CEQA  / Air Quality Tech Reports

Air Quality Tech Reports

The California Environmental Quality Act (CEQA) brings together many important aspects of project planning, and in some cases can affect project design.  For industrial projects in particular, preparing an Air Quality Technical Report that is appended to the CEQA Mitigated Negative Declaration (MND) or Environmental Impact Report (EIR) is a typical practice. Yorke Engineering, LLC (Yorke) is very familiar with preparing air quality documents and air quality technical analysis to support the CEQA process.  With over 300 years of combined staff environmental experience and over 350 satisfied customers, Yorke is dedicated to assisting industry and government with critical project needs, including the preparation of Air Quality Technical Reports for CEQA.

Yorke staff routinely perform analyses to assess a project’s potential impacts to air quality, public health, climate change, and/or odors in support of CEQA documents.  These analyses typically consist of some or all of the following components: background air quality/climate and regulatory discussions, emission estimates, dispersion modeling, health risk assessment (HRA), greenhouse gas (GHG) emission impacts on climate, and/or odor analyses.  The Technical Reports provide documentation of the methodologies used and results obtained in comparison to significance criteria for each type of impact analyzed.  Links with additional details on emissions calculations and air quality impact assessments are provided below.  Links on Health Risk Assessment, GHG Impacts Analysis, and Odor Analysis are provided under the CEQA Services Menu on this web site.

Emissions Calculations – Air emission quantification is a central component of any air quality inventory analysis. Emissions from project construction and operation generally reflect the information provided in the project description.  For large projects, emissions from alternatives to the proposed project may also need to be estimated.  As such, the estimated amount of criteria pollutants, toxic air contaminant (TACs), and GHGs emitted by a project – in combination with other factors – determines whether a project could have a significant impact on air quality, including health risks or odors.  For the past 10 years, regulations have increasingly required projects to inventory future GHG emissions due primarily to fossil fuel combustion. As a result, methods are now established that provide a defensible quantification approach to determine impacts related to climate change. Yorke has experience with current emissions estimation techniques and models, including EPA emission factors, CalEEMod, EMFAC, OFFROAD, and other custom emissions models.  Click on Emissions Calculations above for additional details.

Air Quality Impact Analyses – In many cases, the potential for a project to have significant impacts on air quality can be determined based on the mass emission estimates alone, as mass -based significance criteria have been defined for most areas in California.  However, for more complex projects, projects which could have a significant localized impact, and/or projects where the mass-based significant criteria may be too conservative, air dispersion modeling can be applied.  Air dispersion modeling is the primary analysis method used for predicting ground-level concentrations based on a source emission rate to determine compliance with ambient air quality standards.  The results of air dispersion modeling are also used as the input to HRA calculations which determine health risks based on predicted concentrations of the individual TACs combined with health risk factors.  Yorke understands the uses of various dispersion modeling functions – from screening to refined – to estimate downwind air pollutant concentrations and how to apply these results to air quality impact assessment. The level of health risk assessment and the methods used to evaluate air toxic emissions can vary considerably depending on the toxicity of the air pollutants being emitted, pollutant mass emission rate, and distances to the nearest receptors.  Click on Air Quality Impact Analyses above for additional details.

Significance Criteria and Determinations – The role of CEQA is to evaluate potential environmental impacts and to inform the permitting agencies and the public of these impacts during the progressive stages of project planning and approval. Agencies have adopted “significance thresholds” that are to be used by project proponents to assist the permitting and approval agencies with determining the scale of impacts related to the proposed action. Air quality and climate-related CEQA thresholds are unique compared to other environmental impacts because they are typically numeric, which provides a quantitative boundary for evaluating project significance.  Air quality and climate change thresholds may be based on mass emission rates, health risk impact levels, air pollutant concentrations, or performance standards.  Once the significance of the impact is mathematically determined, the Air Quality Technical Report is prepared.  If the impacts are determined to be significant, then additional work may be needed to reduce the impacts by applying further mitigation measures until the project can be shown to have a less than significant impact on air quality or climate change.  Click on Significance Criteria and Determinations above for additional details.

Since Yorke specializes in air quality regulations and project planning in California, the primary benefit to the project developer is high-quality air technical analyses leading to defensible CEQA documents. If your project requires local California Air District permitting, it is also more cost-efficient and saves time to have Yorke do both the air quality section of the CEQA documents and the air permit applications, since there is significant overlap in the air quality analysis required. A few of the other benefits our customers experience are listed below:

  • Presentation to CEQA Lead Agencies
  • Consistent CEQA and Air Permitting Analyses
  • California Air District Relationships
  • Teamwork and Solid Communication
  • Streamlined Emissions Analysis
  • Improved Design Mitigation and Control Features