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Proposed Updates to the Clean Air Construction Standard - Request for Public Comment

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The City of Portland, Multnomah County, Washington County, Metro, and the Port of Portland are proposing updates to the 2018 Clean Air Construction (CAC) Standard, which established diesel engine requirements on agency construction projects to reduce harmful diesel particulate matter emissions.  To summarize, the updates would delay the start of the engine requirements by a year, shorten the overall implementation timeline by one year, and allow expanded use of retrofit devices.  These changes primarily are being proposed in response to current economic and health conditions resulting from the COVID-19 pandemic.   We anticipate the net impact of these changes will be to allow for more effective program implementation while achieving equivalent, or better results in reducing harmful diesel particulate matter. 

More information about the specifics of the proposed updates are available below.  In addition, you may view a recording of the informational session we held on July 8th, where we provided an overview of the proposed changes followed by a question and answer period with attendees.

The public comment on the proposed updates closed July 24, 2020.  The CAC partner agencies are now reviewing received comments and will post a response and next steps over the next few weeks.

Proposed CAC Update Documents

Current 2018 Clean Air Construction Standard

Clean Air Construction Proposed Update Q&A


  • CAC = Clean Air Construction
  • CAC Program = the regional program being developed by the CAC partner agencies to implement the CAC requirements
  • CAC Partner Agencies = City of Portland, Metro, Port of Portland, Washington County, Multnomah County
  • Certified Firms = Disadvantaged, Minority, Women, or Emerging Small Business (DMWESB) or Service Disabled Veteran Business (SDVB) as certified by the State of Oregon Certification Office for Business Inclusion and Diversity.
  • DOC = diesel oxidation catalyst

What Are We Proposing?

  • Delaying the start of the CAC nonroad engine requirements by one year.  The first nonroad engine requirement is currently set to take effect on 1/1/2021.  We are proposing pushing that out to 1/1/2022. The Tier 1 nonroad engine restriction effective date would also be pushed out one year to 1/1/2023. We would then collapse the Tier 2 and 3 nonroad engine restriction effective date into the same year, 2024, which was the original year for the Tier 3 restriction.  The final, Tier 4 only nonroad engine requirement (no DOC retrofitted devices, except for certified firms) would be moved up to 2025. It also allows for DPF-retrofitted equipment indefinitely, as opposed to phasing-out retrofitted equipment.   DPFs remove diesel particulate matter to the same degree as Tier 4 engines.
  • For on-road concrete mixers and dump trucks, we propose prohibiting pre-2007 engines unless retrofitted with a DPF, starting January 1, 2024.  We would allow an exemption for certified firms that retrofitted their on-road concrete mixer or dump truck with a DOC prior to 2024.  This removes a previous, temporary allowance for some DOC-retrofitted vehicles owned by non-certified firms.  It also allows for DPF-retrofitted vehicles indefinitely, as opposed to phasing-out retrofitted vehicles.

Why Are We Taking this Action? – Why the Initial One-Year Implementation Delay in the Engine Requirements?

  • The current COVID-19 crisis has affected the roll-out of the Clean Air Construction program in a few critical ways:
    • It has delayed the City’s on-site technical assistance to certified DMWESB/SDVB firms, designed to help those firms assess their fleet against the CAC requirements and plan for coming into compliance
    • It has delayed other contractor outreach opportunities previously planned for the busy conference and networking season that typically starts in April-May. 
    • Even though construction continues to happen during the COVID-19 crisis, those firms are currently operating under additional stress.  Delaying the start of the nonroad engine requirements, and making up for the lost time later, gives firms – especially smaller firms, one less pressure right now during a stressful time.
    • For some public agencies, construction projects are being deferred due to heavily impacted agency budgets.
    • It is likely that planned, direct financial assistance to certified DMWESB/SDVB firms from partner agencies will no longer be available due to budget shortfalls.  This means that direct financial assistance will have to largely come from grants.  The State’s related grant program authorized under HB2007 (2019) should launch in Spring 2021.  Delaying start of the CAC nonroad engine requirements by one year will allow firms the time to apply for and receive grant-based financial assistance, and take the related actions.
  • There was an administrative delay during 2019 related to soliciting the software that will be needed for the CAC online registration and compliance database.  The solicitation for that software is currently underway, but will not be up and running in time for a 1/1/2021 launch date.

Why Are We Taking this Action? – Why the Collapsed and Shorter Overall Timeline?

Air quality plays a role in an individual’s ability to fight diseases that target the respiratory system.  We have seen this play out during the current COVID-19 pandemic, and people of color are disproportionately impacted.  We are proposing compressing the CAC Standard timeline to balance the logistical need to delay the initial implementation of the CAC engine requirements with the crucial need to improve our local air quality. 

How Will the Proposed Timeline Revision Affect Air Quality?

  • It will initially delay emissions reductions associated with this effort by one year; however, we will make up the delay by compressing the engine requirements timeline and reducing the overall timeline by one year. 
  • Also, the impact on emissions reductions from delaying the start of the program will be moderated by economy-driven project deferrals.  Many projects will now be starting during more advanced phases of the program.  We anticipate the net impact of these program changes will be to achieve equivalent or better diesel particulate matter reductions. 

How Will the Proposed Timeline Revision Affect Contractors?

  • It initially gives contractors an additional year to plan for these requirements, as the first engine requirement/restriction begins in January 2022 instead of 2021.  This delay also gives contractors access to related grant programs during 2021, such as the State’s VW-Settlement related grant funds, prior to the first engine requirement going into effect.
  • It allows the use of DPF-retrofitted equipment into perpetuity (regardless of when the DPF was installed or the age of the engine), thus preserving that investment made by contractors.
  • It requires contractors to achieve the CAC Standard end goal one year earlier than what is currently in the CAC Standard.  

How Will the CAC Program Use this Time?

  • Develop online training, education, and outreach tools (including tools in multiple languages)
  • Once we are able, conduct in-person contractor outreach and education.
  • Once we are able, fully launch the City’s on-site technical assistance program to certified DMWESB/SDVB firms.
  • Develop and test the CAC online registration and compliance database.
  • Recruit more regional public agencies to join the CAC Program.


Stacey Foreman

Sustainable Procurement Program Manager