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CEQA Modeling

Modeling Under CEQA

Ashworth Leininger Group’s health risk assessment (HRA) practice leverages our expertise in air toxics emissions inventory development, best available control technology for toxics (T-BACT) determination, and air dispersion modeling on behalf of industrial and regulatory clients.


As illustrated below, ALG has the capabilities to:

  • Develop defensible toxic air contaminant (TAC) emission inventories under the California Air Toxics Hot Spots Program (AB 2588);

  • Use Geographic Information System (GIS) to develop key input data for HRAs;

  • Perform air dispersion modeling consistent with EPA, ARB, and local air district modeling guidelines;

  • Execute health risk assessment models that use the source emission rates developed in the emission inventory task and the output of the air dispersion modeling to quantify potential health effects;

  • Prepare comprehensive HRA reports; and

  • If necessary, provide assistance in making T-BACT determinations and developing Risk Reduction Plans

CEQA Modeling Project Examples


ALG has conducted health risk assessments and other environmental modeling to support CEQA/NEPA determinations; examples include:

Diesel-Fuel Truck Evaluation

Evaluated potential health risks to determine the feasibility of a project that would greatly increase the number of diesel-fueled heavy-duty truck trips to an existing industrial facility in southern Los Angeles County. Followed California Air Resources Board and South Coast Air Quality Management District risk assessment protocols for determining mobile source diesel particulate matter emissions and their associated health effects;

Refinery Fuel Reformulation

Assisted with an Environmental Impact Report (EIR) for additions and modifications to a California refinery necessary to produce reformulated gasoline required by the federal Clean Air Act Amendments and the California Air Resources Board. Supervised emissions calculations and directed air dispersion modeling and human health risk assessment. Assisted refinery in negotiating with the South Coast Air Quality Management District as lead agency for the EIR, including development of modeling protocols.

Modified Ski Resort Emissions

Prepared Air Quality Impact Analysis (AQIA) in support of a third party EIR for proposed expansion of the ski resort. Analyses included modeling of power plant emissions, including a health risk assessment for diesel engine exhaust; modeling of wood smoke emissions; and modeling of carbon monoxide emissions from resort traffic. A cumulative impact analysis was also performed for particulate emissions

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