                 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                  REGION IX 
                             75 Hawthorne Street 
                           San Francisco, CA  94105





Memorandum

To: 	Air Plan Approval; Revisions to the Clark County Ozone Maintenance Plan, Docket ID EPA-R09-OAR-2019-0365

From: 		Karina O'Connor, Air Planning Office, EPA Region 9

Date: 		May 22, 2019

RE: 	Adequacy Documentation for Plan Motor Vehicle Emission Budgets in October 2018 Clark County Revision to Ozone Maintenance Plan

Attached to this memorandum is the adequacy documentation for the "Revision to Motor Vehicle Emission Budgets in Ozone Redesignation Request and Maintenance Plan: Clark County, Nevada" (October 2018) ("2018 Ozone Maintenance Plan Revision"). The 2018 Ozone Maintenance Plan Revision updates certain elements of the approved 2011 Ozone Maintenance Plan for the Clark County ozone planning area for the 1997 ozone national ambient air quality standards (NAAQS), including the attainment inventory, the maintenance demonstration, and the motor vehicle emissions budgets.

The 2018 Ozone Maintenance Plan Revision was submitted by the Nevada Division of Environmental Protection (NDEP) to EPA on October 31, 2018. This memo contains our analysis of the budgets in the 2018 Ozone Maintenance Plan Revision for the Clark County maintenance area for the 1997 8-hour ozone NAAQS. The budgets are listed in the Table 1.

     Table 1  -  Motor Vehicle Emission Budgets (summer, weekday average)
                                  Budget Year
                                   NOx(tpd)
                                   VOC (tpd)
                                     2008
                                     89.50
                                     42.46
                                     2015
                                     90.92
                                     53.94
                                     2022
                                     86.74
                                     52.96


For motor vehicle emissions budgets to be adequate and approvable, they must meet, at a minimum, the EPA's adequacy criteria (40 CFR § 93.118(e)(4)) and be approvable under all pertinent SIP requirements. With respect to maintenance plan, to meet these requirements, the budgets must be consistent with the applicable maintenance requirements and reflect all of the motor vehicle control measures contained in the maintenance demonstration.  Table 2 below contains our analysis of the budgets in the 2018 Ozone Maintenance Plan Revision for each of the adequacy criteria for the Clark County ozone maintenance area.

Based on our evaluation presented in Table 2, we find that the 2018 Ozone Maintenance Plan Revision's motor vehicle emission budgets are consistent with the maintenance demonstration, are clearly identified and precisely quantified, and meet all other applicable statutory and regulatory requirements, including the adequacy criteria in 40 CFR § 93.118(e)(4). For these reasons, the EPA proposes to find adequate and approve the budgets. If we finalize approval of the budgets in the 2018 Ozone Maintenance Plan, as proposed, then they will replace the previously approved budgets from the Clark County's 2011 Ozone Maintenance Plan. 

      Table 2. Evaluation of the Motor Vehicle Emissions Budgets in the 
       Clark County 2018 Ozone Maintenance Plan Revision (October 2018)
                   May 2019 (reviewed by Karina O'Connor)
                           Adequacy Review Criteria
                               (40 CFR part 93)
                                 Is Criterion
                                  Satisfied?
                      Reference in SIP Document/Comments
Sec. 93.118(e)(4)(i)
The plan was endorsed by the Governor (or designee) and was subject to a public hearing.
                                       Y
The October 31, 2018 transmittal letter submitting the 2018 Ozone Maintenance Plan Revision was sent by NDEP's Executive Officer, Greg Lovato, Administrator at the Nevada Division of Environmental Protection, the Governor's designee. The transmittal letter indicates that the Clark County Board of County Commissioners formally adopted the plan on October 16, 2018 following a public hearing on the draft plan.  Clark County Department of Air Quality (DEQ) released its draft plan on August 17, 2018 and requested that public comments be received prior to September 17, 2018. 

Sec. 93.118(e)(4)(ii)
The plan was developed through consultation with federal, state and local agencies; full implementation plan documentation was provided and EPA's stated concerns, if any, were addressed.
                                       Y
Clark County DAQ developed the 2018 Ozone Maintenance Plan Revision in consultation with federal, state and local agencies. These agencies include: EPA Region IX, Federal Highway Administration, NDOT and the Regional Transportation Commission of Southern Nevada (RTC). The draft plan was sent out via email on August 23, 2018.  The methodology was discussed via meetings and emails in May-July of 2018. Issues raised by EPA Region IX staff on the draft plan methodology and draft budgets were discussed by Clark County and EPA in several meetings and addressed by Clark County in the final plan and budgets.
Sec. 93.118(e)(4)(iii)
The motor vehicle emission budgets are clearly identified and precisely quantified.
                                       Y
The budgets for 2008, 2015 and 2022 are clearly identified and precisely quantified in Table 3-1 of the 2018 Ozone Maintenance Plan Revision. The information in Table 3-1 and Appendix A explains how the budgets were quantified, namely, that the budgets represent on-road motor vehicle emission estimates made using the SMOKE-MOVES approach, which incorporates EPA's MOVES2014a emissions rates, SMOKE modeling, fleet data from DMV registration data, CRC vehicle speed data, NDOT HPMS data, travel demand modeling from the Regional Transportation Commission and vehicle classification data from the June 2018 Clark County On-road Vehicle Classification Study.  Section 3-2 describes how the budgets identified in Table 3-1 of the plan were quantified and applied to the budgets. Specifically, 80% of the total safety margin (i.e., the difference between the 2008 attainment inventory and the 2015 and 2022 projected emissions inventory) has been allocated to the on-road motor vehicle emissions.
Sec. 93.118(e)(4)(iv)
The motor vehicle emissions budget(s), when considered together with all other emission sources, is consistent with applicable requirements for reasonable further progress, attainment, or maintenance (whichever is relevant to a given implementation plan submission).
                                       Y
The EPA has concluded that the budgets for 2008, 2015 and 2022 when considered together with all other emission sources are consistent with continuing maintenance of the 1997 8-hour ozone NAAQS through 2022. As documented in NPRM, the EPA is proposing to approve the revisions to the emission inventory and budgets as consistent with applicable requirements for maintenance for the 1997 ozone NAAQS. The 2018 Ozone Maintenance Revision demonstrates continued maintenance with updated emission inventories demonstrating decreasing emissions from the 2008 attainment year out to 2022.  Tables 2-1, 2-2 and 3-1 show how the safety margins support continued maintenance.
Sec. 93.118(e)(4)(v)
The plan shows a clear relationship among the emissions budget(s), control measures and the total emissions inventory.
                                       Y
The 2018 Ozone Maintenance Plan Revision includes updated emission inventories for the years 2008, 2015 and 2022 for all stationary, area, on-road mobile, and non-road mobile sources.  Appendix A of the plan describes the updates to all of these components of the emission inventory and their relation to control measures and the reductions from existing measures. The updated emission inventories incorporating the reductions from adopted measures are given in Tables 5-1 and 5-2 in Appendix A to the 2018 Ozone Maintenance Plan Revision.  
Sec. 93.118(e)(4)(vi)
Revisions to previously submitted control strategy or maintenance plans explain and document any changes to any previous submitted budgets and control measures; impacts on point and area source emissions; any changes to established safety margins (see §93.101 for definition), and reasons for the changes (including the basis for any changes to emission factors or estimates of vehicle miles traveled).
                                       Y
Appendix A of the 2018 Ozone Maintenance Plan Revision describes the revisions to the previously submitted and approved stationary, area, on-road mobile, and non-road mobile sources emission inventories.  MOBILE6.2 was used to develop the motor vehicle emissions in the previously approved 2011 Ozone Maintenance Plan, however the MOVES2014a model, with updated VMT estimates, as well as fleet and speed distribution data for the years 2008, 2015 and 2022 was used in development of the updated motor vehicle emission budgets.  Updated actual emissions information was used to update the point and area source emissions for 2008 and 2015, updated projections and emission factors reduced point and area source emissions in 2022.
Sec. 93.118(e)(5)
EPA has reviewed the State's compilation of public comments and response to comments that are required to be submitted with any implementation plan.
                                       Y
No public comments were received on the 2018 Ozone Maintenance Plan Revision before or during the public hearing on October 16, 2018 (both written and oral). No issues that might have affected our adequacy finding remain unanswered.
                                       




