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khammond on DSKJM1Z7X2PROD with PROPOSALS

Federal Register / Vol. 86, No. 165 / Monday, August 30, 2021 / Proposed Rules are identified as maintenance-only receptors. In addition, those sites that are currently measuring ozone concentrations below the level of the applicable NAAQS but are projected to be nonattainment based on the average design value and that, by definition, are projected to have a maximum design value above the standard are also identified as maintenance-only receptors.
To evaluate future air quality in steps 1 and 2 of the interstate transport framework, EPA is using the 2016 and 2023 base case emissions developed under the EPA/MJO/state collaborative emissions modeling platform project as the primary source for base year and 2023 future year emissions data for this proposal.24 Because this platform does not include emissions for 2021, EPA
developed an interpolation technique based on modeling for 2023 and measured ozone data to determine ozone concentrations for 2021. To estimate average and maximum design values for 2021, EPA first performed air quality modeling for 2016 and 2023 to obtain design values in 2023. The 2023
design values were then coupled with the corresponding 2016 measured design values to estimate design values in 2021. Details on the modeling, including the interpolation methodology, can be found in the Air Quality Modeling TSD, found in the docket for this proposal.
To quantify the contribution of emissions from specific upwind states on 2021 8-hour design values for the identified downwind nonattainment and maintenance receptors, EPA first performed nationwide, state-level ozone source apportionment modeling for 2023. The source apportionment modeling provided contributions to ozone from precursor emissions of anthropogenic nitrogen oxides NOX
and volatile organic compounds VOCs in each state, individually. The modeled contributions were then applied in a relative sense to the 2021 average design value to estimate the contributions in 2021 from each state to each receptor.
Details on the source apportionment modeling and the methods for determining contributions in 2021 are in the Air Quality Modeling TSD in the docket.
The 2021 design values and contributions were examined to determine if Connecticut contributes at or above the threshold of one percent of 24 See 86 FR 23054 April 30, 2021. The results of this modeling are included in a spreadsheet in the docket for this action. The underlying modeling files are available for public access in the docket for the Revised CSAPR Update EPAHQOAR2020
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the 2015 ozone NAAQS 0.70 ppb to any downwind nonattainment or maintenance receptor. The data 25
indicate that the highest contribution in 2021 from Connecticut to a downwind nonattainment or maintenance receptor is 0.44 ppb to a nonattainment receptor in Richmond County, New York monitoring site 360850067. The data also show modeled ozone contributions from Connecticut to the design values of a larger set of monitoring sites independent of attainment status and indicate that the highest projected contribution in 2021 from Connecticut to any of these sites is 3.51 ppb to Kent County in Rhode Island monitoring site 440030002; 378 on the Design Values and Contributions spreadsheet. While Connecticuts modeled contribution to the Kent County monitor exceeds one percent of the 2015 ozone NAAQS, EPAs analysis at step 1 does not identify the Kent County monitor as a downwind area that may have problems maintaining the 2015 ozone NAAQS.
The Kent County monitors projected average design value in 2021 is 65.5
ppb. The updated modeling for 2021
also shows that Connecticut is no longer projected to be linked to the Suffolk County monitoring site, since this monitor is no longer projected to be a nonattainment or maintenance receptor.
EPA also analyzed ozone precursor emissions trends in Connecticut to support the findings from the air quality analysis. In evaluating emissions trends, we first reviewed the information submitted by the state and then reviewed additional information available to the Agency. We focused on state-wide emissions of NOX and VOCs.26 Emissions from mobile sources, electric generating units EGUs, industrial facilities, gasoline vapors, and chemical solvents are some of the major anthropogenic sources of ozone precursors. This evaluation looks at both past emissions trends, as well as projected trends.
As shown in Table 1, for Connecticut, annual total NOX and VOC emissions are projected to decline between 2016
and 2023 by 31 percent and 2 percent, respectively. The projected reductions are a result of the implementation of existing control programs that will continue to decrease NOX and VOC
25 The data are given in the Air Quality Modeling Technical Support Document for the Revised Cross-State Air Pollution Rule Update and Ozone Design Values and Contributions Revised CSAPR Update.xlsx, which are included in the docket for this action.
26 This is because ground-level ozone is not emitted directly into the air but is formed by chemical reactions between ozone precursors, chiefly NOX and VOCs, in the presence of sunlight.
See 86 FR 23054, 23063.

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emissions in Connecticut, as indicated by EPAs most recent 2021 and 2023
projected emissions.
As shown in Table 2, on-road and nonroad mobile source emissions collectively comprise a large portion of Connecticuts total anthropogenic NOX
and VOCs. For example, in 2019, NOX
emissions from mobile sources in Connecticut comprised 62 percent of total NOX emissions and 38 percent of total VOC emissions.
The large decrease in NOX emissions between 2016 emissions and projected 2023 emissions in Connecticut is primarily driven by reductions in emissions from on-road and nonroad mobile sources. EPA projects that both VOC and NOX emissions will continue declining to 2023 as newer vehicles and engines that are subject to the most recent, stringent mobile source standards replace older vehicles and engines.27
In summary, based on the projected downward trend in projected future emissions trends, in combination with the historical decline in actual emissions, there is no evidence to suggest that the overall emissions trend demonstrated in Table 2 would suddenly reverse or spike in 2021
compared to historical emissions levels or those projected for 2023. Further, there is no evidence that the projected ozone precursor emissions trends beyond 2021 would not continue to show a decline in emissions. In addition, EPA followed its normal practice of including in our modeling only changes in NOX or VOC emissions that result from final regulatory actions.
Any potential changes in NOX or VOC
emissions that may result from possible future or proposed regulatory actions are speculative.
This downward trend in emissions in Connecticut adds support to the air quality analyses presented above for the state and indicates that the contributions from emissions from sources in Connecticut to ozone receptors in downwind states will 27 Tier 3 Motor Vehicle Emission and Fuel Standards 79 FR 23414, April 28, 2014; Mobile Source Air Toxics Rule MSAT2 72 FR 8428, February 26, 2007, Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements 66 FR 5002, January 18, 2001; Clean Air Nonroad Diesel Rule 69 FR 38957, June 29, 2004; Locomotive and Marine Rule 73 FR 25098, May 6, 2008; Marine Spark-Ignition and Small Spark-Ignition Engine Rule 73 FR 59034, October 8, 2008; New Marine Compression-Ignition Engines at or Above 30 Liters per Cylinder Rule 75 FR
22895, April 30, 2010; and Aircraft and Aircraft Engine Emissions Standards 77 FR 36342, June 18, 2012.

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