnic Detection And Radar (SODAR) data capture percentages for the September 1, 2015 through August 31, 2016 period, this 12-month period was used for this supplemental modeling analysis. PADEP used AERMOD dispersion model 16 (Version 19191), current as of August 2019, to evaluate air quality impacts from the emission sources of interest. The South Fayette, Pennsylvania monitor, which is located about 62 kilometers to the west-southwest of the Indiana County NAA, was used to determine the uniform regional background component for the NAAQS SO₂ modeling. The most recent 3-year period (2016-2018) of emissions data were used in the modeling analysis and details on the emissions processing are provided in the submittal, which can be found in the docket for this notice.

The modeling was used to define CEVs for Seward and Conemaugh Generating Stations that show 99th percentile peak daily 1-hour maximum concentrations (“design concentrations”) complying with the 1-hour SO₂ NAAQS. For the Seward and Conemaugh Generating Stations, longer-term emission rates that are discounted from the 1-hour CEV rates were derived. Different averaging times were selected to best fit the emission source profiles at each plant. Conemaugh emission rates are based upon a 3-hour block emission average, and the Seward emission rate is based upon a rolling 30-day average. The current SO₂ emission limits for the modeled emission sources at the Conemaugh and Seward Stations are lower than the longer-term emission rates that demonstrate attainment with the NAAQS through modeling.

To demonstrate that Seward's rolling 30-day emission limit is protective of the NAAQS, PADEP submitted randomly reassigned emissions (RRE) modeling. One hundred AERMOD simulations were run using randomly reassigned 1-hour emission rates for Seward's emissions along with constant CEV 1-hour emission rates for the remaining three SO₂ sources in the NAA plus regional background (South Fayette monitor for 2016-2018 as discussed in Section 4.7 of the Modeling Report). For each of the 100 modeling runs with one year of on-site meteorology, the 99th percentile peak daily 1-hour maximum at each receptor resulted in design concentrations that comply with the NAAQS. The highest 99th percentile daily maximum SO₂ concentration of the 100 model simulations was 190.05 micrograms per meter cubed (μg/m ³) (this occurred in simulation run 44) and is less than the NAAQS (196.4 μg/m ³).

The supplemental modeling purports to demonstrate that a lower CEV for Seward Generating Station demonstrates attainment compared to the CEV provided in the original attainment plan. The rolling 30-day emission limit for Seward has remained unchanged. The newly submitted RRE modeling purportedly demonstrates that the rolling 30-day emission limit for Seward is protective of the NAAQS. The CEV for Conemaugh Generating Station has not changed from the original Attainment Plan as a result of the supplemental modeling analysis, and therefore no additional analysis was provided in support of the source's longer term 3-hour block limit.

EPA is seeking comment on the Pennsylvania supplemental information submitted on February 5, 2020 as supporting analysis that shows the previously-established longer term emission limits for Seward and Conemaugh Generating Stations demonstrate attainment of the 2010 SO₂ NAAQS in the Nonattainment Area. EPA is not seeking comment on any other aspect of the Attainment Plan, which has already gone through the public comment process from July 13, 2018 through August 13, 2018.