PM2.5 State Implementation Plans (SIPs)
2018 State of the Environment Report (AQ)

A State Implementation Plan (SIP) is a state plan to reduce air pollution in areas that do not meet National Ambient Air Quality Standards (NAAQS). Each state is responsible for developing plans to demonstrate how the NAAQS will be achieved, maintained, and enforced. The plans and rules associated with them are enforced by the state, and after federal approval, are also federally enforceable. These plans are the framework for each state’s program to protect the air.

In 1997, the EPA strengthened the 24-hour standard for PM2.5, lowering it from 65 micrograms per cubic meter (µg/m3) to 35µg/m3. Prior to this change, Utah was in compliance with the 24-hour standard. The new standard went into effect in December 2006. In November 2009, the EPA determined that three areas in Utah were unable to meet the revised 24-hour PM2.5 standard, which required the state to prepare State Implementation Plans (SIPs) for each nonattainment area. These plans ultimately became Utah’s Moderate Area SIPs. Each plan included an assessment of the likelihood of attaining the 24-hour NAAQS by 2015.

The revised plans for both the Salt Lake City (1.8 MB) and Provo (1.79 MB) nonattainment areas showed that it would be impracticable to attain the standard by the end of 2015. The Logan SIP, however, demonstrated that attainment could likely be achieved by 2015.

When the EPA made its determinations (298.81 KB) for each nonattainment area, it found that neither the Salt Lake City nor the Provo area demonstrated attainment by December 2015. This finding effectively reclassified both areas from Moderate to Serious as of June 9, 2017. The final determination for the Logan area was postponed pending further analysis of the monitored data. Following that analysis, EPA determined that the Logan area had attained the standard by December 2015.

The re-classifications meant that Utah would need to complete new SIP revisions for the Salt Lake and Provo nonattainment areas and demonstrate attainment of the PM2.5 standard by December 31, 2019. The PM2.5 Implementation Rules (1.12 MB) issued by the EPA on August 24, 2016, shaped the development of these plans.

Control Strategies

A reclassification to Serious moves the benchmark for emission controls from “Reasonable” to “Best Available.” This change impacts point, area, and mobile sources. A Serious Area nonattainment plan must include provisions for the implementation of best available control measures and technologies (BACM/BACT). These provisions include enforceable emission limitations as well as schedules and timetables for compliance.

Point sources

Point sources emitting, or having the potential to emit, at least 70 tons per year (tpy) of PM2.5 or any of its precursors were reviewed to ensure all controls meet Best Available Control Measures (BACM), including Best Available Control Technology (BACT). Where it was determined that existing controls were no longer sufficient, the corresponding emission limits and/or operating conditions enumerated in the SIP were revised accordingly. The limits and operating conditions that apply specifically to certain point sources appear in Section IX Part H (1.51 MB) of the SIP.

Area Sources

DAQ had already developed and reviewed area-source rules for the Moderate SIP to ensure they met reasonably available control measure (RACM) requirements. As part of the Serious SIP, the division has re-evaluated these rules to ensure they meet the more stringent BACM requirements and modified them where appropriate. Numerous area-source rules are currently included in the Serious SIP.

Success Story: Wood Stove Conversion Program


In December 2017, the Environmental Protection Agency (EPA) awarded Utah over $9.5 million in funding through Targeted Airshed Grants to reduce pollution from wood stoves. DAQ made this funding available in October 2018 to help residents, particularly low-income households, convert their wood stoves and fireplaces to cleaner-burning devices.

Originally scheduled as a five-year program, demand has outpaced funding, and the program will end well before the five-year mark. Funding for woodstove conversions in the Salt Lake Nonattainment Area (NAA) was completely allocated on the first day DAQ began accepting applications. Voucher dollars for the Provo NAA were allocated within a week.

The stove-conversion program targets wood-burning devices in Utah’s three nonattainment areas: Salt Lake, Provo, and Logan. The program covers Box Elder, Cache, Davis, Salt Lake, Tooele, Utah, and Weber counties. Although EPA recently determined that Logan was in attainment for the 24-hour PM2.5 National Ambient Air Quality Standards (NAAQS), wood-burning remains a major contributor to particulate pollution in the Cache Valley. Wood-stove conversions will help ensure the area maintains its attainment designation.

The airshed grants target low-income households, with lower rebates offered to other households. Residents have four options:

  • Exchange an operational woodstove (including a pellet stove) for a gas stove (natural gas or propane)
  • Convert a fireplace to a gas fireplace (natural gas or propane).
  • Exchange an operational, uncertified wood stove for an EPA-certified wood stove
  • Turn in an operational wood stove or insert for recycling.

DAQ issues a rebate voucher for applications that meet the program requirements. Vouchers can be used at DAQ-approved vendors towards the purchase of a qualifying device.

Rebate Amounts for the Wood-smoke Reduction Program

OptionDevice change-outRebate Amount Low-income householdsRebate Amount Non-low-income households
1Any woodstove/insert or open fireplace to natural gas- or propane-fueled stove/insert$3,800$2,800
2Uncertified woodstove/insert  to EPA-certified woodstove/insert$500$500
3Bounty for destroying a woodstove$250$250

Fine particulate (PM2.5) from wood-burning contributes to respiratory and other health problems. While cars emit the majority of the precursor gases that form fine particulate, wood-burning emits these particles directly into the air. Replacing an old, uncertified woodstove with an EPA-certified stove can reduce the fine particulate emitted through wood-burning by 60 percent. Converting an uncertified woodstove to a natural-gas stove provides even greater benefits, reducing particulate pollution by 99.9 percent.

Response to the program has exceeded all expectations. Since the program began, DAQ has issued the following number of vouchers (by nonattainment area):

  • Salt Lake: 725
  • Provo: 552
  • Logan: 353 (DAQ will issue another 200-300 vouchers as applications are received)

Residents within the Salt Lake and Provo NAAs can be placed on a waiting list for unclaimed or unused vouchers. The current wait list for the Salt Lake NAA is 1,400, with the Provo NAA not far behind. DAQ intends to apply for additional funding for the Salt Lake NAA to help meet the overwhelming demand.

DAQ received many positive comments about the program from participants.

 “The wood stove conversion program is a win-win for everyone: the homeowners who swapped out their smoky stoves, their neighbors, and all the residents of the Wasatch Front. I hope it can continue in future years until everyone who wants to participate has done so.”

— Paul Corrigan 

Finally having a warm spot in our house that’s not also filled with firewood and/or wood smoke might mean I won’t get anything done this winter.”

— Kate Corrigan

Mobile Sources

Mobile source controls already include Tiers 2 and 3 of the federal motor-vehicle-control program as well as vehicle inspection and maintenance (I/M) programs. Transportation-related conformity requirements will become part of the Serious Area SIPs and affect Metropolitan Planning Organizations (MPOs) in their respective nonattainment areas. PM2.5-related emission goals known as Motor Vehicle Emission Budgets (MVEBs) will be included in each SIP. To receive federal funding, each MPO will need to demonstrate conformity with these MVEBs as part of the SIP’s transportation-planning requirements.

Success Story: Employer-Based Trip Reduction (EBTR)

Using public transit helps to reduce emissions across the city.

DAQ began hosting a series of meetings in 2017 to provide companies and employees with vehicle trip-reduction strategies and other mobile-related emissions measures. Implementation of these measures can help companies:

  • Reduce their contribution to poor air quality.
  • Provide benefits to their employees.
  • Reduce company costs associated with transportation.

Since vehicle emissions are responsible for the majority of the ozone and PM2.5 in Utah, DAQ is pleased that many companies throughout the state are taking voluntary steps to reduce their vehicle emissions.

The EBTR series is now presented exclusively through webinars and serves as a way to help employers identify vehicle emission-reduction strategies that work for their companies.

The EBTR Webinar Series has been timely and excellent in providing information, making connections, and understanding what is happening at other businesses and organizations. It has been a great platform for learning from others about their experiences and new possibilities. I look forward to future presentations.”

— Steven Bergstrom, Director, Office of Sustainability, Intermountain Healthcare

State Implementation Plan (SIP) Status


Part of the technical work that underlies any SIP is the consideration of monitored air quality. Review of these data shows that the Provo area is attaining the 24-hour PM2.5 standard with its two most recent 3-year averages (2014–2016, and 2015–2017). This allows EPA to apply a Clean Data Determination to the area and effectively suspend many of the required SIP elements.

There are several elements that DAQ must still develop and submit:

  • A base-year emissions inventory
  • Provisions to ensure BACM/BACT
  • New source review (NSR) provisions that specifically address PM5 and its precursors in the nonattainment area.

DAQ completed each of these elements during the summer of 2018. All other Serious Area SIP elements will remain suspended until the area is redesignated to attainment, after which these requirements would be permanently discharged. If EPA determines that the area has re-violated the PM2.5 NAAQS, Utah would need to submit these elements by a future date to be determined by the EPA.

Salt Lake

The Serious Area SIP for the SLC nonattainment area has been developed by DAQ and proposed for public comment. The Serious SIP includes a demonstration, including air-quality modeling, that the area can likely attain the 24-hour PM2.5 standard by 2019. The SIP also includes provisions to ensure best available control measures and technologies (BACM/BACT) throughout the nonattainment area.

DAQ must still address the comments made during the November 2018 period of public review (1.51 MB) and bring the plan back the Utah Air Quality Board with any revisions derived from these comments. DAQ anticipates this work will be completed by January 2019.


Effective October 19, 2018, EPA determined that the Logan area had attained the 24-hour NAAQS by December 2015 as required. This means that the nonattainment area remains classified as Moderate, and it will not be necessary for DAQ to make SIP revisions to address Serious Area planning requirements. EPA also used a Clean Data Determination to establish that any elements still outstanding from the Moderate Area SIP will also be suspended until the area is redesignated to attainment or EPA determines that the area has re-violated the 24-hour PM2.5 NAAQS.

On November 23, 2018, EPA announced it was finalizing approval (247.1 KB) of the emissions inventory, modeled attainment demonstration, determination for Reasonably Available Control Technology (RACT), determination for On-Road Mobile Sources Reasonably Available Control Measures (RACM), and determination for the Cache County Inspection and Maintenance (I/M) Program, among other measures. This final rule approving the Logan SIP was effective December 24, 2018.

Success Story: Logan Attainment Designation

Logan Attainment Designation.

EPA’s determination this fall that the Logan PM2.5 nonattainment area meets the conditions for attainment makes it the first PM2.5 nonattainment area in the state to reach attainment since the standard was tightened 12 years ago. The Logan area currently meets the 2006 24-hour PM2.5 federal standard of 35 micrograms per cubic meter (µg/m3) based on certified air-monitoring data from 2015-2017.

When monitored air-quality data in a designated nonattainment area shows the area meets the National Ambient Air Quality Standards (NAAQS)  EPA suspends the submission of certain State Implementation Plan (SIP) requirements as long as the area continues to meet the standard. Under this Redesignation and Clean Data Policy (CDP), the following will no longer be required for the Logan area:

  • Reasonable further progress (RFP) requirements
  • Attainment demonstrations
  • Contingency measures
  • Other state planning requirements related to attainment of the NAAQS

DAQ, county officials, and the Bear River Health Department worked collaboratively to develop a plan to reduce emissions and secure funding for targeted emission reductions. A vehicle emissions-testing program, wood-burning restrictions, projects funded through EPA Targeted Airshed Grants, and behavior changes by Cache Valley residents are credited with air-quality improvements in the nonattainment area.

Emissions Testing Program

In 2013, Cache County officials drafted their first-ever emissions-testing program. The program began in 2014 and requires vehicles older than six or more model years to obtain a smog certificate every other year. Vehicles manufactured in or before 1968 are exempt, as are vehicles during their first five model years. Unlike other I/M programs throughout the state, the Cache I/M program established a $15 or $20 cap on the cost of an inspection, depending on the type on inspection needed, making it the most cost-effective program in the state. The Bear River Health Department oversees the program.

Targeted Airshed Grants

EPA’s Targeted AirShed Grant program helps state and local agencies implement projects that reduce air pollution in nonattainment areas with the highest levels of PM2.5  and ozone. In 2016, EPA awarded a $2.5 million Targeted Airshed Grant to DAQ) to replace school buses in Cache and Utah Counties and fund a program in Cache County to help qualifying owners repair or replace vehicles that fail emissions testing. The Cache County Vehicle Repair and Replacement Assistance Program (VRRAP) provides funding assistance to individuals whose vehicle fails vehicle emission-testing to replace their vehicle with a newer, cleaner one or repair it. The amount of financial assistance depends on household income, household size, and whether the applicant chooses to replace or repair the failed vehicle. Financial assistance can be as high as $5,000 for a vehicle replacement or $1,000 for a repair.

In 2018, DAQ received more EPA funding for two projects in Cache County through the Targeted Airshed Grant program:

  • The Logan Wood-burning Appliance Changeout Project received approximately $3.2 million to reduce residential wood-smoke emissions by changing out uncontrolled wood-burning appliances with gas or propane heating appliances, replacing uncertified wood stoves/inserts with EPA-certified wood-burning units, and removing uncertified wood-stoves/inserts.
  • The Logan Heavy-Duty Diesel Vehicle Replacement Project also received approximately $3.2 million to provide rebates to replace 1999-2006 model-year medium- and heavy-duty diesels with trucks that meet the most stringent emissions standards.

Cache Clean Air Consortium

The Cache Clean Air Consortium was formed in early 2013 by a small group of concerned citizens to improve air quality within Cache Valley and northern Utah. Since then, the consortium has grown and expanded its outreach to include idle-free campaigns at local schools, clean-air conferences, and collaborative efforts that lead to meaningful air-quality changes at the local level.