DAQ-2024-008992

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UTAH STATE IMPLEMENTATION PLAN 4
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SECTION X 6
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VEHICLE INSPECTION 8
AND MAINTENANCE PROGRAM 9
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PART B 13
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DAVIS COUNTY 15
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Adopted by the Utah Air Quality Board 36
February 7, 202437

Section X Part B, Page i
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Table of Contents 6
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1. Applicability ............................................................................................................................................................. 1 9
2. Summary of Davis County I/M Program ................................................................................................................... 2 10
3. I/M SIP implementation ............................................................................................................................................. 3 11
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Section X Part B, Page ii
SECTION X, PART B 1
DAVIS COUNTY 2
Appendices 3
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1 Davis County Ordinance 10.12.1 Davis County Vehicle Emissions 7
Inspection/Maintenance Program, approved and adopted June 13, 2023 8
effective date July 1, 2023. 9
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Section X Part B, Page 1
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UTAH STATE IMPLEMENTATION PLAN 2
SECTION X 3
AUTOMOTIVE INSPECTION AND MAINTENANCE (I/M) PROGRAM 4
PART B 5
DAVIS COUNTY 6
1. Applicability 7
Davis County Inspection and Maintenance (I/M) Program Requirements: The Utah Air Quality 8
Board adopted an ozone maintenance plan for Salt Lake and Davis counties on November 5, 9
1993, to address the 1979 1-hour Ozone National Ambient Air Quality Standard (NAAQS). The 10
plan was reorganized and adopted on January 5, 1995. Revisions to the ozone maintenance plan 11
were adopted by the Board on June 5, 1996, and June 7, 1997. The Environmental Protection 12
Agency (EPA) approved the plan on July 17, 1997 (62 FR 38213, July 17, 1997). The ozone 13
maintenance plan required implementation of an improved I/M program no later than January 1, 14
1998. The ozone maintenance plan established a performance standard that was more stringent 15
than the federal Basic I/M Performance Standard. 16
On July 17, 1997, EPA approved the state’s request to redesignate Salt Lake and Davis counties 17
to attainment for the 1979 1-hour ozone standard. As part of that action, EPA approved the 18
state’s 1-hour ozone maintenance plan (62 FR 38213). On July 18, 1997, EPA promulgated an 8-19
hour ozone NAAQS of 0.08 ppm (62 FR 38894). This standard was intended to replace the 1-20
hour ozone standard. On April 30, 2004, EPA designated areas of the United States for the 1997 21
8-hour ozone standard (69 FR 23857). EPA designated all areas in Utah, including Salt Lake 22
County and Davis County, as unclassifiable/attainment for the 1997 8-hour ozone NAAQS (69 23
FR 23940). 24
On April 30, 2004, EPA revoked the 1979 1-hour ozone NAAQS (69 FR23951, 23996; 40 CFR 25
50.9(b). As part of that rulemaking, EPA established certain requirements to prevent backsliding 26
in the areas that were redesignated to “attainment” but subject to a maintenance plan, as is the 27
case for Salt Lake and Davis County. These requirements are codified at 40 CFR 51.905. In the 28
case of Utah, one of these requirements was to submit a maintenance plan for the 1997 8-hour 29
ozone standard. On March 22, 2007, the Governor of Utah submitted a maintenance plan for the 30
1997 8-hour ozone standard for Salt Lake and Davis County, and associated rule revisions, which 31
included an I/M program as a control measure. This plan was approved by EPA on September 32
26, 2013 (78 FR 59242). 33
On October 26, 2015, the EPA promulgated a revision to the primary NAAQS for ground level 34
ozone (80 FR 65292), lowering the standard to 0.070 ppm for the 4th highest daily 8-hour 35
concentration. Davis County was designated as a “marginal” nonattainment area for the 2015 8-36
hour ozone standard effective August 3, 2018 (83 FR 25776, June 4, 2018). 37

Section X Part B, Page 2

On October 7, 2022, the EPA finalized the reclassification of the Northern Wasatch Front 1
nonattainment area, including Davis County, from marginal to moderate status for the 2015 2
standard. The reclassification to moderate status became effective on November 7, 2022 (87 FR 3
60897). With this redesignation to moderate nonattainment, Davis County is required by Sections 4
182 and 187 of the CAA to implement and maintain an I/M program in Davis County that met 5
the minimum requirements of 40 CFR Part 51 Subpart S and that was at least as effective as the 6
EPA's Basic Performance Standard as specified in 40 CFR 51.352. Parts A and B of Section X, 7
together with the referenced appendices, demonstrate compliance with the CAA and 40 CFR Part 8
51 provisions for Basic I/M Performance Program Requirements for Davis County. In addition, 9
the Davis County I/M program is a control measure included in the Salt Lake City 24-hour 10
particulate Serious SIP submitted to EPA on February 15, 2019. 11
2. Summary of Davis County I/M Program 12
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Below is a summary of Davis County’s I/M program. Section X, Part D Appendix 1 contain the 14
essential documents for Davis County’s I/M program. 15
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Network Type: Davis County’s I/M program is a decentralized, test-and-repair network. 17
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Test Convenience: There are approximately 140 permitted I/M stations within Davis 19
County. Specific operating hours are not specified by the county. Some stations that test 20
and/or service only one type of vehicle are permitted. There are also government and 21
private fleet permitted stations that are not open to the public. 22
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Subject Fleet: All model year 1968 and newer vehicles registered or principally-operated 24
in Davis County, are subject to the I/M program except for exempt vehicles. 25
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Test Frequency: Vehicles less than two years old as of January 1 on any given year are 27
exempt from an emissions inspection. Vehicles two years old and less than six years old 28
as of January 1 on any given year, are inspected every other year as per Utah Code 41-6a-29
1642(6). All vehicles six years or older as of January 1 on any given year, are inspected 30
annually. 31
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Station/Inspector Audits: Davis County’s I/M program will regularly audit all permitted 33
I/M inspectors and stations to ensure compliance with county I/M ordinance and policies. 34
Particular attention will be given to identifying and correcting any fraud or incompetence 35
with respect to vehicle emissions inspections. Compliance with recordkeeping, document 36
security, analyzer maintenance, and program security requirements will be scrutinized. 37
Davis County I/M program will have an active covert compliance program to minimize 38
potential fraudulent testing. 39
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Section X Part B, Page 3

Waivers: Davis County’s I/M program may issue waivers under limited circumstances. 1
The wavier procedure can be found in Davis County’s I/M ordinance provided in 2
Appendix 1. Davis County will take corrective action, as needed, to maintain a maximum 3
waiver rate of 1% of the initially failed vehicles, or the Utah Air Quality Board will revise 4
the SIP and emission reductions claimed based on the actual waiver rate. The conditions 5
for issuing waivers are specified in Davis County’s I/M ordinance and meet the minimum 6
waiver issuance criteria specified in 40 CFR Subparts 51.360. 7
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Test Equipment: Specifications for Davis County’s emission analyzer and its I/M test 9
procedures, standards, and analyzers are provided in Davis County’s I/M ordinance 10
provided in Appendix 1. Test equipment and procedures were developed according to 11
good engineering practices to ensure test accuracy. Analyzer calibration specifications 12
and emissions test procedures meet the minimum standards established in Appendix A of 13
the EPA's I/M Guidance Program Requirements, 40 CFR Part 51 Subpart S. 14
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Test Procedures: 16
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• The following vehicles are subject to an OBD II inspection: 18
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o 1996 and newer non-diesel motor vehicles <8501 lbs. Gross Vehicle 20
Weight Rating (GVWR); 21
o 2008 and newer non-diesel motor vehicles between 8,501-14,000 lbs. 22
GVWR; and 23
o 1998 and newer diesel-powered motor vehicles <14,000 lbs. GVWR, if 24
equipped with OBDII. 25
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• The following vehicles are subject to a two-speed idle test that is compatible with 27
Section VI (Preconditioned Two Speed Idle Test) in Appendix B of the EPA I/M 28
Guidance Program Requirements, 40 CFR 51, Subpart S: 29
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o 1995 and older non-diesel motor vehicles, 31
o 1996 to 2007 non-diesel motor vehicle >8,500 lbs. GVWR; and 32
o 2008 and newer non-diesel motor vehicles > 14,000 lbs. GVWR. 33
• The following vehicles are subject only to a visual inspection: 34
o 1998- 2007 diesel powered motor vehicles < 14,000 lbs. GVWR, if not 35
equipped with OBDII. 36
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3. I/M SIP Imple mentation 40
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Section X Part B, Page 4

The I/M program ordinance, policies, procedures, and activities specified in this I/M SIP 1
revision have been implemented and shall continue until a maintenance plan without an 2
I/M program is approved by the EPA in accordance with Section 175 of the Clean Air Act 3
as amended. 4