Voglio sapere a riguardo di…

Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules to meet the requirements under section 189d was due by December 31, 2016, and reductions were required to occur as of that date. The decline in emissions from 2017 to 2020 shows that reductions did, in fact, occur within the required timeframe. Furthermore, the States demonstration shows that NOX
emissions reductions from 2017 to 2020
are greater than the required five percent per year. Thus, the EPA
proposes to find that the SJV PM2.5 Plan meets the CAA 189d requirement to provide for an annual reduction in PM2.5
or PM2.5 precursor emissions of not less than five percent of the amount of such emissions reported in the most recent inventory prepared for the area.
D. Attainment Demonstration and Modeling 1. Statutory and Regulatory Requirements Section 189b1A of the CAA
requires that each Serious area plan include a demonstration including air quality modeling that the plan provides for attainment of the PM2.5 NAAQS by the applicable attainment date. As discussed in section IV of this proposal, given that the outermost statutory Serious area attainment date for the San Joaquin Valley area i.e., December 31, 2015 has passed and that the EPA has already found that the SJV area failed to attain by that date, the EPA must evaluate the States plan for attainment by a later attainment date. Given that the finding of failure to attain triggered the States obligation to submit a new plan meeting the requirements of section 189d, the EPA is evaluating the SJV PM2.5 Plan in light of the outermost attainment date required in section 189d. That section requires that the attainment date be as expeditious as practicable, but not later than five years following the EPAs finding that the area failed to attain the NAAQS by the applicable Serious area attainment date.
In this case, the State projected such attainment by December 31, 2020, i.e., by the relevant statutory date.
The PM2.5 SIP Requirements Rule explains that the same general requirements that apply to Moderate and Serious area plans under CAA
sections 189a and 189b should apply to plans developed pursuant to CAA
section 189di.e., the plan must include a demonstration including air quality modeling that the control strategy provides for attainment of the PM2.5 NAAQS as expeditiously as practicable.179 For purposes of determining the attainment date that is 179 40

CFR 51.1011b1; 81 FR 58010, 58102.

VerDate Sep<11>2014

17:10 Sep 23, 2021

Jkt 253001

as expeditious as practicable, the state must conduct future year modeling that takes into account emissions growth, known controls including any controls that were previously determined to be RACM/RACT or BACM/BACT, the five percent per year emissions reductions required by CAA section 189d, and any other emissions controls that are needed for expeditious attainment of the NAAQS.
The EPAs PM2.5 modeling guidance 180 Modeling Guidance and Modeling Guidance Update recommends that a photochemical model, such as the Comprehensive Air Quality Model with Extensions CAMx or Community Multiscale Air Quality Model CMAQ, be used to simulate a base case, with meteorological and emissions inputs reflecting a base case year, to replicate concentrations monitored in that year. The model application to the base year undergoes a performance evaluation to ensure that it satisfactorily corroborates the concentrations monitored in that year.
The model may then be used to simulate emissions occurring in other years required for a plan, namely the base year which may differ from the base case year and future year.181 The modeled response to the emissions changes between those years is used to calculate relative response factors RRFs that are applied to the design value in the base year to estimate the projected design value in the future year for comparison against the NAAQS.
Separate RRFs are estimated for each chemical species component of PM2.5, and for each quarter of the year, to reflect their differing responses to seasonal meteorological conditions and emissions. Because each species is handled separately, before applying an RRF, the base year design value should be speciated using available chemical 180 Memorandum dated November 29, 2018, from Richard Wayland, Air Quality Assessment Division, Office of Air Quality Planning and Standards, EPA, to Regional Air Division Directors, EPA, Subject:
Modeling Guidance for Demonstrating Air Quality Goals for Ozone, PM2.5, and Regional Haze, Modeling Guidance, and memorandum dated June 28, 2011 from Tyler Fox, Air Quality Modeling Group, Office of Air Quality Planning and Standards, EPA, to Regional Air Program Managers, EPA, Subject: Update to the 24 Hour PM2.5
NAAQS Modeled Attainment Test, Modeling Guidance Update.
181 In this section, we use the terms base case, base year or baseline, and future year as described in section 2.3 of the EPAs Modeling Guidance. The base case modeling simulates measured concentrations for a given time period, using emissions and meteorology for that same year.
The modeling base year which can be the same as the base case year is the emissions starting point for the plan and for projections to the future year, both of which are modeled for the attainment demonstration. Modeling Guidance, 3738.

PO 00000

Frm 00021

Fmt 4701

Sfmt 4702

53169

species measurementsthat is, each days measured PM2.5 design value must be split into its species components.
The Modeling Guidance provides additional detail on the recommended approach.182
2. Summary of the States Submission As discussed in section IV.C, the SJV
PM2.5 Plan includes a modeled demonstration projecting that the San Joaquin Valley would attain the 1997
24-hour PM2.5 NAAQS by December 31, 2020, based on ongoing emissions reductions from baseline control measures. CARB conducted photochemical modeling with the CMAQ model using inputs developed from routinely available meteorological and air quality data, as well as more detailed and extensive data from the DISCOVERAQ field study conducted in January and February of 2013.183 The Plans primary discussion of the photochemical modeling appears in Appendix K Modeling Attainment Demonstration of the 2018 PM2.5 Plan.
The State briefly summarizes the areas air quality problem in Chapter 2 Air Quality Challenges and Trends and the modeling results in Chapter 5.3
Attainment Demonstration and Modeling of the 2018 PM2.5 Plan. The State provides a conceptual model of PM2.5 formation in the San Joaquin Valley as part of the modeling protocol in Appendix L Modeling Protocol.
Appendix J Modeling Emission Inventory describes emissions input preparation procedures. The State presents additional relevant information in Appendix C Weight of Evidence Analysis of the CARB Staff Report, which includes ambient trends and other data in support of the attainment demonstration.
CARBs air quality modeling approach investigated the many inter-connected facets of modeling ambient PM2.5 in the San Joaquin Valley, including model input preparation, model performance evaluation, use of the model output for the numerical NAAQS attainment test, and modeling documentation.
Specifically, this required the development and evaluation of a conceptual model, modeling protocol, episode i.e., base year selection, modeling domain, CMAQ model selection, initial and boundary condition procedures, meteorological 182 Modeling Guidance, section 4.5, What is the Recommended Modeled Attainment Test for the 24Hour NAAQS.
183 NASA, Deriving Information on Surface conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality, available at https www.nasa.gov/mission_pages/discover-aq/
index.html.

E:FRFM24SEP2.SGM

24SEP2